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Seismic isolation by rubber–soil mixtures for developing countries

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Abstract

This paper proposes a promising seismic isolation method particularly suitable for developing countries, which makes use of rubber–soil mixtures. Apart from reducing the level of shaking in the horizontal direction, the distinctive advantage of the proposed method is that it can also significantly reduce the shaking level of vertical ground motion, to which an increasing attention has been paid in the earthquake engineering community. On the other hand, the use of scrap tires as the rubber material can provide an alternative way to consume the huge stockpile of scrap tires all over the world. Moreover, the low cost of this proposed seismic protection scheme can greatly benefit those developing countries where resources and technology are not adequate for earthquake mitigation with well-developed, yet expensive, techniques. The proposed method has been demonstrated through a series of numerical simulations and a parametric study has also been carried out. Lastly, five important issues regarding the concept and feasibility have been discussed. Copyright © 2007 John Wiley & Sons, Ltd.

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... Although it has existed as a concept among seismic isolation approaches for a long time, the isolation method suggested by Tsang [1] was first introduced into the literature with the definition of 'Geotechnical Seismic Isolation (GSI)'. This innovative approach was previously proposed by researchers with the idea of laying a synthetic layer under the building foundations and distributing earthquake energy [2,3]. ...
... Similarly, studies were also carried out on reducing horizontal ground movements by using geotextile between soil layers [4]. However, the GSI method became prominent with the modeling of the RSM layer under the foundation of a 10story building for seismic isolation (Fig. 1) [1]. It is stated that with the use of the RSM layer, not only the horizontal movement is damped, but also the vertical movements are limited. ...
... Regarding the content and applicability of the method; it was also underlined that factors such as nonlinear soil behavior, resonance effects of the soil, liquefaction, ground settlement, and environmental effects should be evaluated. In subsequent studies, comprehensive numerical and experimental studies were carried out on the seismic isolation capacity of RSM layers formed with varying rubber contents [1,[5][6][7][8][9][10]. [1] Another example of the GSI method is developing an isolation layer using geosynthetic material with or without an RSM layer. ...
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Seismic isolation is a method of protecting buildings from earthquake-induced deformations by using isolators and devices under the superstructure. The purpose of the seismic isolation method is to reduce the earthquake forces transferred from the ground to the structure by placing energy-absorbing elements between the foundation and superstructure. Especially in developing countries, the "Geotechnical Seismic Isolation (GSI)" system has been proposed as an isolation method to reduce earthquake-induced damages on buildings. This study, it is aimed to reduce the effects of earthquakes in a multi-story building with an isolation layer formed by a rubber-sand mixture (RSM). For this purpose, a 10-story reinforced concrete building was numerically modeled. Beneath the foundation of the building model, a seismic energy absorbent RSM layer was placed and its contact with the natural soil was interrupted by using geosynthetic liners. The model was subjected to the 1992 Erzincan (EW) Earthquake motion and its performance has been evaluated in terms of lateral displacements and accelerations. The numerical studies indicated a substantial improvement due to the use of the RSM layer. The accelerations measured by the superstructure decreased up to 48% by employing the isolation layer. The numerical analysis was carried out using the dynamic module of the PLAXIS 2D finite element analysis program.
... Earthquake energy can also be dissipated by reducing the rocking stiffness (Tsang and Pitilakis 2019), taking the advantages of rocking isolation, which is a well-known seismic isolation technique (Anastasopoulos et al. 2012;Acikgoz and DeJong 2014;Bantilas et al. 2021;Makris 2014;Shang et al. 2020;Sorace and Terenzi 2015). Researchers have used various types of low-modulus material, such as sand (Anastasopoulos et al. 2012;Banović et al. 2018b;Patil et al. 2016;Radnić et al. 2015), sand-bitumen mixtures (Kuvat and Sadoglu 2020), gravel (Pecker 2003;Pecker et al. 2001;Steenfelt et al. 2015), stone pebbles (Banović et al. 2018a(Banović et al. , 2019(Banović et al. , 2020a(Banović et al. , 2020bBanović 2021), rubber-soil mixtures (Brunet et al. 2016;Forcellini 2017, Forcellini 2020Forcellini 2021;Hernández et al. 2020;Mavronicola et al. 2010;Pitilakis et al. 2021;Tsang 2008;Tsang 2009;Tsang et al. 2012;Tsang et al. 2020;Tsiavos et al. 2019aTsiavos et al. , 2019bTsiavos et al. , 2020a, geofoam (Murillo et al. 2009;Azinović et al. 2014;Azzam et al. 2018;Gatto et al. 2020;Gatto et al. 2021a;Gatto et al. 2021b;Gatto et al. 2022;Hadad et al. 2017;Karatzia et al. 2017;Koren and Kilar 2016;Xue et al. 2021), and some hybrid solutions (Ali et al. 2022;Tsiavos et al. 2020bTsiavos et al. , 2021aTsiavos et al. , 2021bYuan et al. 2021;). The base isolation concept was categorized by Tsang (2008) as a "Geotechnical Seismic Isolation (GSI) system" and also adopted by Brunet et al. (2016), Forcellini (2017), and Banović et al. (2019). ...
... Researchers have used various types of low-modulus material, such as sand (Anastasopoulos et al. 2012;Banović et al. 2018b;Patil et al. 2016;Radnić et al. 2015), sand-bitumen mixtures (Kuvat and Sadoglu 2020), gravel (Pecker 2003;Pecker et al. 2001;Steenfelt et al. 2015), stone pebbles (Banović et al. 2018a(Banović et al. , 2019(Banović et al. , 2020a(Banović et al. , 2020bBanović 2021), rubber-soil mixtures (Brunet et al. 2016;Forcellini 2017, Forcellini 2020Forcellini 2021;Hernández et al. 2020;Mavronicola et al. 2010;Pitilakis et al. 2021;Tsang 2008;Tsang 2009;Tsang et al. 2012;Tsang et al. 2020;Tsiavos et al. 2019aTsiavos et al. , 2019bTsiavos et al. , 2020a, geofoam (Murillo et al. 2009;Azinović et al. 2014;Azzam et al. 2018;Gatto et al. 2020;Gatto et al. 2021a;Gatto et al. 2021b;Gatto et al. 2022;Hadad et al. 2017;Karatzia et al. 2017;Koren and Kilar 2016;Xue et al. 2021), and some hybrid solutions (Ali et al. 2022;Tsiavos et al. 2020bTsiavos et al. , 2021aTsiavos et al. , 2021bYuan et al. 2021;). The base isolation concept was categorized by Tsang (2008) as a "Geotechnical Seismic Isolation (GSI) system" and also adopted by Brunet et al. (2016), Forcellini (2017), and Banović et al. (2019). The seismic isolation concept is based on the use of low-modulus materials surrounding the foundation of the structure for absorbing seismic energy and exerting a function similar to that of a cushion (Tsang 2008). ...
... The base isolation concept was categorized by Tsang (2008) as a "Geotechnical Seismic Isolation (GSI) system" and also adopted by Brunet et al. (2016), Forcellini (2017), and Banović et al. (2019). The seismic isolation concept is based on the use of low-modulus materials surrounding the foundation of the structure for absorbing seismic energy and exerting a function similar to that of a cushion (Tsang 2008). ...
Article
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This paper presents the findings of an experimental investigation of the efficiency of several low-cost frictional geotechnical seismic isolation methods on a rigid building model. A total of eleven different aseismic layers were considered. One layer was made of stone pebbles only, whereas the remaining ten layers were composites containing combinations of stone pebbles with different types and positions of “sliding” elements/materials (geogrid, geomembrane, and limestone sand layers). All the samples were exposed to four earthquake accelerograms of different durations and predominant periods, with three levels of peak ground acceleration (PGA): 0.2, 0.4, and 0.6 g. The test results confirm that the composite aseismic layers can significantly reduce the inertial/earthquake forces of the rigid building model relative to the stone pebble layer, depending on the type of earthquake and PGA. The need for further research on this issue on real building models is highlighted.
... Geotechnical seismic isolation (GSI) can be very promising and effective alternative isolation technique for low-to-medium rise buildings (Tsang, 2008;Tsang et. al., 2012;Goztepe, 2016). ...
... Because of the fact that isolator contact with entire foundation of the structure in the GSI system, the GSI system is defined as distributed seismic isolation system. Recent studies support the feasibility of the implementation of sand-rubber mixtures as an effective seismic isolation layer below a structure's foundation (Tsang 2008;Tsang et al., (2012);Pistolas 2015;Goztepe, 2016;Brunet et al. 2016). Tsang (2008) and Tsang et al., (2012) are the one of the most important research in this issue. ...
... Recent studies support the feasibility of the implementation of sand-rubber mixtures as an effective seismic isolation layer below a structure's foundation (Tsang 2008;Tsang et al., (2012);Pistolas 2015;Goztepe, 2016;Brunet et al. 2016). Tsang (2008) and Tsang et al., (2012) are the one of the most important research in this issue. They investigated geotechnical seismic isolation for low to medium rise building using granulated rubber soil mixtures by numerical studies. ...
Article
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Processed waste tires can be used as additives for geotechnical applications in earthquake-prone areas. The increasing use of waste tires additives requires a better understanding of their dynamic behaviors. Processed waste tires as granular and fiber-shaped rubber particles under the same experimental conditions were not studied before. The main purpose of this study is to carry out these experiments to determine the effects of two different processing techniques on the shear modulus and damping ratios of the mixtures. It is also the first time that the effects of fiber-shaped rubber particle inclusions are determined in detail.In addition, the results of similar tests using different processed waste tires were evaluated. The effects of the processed waste tires are given by evaluating the literature and this study together. It has been found that depending on the size, aspect ratio and content of the rubber material, the type of processing can significantly affect the dynamic properties of the mixture.The tested materials may be suitable as base isolation material. Of all the studies evaluated, the highest damping ratio was obtained with granulated rubber inclusions.
... These methods can be defined as GSI systems that facilitate dynamic soil-foundationstructure interaction based on flexible foundation materials. Tsang (2008) investigated numerically and showed the efficiency of the use of a 2m thick, flexible sand-rubber foundation layer for the seismic isolation of structures in developing countries. Tsang et al. (2021) and Tsiavos et al. (2019) investigated experimentally the seismic response of structures founded on a sand-rubber layer. ...
... Most of the existing highly engineered seismic isolation systems require the construction of two thick RC slabs above and below the seismic isolation system to enable its diaphragm function. However, most of the GSI methods (Tsang 2008, Gatto et al. 2020, Tsiavos et al. 2021a) require the construction of only one base slab at the foundation, thus decreasing the cost and the complexity of the existing seismic isolation methods. ...
... The systems that facilitate dynamic soil-foundation-structure interaction based on flexible foundation materials usually require a deep excavation below the structure, which can be designed to deamplify the seismic motion, thus protecting the superstructure from seismic damage. The efficiency of the method for the seismic isolation of high-rise slender buildings has been numerically demonstrated by Tsang (2008). This design proposal includes the use of this method for high-rise, slender buildings, as shown in Fig. 2. ...
... Considering the damping characteristics of rubber, researchers tried using shredded rubber in soil [5,6] for earthquake protection of buildings. Some researchers used tyre chips instead of pure rubber around the foundation [7][8][9] as seismic base isolation. They reported substantial response reduction in the structures and the foundations when subjected to earthquake excitation. ...
... They reported substantial response reduction in the structures and the foundations when subjected to earthquake excitation. The feasibility of using shredded rubber mixed with sand as a natural base isolator was investigated analytically by Tsang [7] and Nanda et al. [8]. The geotechnical and mechanical properties of soil mixed with tyre chips increase soil's flexibility and damping characteristics [10][11][12][13], reducing the earthquake energy transmission to the superstructure. ...
... But, the amount of shredded tyre will affect the bearing capacity of the WTSM layer. The optimum rubber-soil ratio that seems to effectively fulfil both bearing capacity and porosity criteria is 3:1 [7], in which rubber is 75% by volume. ...
Article
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Due to the rising amount of waste rubber products, there is an urge to recycle these products and reduce waste disposal. Crumb rubber tyre in the sand decreases pore water pressure, creating a good drainage path and reducing liquefaction in saturated dense sand. This paper investigates the effect of the waste tyre and soil mixture (WTSM) layer around the piles in mitigating earthquake-induced liquefaction through finite element analysis in OpenSees platform. The effectiveness of this technique in reducing pile response is investigated through a parametric study with varied depth and thickness of the WTSM layer. It is estimated that a reduction in pile response is achieved with an increase in WTSM volume. It is also estimated that placing the same volume of WTSM layer depth-wise gives better control. Finally, for closely spaced piles WTSM mat of 1–1.5 m depth is proposed for liquefaction-induced pile damage control for buildings. Huge stock of scrap tyres may be used for pile response reduction due to liquefaction as recycling of waste tyre.
... With the ideal isolation strategy in mind, it is sensible and logical to design a seismic isolation system that is based on filling the "levitated" gap with low-modulus materials (C1) (refer Fig. 1b). This is also the basic configuration of a GSI system as firstly proposed in Tsang (2008). It is well known that the hyperloop with an airless tube exhibits superior performance to the existing maglev train system. ...
... Considering the compatibility with the natural environment and the availability of materials, mixtures of soil and waste tyre rubber, also known as rubber-soil mixtures (RSM), have been proposed as a desirable choice for GSI (Tsang 2008). The potential of upcycling a huge amount of waste tyre rubber is an additional benefit (Tsang 2012). ...
Article
Full-text available
Geotechnical Seismic Isolation (GSI) can be defined as a new category of seismic isolation techniques that involve the dynamic interaction between the structural system and geo-materials. Whilst the mechanism of various GSI systems and their performance have already been demonstrated through different research methods, there is a missing link between fundamental research and engineering practice. This paper aims to initiate the development in this direction. A new suite of equivalent-linear foundation stiffness and damping models under the same framework is proposed for four GSI configurations, one of which is a novel combination of two existing ones. The exact solutions for the equivalent dynamic properties of flexible-base systems have also been derived that explicitly include the foundation inertia and the strain-dependent equivalent damping of foundation materials, which are both significant for GSI systems. The application of the proposed analytical design models has been illustrated through response history analyses and a detailed hand-calculation design procedure has also been outlined and demonstrated.
... In general, the TDA is chemically very stable with almost no ageing material. TDA has recently been deployed in variety of applications, including; (i) lightweight filling material [37][38][39] to isolate the vibration of foundations [40,41], (ii) buried pipelines, and (iii) retaining walls, etc. However, there is a problem with the possibility of TDA contaminating the groundwater. ...
... Although, the open trench tends to reduce the vibration by up to 80% (immediately behind the trench) in the TFVS scheme (L = 2.0), it must be noted that an increase of up to 40-50% vibration is recorded in front of the trench. It should also be noted that the magnification of the vibration in the trench front is observed in other studies by various researchers [14,31,41,45]. In the current study, the TDA barrier shows an effective vibration reduction effect, reducing vibration by up to 70%. ...
Article
Forging hammer machine foundation is subjected to multiple consecutive transient or impact loads during operation which results in a powerful dynamic effect. The dynamic effect may transmit to the surroundings in the form of unwanted vibration and could affect workers, other sensitive equipment in the same facility, and/or adjacent residential areas. Several studies in the past have used open and filled trenches to mitigate ground vibrations caused by harmonic loads. However, studies pertaining to precisely evaluate the vibration isolation performance of trenches in presence of transient loads are limited, and almost no attempt has been made to evaluate the use of tire-derived aggregates (TDA) and rubber-sand mixtures (RSM) as filling materials. This paper aims to investigate the potential of using the TDA and RSM barriers to reduce vibration caused by transient or pulse loads. Abaqus v6.14 software is used to perform two-dimensional (2D) finite element modelling for checking the efficiency of open and filled trenches. The model is first calibrated by comparing the results under harmonic loading conditions with the previous literature. The calibrated model is used further to evaluate different trench parameters, such as depth, width and distance from source to the barrier, upon shielding vibrations. Additionally, a multi-trench isolation system is simulated, and its performance is evaluated by comparing it with a single barrier. The results show that the TDA and RSM barriers effectively reduce the vibration induced by pulse loading. The difference in vibration screening efficiency between open and filled TDA trenches is about 10%. Moreover, the results indicate that multiple trenches are the preferred alternative because they attenuate vibration better than a single barrier.
... In general, the TDA is chemically very stable with almost no ageing material. TDA has recently been deployed in variety of applications, including; (i) lightweight filling material [37][38][39] to isolate the vibration of foundations [40,41], (ii) buried pipelines, and (iii) retaining walls, etc. However, there is a problem with the possibility of TDA contaminating the groundwater. ...
... Although, the open trench tends to reduce the vibration by up to 80% (immediately behind the trench) in the TFVS scheme (L = 2.0), it must be noted that an increase of up to 40-50% vibration is recorded in front of the trench. It should also be noted that the magnification of the vibration in the trench front is observed in other studies by various researchers [14,31,41,45]. In the current study, the TDA barrier shows an effective vibration reduction effect, reducing vibration by up to 70%. ...
Article
Forging hammer machine foundation is subjected to multiple consecutive transient or impact loads during operation which results in a powerful dynamic effect that transmits to the surroundings in the form of unwanted vibration thus affecting workers, other sensitive equipment, and/or adjacent residential areas. Previous studies incorporated open and filled trenches to mitigate the ground vibrations caused by harmonic loads. However, studies pertaining to precisely evaluate the vibration isolation performance of trenches in presence of transient loads are limited, and no attempt has been made to evaluate the use of tire-derived aggregates (TDA) and rubber-sand mixtures (RSM) as filling materials. This paper aims at investigating the potential of using the TDA and RSM barriers to reduce vibration caused by transient or pulse loads. Abaqus software was used to perform two-dimensional (2D) finite element modelling for checking the efficiency of open and filled trenches. The model was first calibrated by comparing the results under harmonic loading conditions with the previous literature. The calibrated model was further employed to evaluate different trench parameters, such as depth, width and distance from source to the barrier, upon shielding vibrations. Additionally, a multi-trench isolation system was simulated, and its performance was evaluated by comparing it with a single barrier. The results showed that the TDA and RSM barriers effectively reduces the vibration induced by pulse loading. The difference in vibration screening efficiency between open and filled TDA trenches was recorded as 10%. Moreover, the results indicated that the multiple trenches are preferred alternative owing to their capability of attenuating vibration more effectively in comparison to the single barrier.
... When a sliding interface is adopted, it is referred to as a sliding isolation system, this is an attractive and viable option for the seismic isolation of rural buildings because of its convenient construction and low cost. 17,18 If a sliding/flexible interface is placed underneath the foundations of a structure to isolate the superstructure and the foundation, it can be referred to as a foundation isolation system. 19 If the sliding/flexible interface is placed within the soil below the foundation of a structure to isolate the whole building and the soil, it is usually referred to as a geotechnical isolation system. ...
... In addition, the damping of the sand/gravel pad increases with increasing shear deformation. 15,17,28 The above-mentioned characteristics form the main isolation mechanism of the sand/gravel pad. ...
Article
Full-text available
This paper proposes a hybrid seismic isolation system composed of geotechnical (a layer of sand or gravel as foundation soil) and structural isolation (a low-friction foundation sliding layer), aiming to effectively improve the seismic performance of rural buildings with an economical solution. The isolation system is most suitable for low-rise buildings in high-seismic areas. It is also effective in colder climates as replacing sand or gravel as the foundation soil eliminates frost heave. Shake table testing of three 1/4 scale models of two-story masonry buildings was carried out: an unreinforced brick masonry structure (model MA, without isolation), an identical structure with geotechnical isolation (model MS, with a layer of gravel as the foundation soil), and an identical structure with hybrid geotechnical and structural isolation (model MC). The dynamic characteristics and responses of the three structures were assessed and compared. Test results showed that shear failure of brick walls of model MA occurred at the first story when the input peak ground acceleration reached 0.44g. For model MS, a similar shear failure mode occurred when the acceleration reached 1.02g. Model MC relied on the layer of gravel for isolation before 0.44g, and then several cracks occurred at the foundation sliding layer, which was a sign of sliding. The plastic damage was mainly concentrated in the second story, and model MC showed bending-dominated deformation when the acceleration increased to 1.24g. This study clearly demonstrates the improved seismic performance and technical feasibility of the cost-effective hybrid isolation system.
... 的思想也被应用于调控低频地震波的器件设计上。2018年,Pu 和Shi [41] 在层状土中以矩形晶格人为排布周期性桩基础,通过结构的瑞利波及勒夫波在低频范围内会有效衰 减。他们改变了柱间距,即晶格常数,发现整体结构的衰减域能够得到有效调控。但是,此调控方法在整体 结构设计施工完成之后就不能够灵活实施,属于被动调控范畴。为了应对不同的环境以及多变的实际需求, 半主动 [42,43] 或者主动 [44] 的方式也被应用到抗震结构上。 光子晶体、声子晶体中的结构形式、奇特性质不胜枚举,将它们应用于低频地震超材料的设计,可采用 的结构有拉胀超材料 [45] 、手性超材料 [46] 、负刚度超材料 [47] 等。由此可见,虽然光波与地震波有巨大区别,但 在地震超材料领域,通过合理利用纳米光子发展以来设计出的一些人工结构,可以有效且智能地调控低频地 震弹性波。 1.3 自然界的地震超材料 自然界的事物和规律等一直为研究者提供思路及理念,多应用于仿生结构的设计。例如,Neil等人 [48] 近 期发现,蛾翅是一种天然的声学超材料;Huang等人 [49] 受蛾眼启发,设计出一种可调频且具有疏水性的电磁 波超材料。类似地,Colombi等人 [50] 将超材料中的局域共振机理和自然界的树木联系在一起。他们发现,当 瑞利波通过森林时,在半波长范围内周期排列的树木将会发生低频共振,这个行为和局域共振型声学超材料 非常相似。尽管该研究的激发频率小于150 Hz,但是他们指出,竖直共振单元的共振频率与其长度成反比, 故可据此设计出共振频率小于10 Hz的结构,以应用于实际的地震瑞利波衰减调控。这个发现引发了人们探 求森林超材料(forest seismic metamaterial)这种天然地震超材料的兴趣。 此后,Lata等人 [51] 利用地震波在空间排布树木中散射的几何相位研发出一种声学传感(acoustic sensing) 技术,可以实现远距离监测。Liu等人 [52] 研究了城市森林地震超材料的减震效能,并分析了土壤的弹性模量 等因素对于禁带的影响。Muhammad等人 [53] 研究了瑞利波在森林地震超材料的研究情况,考察了树木的机械 及几何特性等因素对整体系统效能的影响。他们发现,当树木的纵向共振模式与在软沉积土中传播的瑞利波 的垂直分量相互耦合时,能够观测到非常强的波衰减。因此,森林中的树木可以精确地用作天然的局域共振 超材料,能够通过结构优化在低频范围内产生极宽带隙 [53] 。但是,这些工作一般将树木简化成竖直柱形局域 共振单元,未考虑实际中树木本身的性质,例如树枝甚至树叶对整体系统的影响。因此,Muhammad和Lim [54] 在2021年把研究聚焦在树枝的分布对于森林超材料的影响,如图3所示。通过测试频率响应,他们发现,这 样的结构能产生在20 Hz左右的低频宽禁带。并且,他们还考察了单侧树枝和两侧树枝的影响。他们还进一 步基于不同频率下整体系统的位移场分布,发现了一部分瑞利波会被树木俘获而另一部分瑞利波则被转化为 剪切体波传向深处地层。 图 3 (网络版彩色)一种周期性森林超材料 [54] . 2.1 外部屏障型地震超材料 在垂直位置上,外部屏障型地震超材料又可细分为地表面上和地下的人工结构,前者的设计机理类似于 森林超材料。2016年,Colombi等人 [55] 研究了一种位于地表外部的地震波屏障,在此结构中,局域共振单元 的高度从左到右依次增加,如图4所示。他们 [56] 首先研究了低频瑞利波从较低共振单元入射,得到了类似声 子中的"彩虹俘获"现象,他们把此现象称为"地震彩虹"(seismic rainbow)。不同的是,当瑞利波从较高共 振单元入射时,表面瑞利波会转化为剪切波。Kacin等人 [57] 提出了一种圆孔型三角形阵列组成的地震超材料, 该结构在25~36 Hz周围有两个低频禁带,并能够将它们降低到8 Hz,对衰减表面波非常有效。Xu等人 [58] 通过 在空心圆柱体内引入一种加号形状的结构,改进了普通空心圆柱体结构的地震超材料。研究表明,这样的新 型结构能产生3倍于普通结构的低频禁带。Hajjaj和Tu [59] 则将目光转向新型材料:贫铀(depleted uranium)。贫 铀具有高密度、高熔点、较高的拉伸强度、价格低等特点。通过将贫铀制成内部质量块加入钢制圆柱壳中, 能够减小相似系统中共振单元的尺寸而不影响其产生低频带隙,这个发现为利用工业废料制造地震超材料提 供了理论与实践依据。 2017年,Colquitt等人 [60] 类比光学中的超表面,提出了地震超表面(seismic metasurface)的概念。他们研究 了一组在薄弹性板或者弹性半空间上周期分布的杆状局域共振单元,发现在这两种情况下,由于禁带的存在, 表面的瑞利波和局域共振单元作用,转化为体波。之后,Wootton等人 [61] 、Pu等人 [62] 、Liu等人 [63] 、Palermo 等人 [64] 都借鉴了这个概念,设计出新型的结构来调控地震表面波。总之,这些位于地表外部的屏障型地震超 材料的优势在于不受深层地质结构的影响,仅受浅表层地面的约束,设计施工简单。但是,其也有一定的缺 陷,例如,在密集建筑群中会受实际城市规划的限制。 图 4 (网络版彩色)一种位于地表外部的屏障型地震超材料 [55] . ...
... Furthermore, seismically isolated structures can manifest inelastic behavior even for ground motion intensities corresponding to the design hazard level, when they are unintentionally constructed with lower strength than the value prescribed by the code provisions [4][5][6][7]. The investigation of such behavior of existing seismically isolated structures sheds light on their reliability and robustness compared to fixed-based structures, as defined by Castaldo et al. [8,9], Tsang [10] and Peng et al. [11]. ...
Conference Paper
Full-text available
The goal of this study is to determine experimentally the inelastic response modes of seismically isolated structures. A steel specimen is designed and constructed to simulate the dynamic behavior of a Single-Degree-Of-Freedom (SDOF) system. The specimen is seismically isolated with four friction pendulum bearings and excited by a group of earthquake ground motion records using the shaking table of ETH Zurich Laboratory. A mechanical clev-is connection consisting of two hinges and two replaceable steel coupons is designed and constructed to facilitate the parametric investigation of the inelastic response of the isolated structure for varying values of its strength. Two fundamentally different inelastic response modes have been observed during the excitation of the structure: A response mode dominated by large sliding displacement demand in the isolators and a response mode characterized by large displacement ductility demand in the isolated structure. This paper shows the effect of the design parameters of the isolation system and the isolated structure on the manifestation of these two response modes, thus paving the way for the understanding of the inelastic response of seismically isolated structures subjected to extreme earthquake ground motions.
... Tire derivatives are also proposed as a soil reinforcement by many researchers [11,12]. It also possesses high vibration reduction capacity [13,14], and tire derivatives are reported to improve sands resistance towards liquefaction [15]. ...
Article
Disposal of the scrap tire is of great concern in many countries across the globe. Several studies have been reported in the past for effective reuse of these scrap tires. The use of scrap tire derivatives in civil engineering application is also an emerging field in the recent years. In this study, an experimental testing program was carried out to investigate the behaviour of tire chip, sand and sand–tire chips mix. The study reports the effect of tire chips inclusion on the sand properties. The materials were investigated for different characteristics like specific gravity, void ratio, water absorption, compressibility and shear behaviour. Along with the mixes, behaviour of a single tire chip was also investigated. The tire chips were reported to be highly compressible in nature and possess very low shear strength in comparison to sand. The addition of tire chips to the sand resulted in the decrease in the shear strength and increase in the compressibility of the mix. High plastic strains are also observed for mixes with tire chips content. An optimum sand–tire chips mix is also suggested based on the results of the present study.
... It is one of the main ways to recycle waste tyres by crushing them into rubber particles and then used in civil engineering. Mixtures of small-sized rubber and sand have important applications in geotechnical engineering [3,4], and a study has shown that rubber sand is a suitable and cheap damping material: Tsang [5] studied using rubber sand to replace foundation soil; when the maximum dynamic shear modulus of rubber sand cushion is 7.5 MPa and the thickness is 10 m, the peak value of horizontal acceleration of superstructure is 75% lower than that before replacement, and the peak value of vertical acceleration is 90% lower than that before replacement; Panah and Khoshay [6] filled the rubber sand into the pipe pile, and the lateral static load test, free vibration test, and forced vibration test are carried out, respectively. e test results show that the pipe pile has good deformation ability and damping characteristics. ...
Article
Full-text available
Up to now, there are few reports on the application of microbial-induced calcium carbonate precipitation (MICP) consolidated rubber sand. By means of uniaxial or cyclic loading test and SEM test, the consolidation effect of rubber sand samples with different rubber particle content after MICP consolidation is tested and analyzed. The results show that MICP is not affected by the amount of rubber particles; rubber particles improve the compressive strength and deformation ability of consolidated rubber sand samples and significantly enhance the damping ratio, resistance to deformation, and energy dissipation ability of consolidated rubber sand samples. Rubber sand after MICP consolidation is a good shock damping material. The conclusion of this paper provides reference data for the application of microbial-induced calcium carbonate precipitation consolidated rubber sand.
... Recycled rubber is an elastomer type of polymer with very low specific gravity and high energy dissipation properties; thus, it has very attractive properties to be used in a variety of applications such as lightweight geosynthetic, alternative and low-cost vibration isolation earth material, or drainage earthen system in landfills [1][2][3][4][5][6][7][8][9][10]. Many research studies have proposed the use of recycled rubber in granulated/shredded form in various projects, for example, as lightweight embankment/subgrade material [11][12][13][14][15][16], backfill in retaining walls [12,[17][18][19][20], high damping capacity system beneath foundations [21][22][23][24], isolation material mitigating soil liquefaction [25][26][27][28], and railway ballast [29]. Recycled rubber, apart from being used in geotechnical engineering as a lightweight material, also finds a variety of other potential applications such as composite material in new concrete production or asphalts [30][31][32], and it may find applications in industrial and aeronautic engineering as well [33][34][35]. ...
Article
Full-text available
Recycled rubber in granulated form is a promising geosynthetic material to be used in geotechnical/geo-environmental engineering and infrastructure projects, and it is typically mixed with natural soils/aggregates. However, the complex interactions of grains between geological materials (considered as rigid bodies) and granulated rubber (considered as soft bodies) have not been investigated systematically. These interactions are expected to have a significant influence on the bulk strength, deformation characteristics, and stiffness of binary materials. In the present study, micromechanical-based experiments are performed applying cyclic loading tests investigating the normal contact behavior of rigid–soft interfaces. Three different geological materials were used as “rigid” grains, which have different origins and surface textures. Granulated rubber was used as a “soft” grain simulant; this material has viscoelastic behavior and consists of waste automobile tires. Ten cycles of loading–unloading were applied without and with preloading (i.e., applying a greater normal load in the first cycle compared with the consecutive cycles). The data analysis showed that the composite sand–rubber interfaces had significantly reduced plastic displacements, and their behavior was more homogenized compared with that of the pure sand grain contacts. For pure sand grain contacts, their behavior was heavily dependent on the surface roughness and the presence of natural coating, leading, especially for weathered grains, to very high plastic energy fractions and significant plastic displacements. The behavior of the rigid–soft interfaces was dominated by the rubber grain, and the results showed significant differences in terms of elastic and plastic fractions of displacement and dissipated energy compared with those of rigid interfaces. Additional analysis was performed quantifying the normal contact stiffness, and the Hertz model was implemented in some of the rigid and rigid–soft interfaces.
... In between, and even if they are very common materials, systems composed of grain with very different -soft and hard -rheologies, driven far above the jamming transition, have a bewildering but fascinating behavior that stays mostly misunderstood. They have been experimentally studied in very specific applications like for stress releasing [24,25], seismic isolation [26,27] or foundation damping [28,29]. However, to our best knowledge, no local measurements have been performed to understand micro-processes leading to their very specific macroscopic behavior. ...
Preprint
Full-text available
In this letter, we report on an experimental study which analyzes the compressive behavior of 2D bidisperse granular assemblies made of soft (hyperelastic) and hard grains in varying proportions ($\kappa$). By means of a recently developed uniaxial compression set-up \cite{vu2019_pre} and using advanced Digital Image Correlation (DIC) method, we follow, beyond the jamming point, the evolution of the main mechanical observables, from the global scale down to the strain field inside each deformable grain. First, we experimentally validate and extend to the uni-axial case a recently proposed micro-mechanical compaction model linking the evolution of the applied pressure $P$ to the packing fraction $\phi$ \cite{cantor2020_prl}. Second, we reveal two different linear regimes depending on whether the system is above or below a cross-over strain unraveling a transition from a discrete to a continuous-like system. Third, the evolution of these linear laws are found to vary linearly with $\kappa$, up to a saturation point around $\kappa=80$\% of hard particles. These results provide a comprehensive experimental and theoretical framework that can now be extended to a more general class of polydisperse soft granular systems.
... Recently, Vu et al. [20,79,80] presented experimental and numerical studies on twodimensional rubber-like particles. They find that first, the hyperelastic behavior driven by the neo-Hookean model [81], new properties such as better stress relaxation [42,43,83], seismic isolation [45,46,84] and foundation damping [42,43,47] while reducing the weight and keeping the strength of the structures. ...
Thesis
La compaction d'assemblages de grains mous au-delà de leur point de blocage (i.e., le ``jamming point''), bien que très étudiée reste encore mal comprise. Par exemple, un très grand nombre d'équations reliant l'évolution de la pression de confinement $P$ à la compacité $phi$ ont été proposés mais la plupart des équations existantes s'appuient sur des stratégies empiriques impliquant souvent plusieurs paramètres d'ajustement dont le sens physique n'est pas toujours clair. Dans ce travail de thèse, au moyen de simulations numériques et d'expériences modèles, nous analysons la compaction de grains frottant hautement déformables, de différentes formes, ou encore des mélanges de grains déformable/rigide en deux et trois dimensions. Numériquement, nous utilisons la méthode de dynamique des contacts non régulière (``Non-Smooth Contact Dynamics NSCD'') couplant la méthode de Dynamique des Contacts (pour gérer le contact entre grains) à la méthode des Eléments Finis (pour la déformation des grains), et expérimentalement nous utilisons des techniques d'imagerie à haute résolution couplées à des algorithmes de DIC sur un système quasi-2D de compression unixial. Dans tous nos essais, nous caractérisons l'évolution de la compacité, du module élastique et de la microstructure (réarrangement des particules, connectivité, forces de contact et distributions des contraintes dans les particules) en fonction des contraintes appliquées. Nous montrons que la compacité évolue de manière non linéaire à partir du point de blocage et tend asymptotiquement vers une compacité maximale qui dépend du rapport de mélange de grains déformable/rigide, du coefficient de frottement ou encore de la forme des particules. À l'échelle microscopique, différentes relations en lois de puissances sont mises en évidence entre, d'un coté, les structures locales à l'échelle des grains et des contacts et, de l'autre coté, la compacité et la pression, indépendamment de la forme, du rapport de mélange ou de la dimension du problème (2D/3D). Finalement, un résultat majeur de ce travail est la mise en place d'un cadre théorique et micromécanique pour l'étude de la compaction d'assemblages granulaires mous au-delà du point de blocage. Ce cadre micromecanique s'appuie sur le tenseur des contraintes granulaires, sa limite aux petites déformations, et de l'évolution de la connectivité des particules. À partir de l'expression de ces quantités, nous établissons différentes équations de compaction, libres de tout paramètres {it ad hoc}, et reproduisant parfaitement nos données numériques et expérimentales. Ces équations dépendent principalement de la dimension considérée (2D/3D), et prennent en compte les caractéristiques de forme, de bi-dispersité élastique, ou de géométrie de compression (uniaxiale {it vs} isotrope). Le cadre micromécanique proposé permet d'unifier le comportement de compactage des assemblages de particules molles, molles/rigides et non circulaires de manière cohérente, à la fois en 2D et en 3D, pour une compression isotrope et uniaxiale.
... The fascinating mechanical and dynamical properties of rubber (i.e., low density, intense strength, electrical conductivity properties, durability and high damping and friction properties), makes this material -even the waste type-interesting to be used in geotechnical engineering. Many studies [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] have been investigated the mechanical and dynamical properties of rubber in company with soil (mixture, reinforced or even as part of the supper structure). Rubbers in many shapes (grained, shred, powder, sheet and even intact tire) have been used in many field projects, including the lightweight backfilling for retaining walls and highway engineering applications [17]. ...
Article
Full-text available
Nowadays the waste rubber problems are concerned due to the environmental issues, storage, and recycling difficulty. However, the rubber base equipment has been widely used to protect structures for vibrations - that has been generated by the structure or induced from the vicinity area or the bedrock into the structure - due to the notable capability of absorbing energy. In this study, the repeated-loading behaviour of the Sand Rubber Mixture (SRM) has been investigated and the remarkable energy absorption properties of the mixture have been illustrated. The test soil material that has been used in this study was a well-graded sand (SW) with a mean grain size of 2 mm. The test martial rubber that has been used was grain particles with a uniform size of 4.76 mm. The sand rubber mixture (SRM) was prepared by using 7.5% rubber inclusion because it was found as the optimum rubber content. A series of force control repeated-loading CBR tests have been arranged. The effect of mixing rubber particles with the well-graded sand (SW test material) has been investigated. This shows the remarkable energy absorption capability of Sand Rubber Mixture (SRM) to protect the bed of a machine’s footing that is generating repeated loads. The SRM usage could be extended to be employed as a part of an energy absorption unit and dampers facilities beneath a machine footing or structures that are sensitive to the vibration to prevent destructive deformation and resonance phenomenon.
... The rubber has been used as a part of many dampers and energy dissipater equipment. Remarkable energy dissipation properties of the rubber and its application in geotechnical and earthquake engineering has been assessed by many researchers in many forms of sheets, grains, shredded etc. [13,[23][24][25][26][27][28][29][30]. As the rubber has much smaller stiffness in comparison to the soil and considering its notable damping properties, it could be an ideal material to be used as a method to improve the dynamic response of machine foundations. ...
Article
Full-text available
Placing a machine footing over a small thickness of soil layer, which is located over a bedrock, could encounter many challenges due to the bed’s notable stiffness in comparison to the soil. The advantages of using rubbers to protect facilities (structures, machine foundations, nearby footings and equipment, etc.) from vibration and control its consequences are well known nowadays. In this study, the benefits of employing a small thickness of rubber sheet (2 mm) on the dynamic response of a machine foundation which is located over four thicknesses of soil (210, 420, 630, and 840 mm) has been investigated. The soil layer is located over an artificial bedrock that is consisted of a thick concrete layer. The tests have been conducted in a vast test pit of size 2500×2500 mm and a depth of 840 mm by using a semi large-scale machine foundation model with a square concrete foundation of width 400×400×100 mm. It was observed that, by increasing the soil layer thickness, the resonant frequency and amplitude of the vibrating system decreases. Moreover, by employing a rubber sheet beneath the machine footing, the resonant frequency of the vibrating system significantly decreases especially for a small thickness of the soil layer. Although, using a rubber sheet could slightly increase the resonant amplitude, but the benefit of the resonant frequency-changing capability of the rubber sheet is too impressive by taking the resonant frequency of the system far enough from the unchangeable working frequency of the machine and preventing the resonant phenomenon to happen.
... However, both the burning and production of the rubber powder are not environmentally friendly and usually require extra energy to clean. More recently, the reuse of waste tires in the form of tire shreds and granulated rubber as new geo-materials or in the form of mixtures with soil has become a popular approach in the construction of civil engineering structures, such as lightweight embankment fill [3,4], lightweight retaining wall backfill [5,6], drainage layers for roads, landfills, and other applications [7][8][9], thermal insulation to limit frost penetration beneath roads, insulating backfill to limit heat loss from buildings and vibration damping layers for rail lines [10][11][12][13][14][15], which have great potential to alleviate the waste tire accumulation problems and are considered environmentally friendly methods [16]. ...
Article
Full-text available
Mixing soil with waste tire rubber granules or fibres is a practical and promising solution to the problem of global scrap tire pollution. Before successful applications, the mechanical behaviour of the soil–rubber mixture must be thoroughly investigated. Comprehensive laboratory studies (compaction, permeability, oedometer and triaxial tests) were conducted on the completely decomposed granite (CDG)–rubber mixtures, considering the effects of rubber type (rubber granules GR1 and rubber fibre FR2) and rubber content (0–30%). Results show that, for the CDG–rubber mixture, as the rubber content increases, the compaction curves become more rubber-like with less obvious optimum moisture content. The effect on permeability becomes clearer only when the rubber content is greater than 30%. The shape effect of rubber particles in compression is minimal. In triaxial shearing, the inclusion of rubber particles tends to reduce the stiffness of the mixtures. After adding GR1, the peak stress decreases with the increasing rubber content due to the participation of soft rubber particles in the force transmission, while the FR2 results in higher peak stress especially at higher rubber contents because of the reinforcement effect. For the CDG–GR1 mixture, the friction angle at the critical state (φ’cs) decreases with the increasing rubber content, mainly due to the lower inter-particle friction of the CDG–rubber interface compared to the pure CDG interface, while for the CDG–FR2 mixture, the φ’cs increases with the increasing rubber content, again mainly due to the reinforcement effect.
... Thus, on a practical standpoint, ground treatment with rubber may provide beneficial solutions in improving the performance of engineered soils. Because of their high energy dissipation capacity, rubber has also been proposed and examined through laboratory research works and theoretical studies to be used as an alternative and of low-cost seismic isolation measure for superstructures and earth systems [28,65]. ...
Article
Full-text available
The contact problem of soft-rigid interfaces is investigated in this study performing micromechanical-based experiments on sand (rigid) grains sliding against granulated (soft) rubber and by incorporating the Mindlin-Deresiewicz model. The analysis suggested that modifications of the theoretical model are necessary by taking into account, quantitatively, the deformable nature of the soft particles in terms of self-deformations during sliding. Interface friction, tangential stiffness and microslip displacement are analyzed and an attempt is made to provide inter-correlations among different contact parameters, incorporating experimental stiffness and realistic displacement thresholds into the theoretical model. Graphic abstract
... Moreover, the use of tire shreds was proposed in the design of embankments overlying soft soils to minimize the vertical stresses and settlements 24,28 and have been investigated experimentally in constructing a drainage layer based on their high hydraulic conductibility. 29,30 SRM suitability and advantages as GSI in the form of a layer underlying the foundation of a structure have been investigated numerically by many researchers, 13,[31][32][33][34][35][36][37][38] demonstrating the decrease of the foundation's horizontal and vertical motions. Additionally, it was stated that the low modulus of the SRM foundation layer contributes to the reduction of the rocking stiffness of the structures. ...
Article
We present the results of a large‐scale experimental campaign performed on the prototype structure of EuroProteas in Thessaloniki, Greece, to assess the effectiveness of gravel‐rubber mixture (GRM) layers underneath shallow foundations as a means of geotechnical seismic isolation (GSI). We found that the GSI of structures is optimized by increasing the rubber content of the soil‐rubber mixture up to 30% per mixture weight. The effectiveness of the GSI systems has been investigated numerically and in small‐scale experiments. This article seeks to fill the gap in the lack of full‐scale experimental studies on this subject. Three soil pits were excavated and backfilled with GRM of different rubber content per weight to serve as foundation soil. A large number of instruments were installed on the structure, the foundation, the soil surface, and inside the GRM layers beneath the foundation to fully monitor the GSI‐structure systems’ response in three dimensions. The experimental investigation included ambient noise, free‐ and forced‐vibration tests. Our results showed that a GSI layer composed of a GRM with 30% rubber content effectively isolates the structure. Even 0.5 m thickness (ie, B/6 of the foundation width) of the GSI system successfully cuts off practically all emitted waves at a (horizontal or vertical) distance of B/6 from the foundation. A significant reduction in the GSI‐structure system's stiffness was apparent, leading to a rocking‐dominant response. The rise in the system's damping and the substantial energy dissipation inside the GRM layer highlight its effectiveness as a GSI system.
... The isolation mechanism is built upon various specialised areas in earthquake engineering, namely, non-linear material properties, dynamic soil-foundation-structure interaction, seismic wave propagation, rocking isolation and the traditional seismic isolation technique. Different kinds of materials can also be explored, which include geofoam (Karatzia and Mylonakis 2017;Xue et al. 2021), mixtures of soil and waste tyre rubber granules (Tsang 2008), ductile nylon fibres (Shimamura 2012), geotextiles (Dhanya et al. 2020), polyurethane (Gatto et al. 2021), super absorbent polymers (SAP) (Nappa et al. 2016) and metamaterial (Cheng et al. 2020). GSI research also covers sustainability and environmental impact assessment, e.g. ...
Conference Paper
Full-text available
Geotechnical Seismic Isolation (GSI) is an emerging category of earthquake protection systems that involve dynamic interaction between the structure and geomaterials. This new field of study has diversified and gained momentum through a decade of research. This paper attempts to consolidate the collective research efforts at a high level and put forward a vision plan for global collaboration amongst GSI researchers and for multi-sectoral engagement with end-users including governments, non-governmental organisations, builders, engineering professionals and local communities. Finally, resilience, sustainability and universality, as the three overarching goals of GSI, are highlighted.
... Thus, a need still exists for new recycling solutions. Several possibilities consist of using shredded tires (usually referred as "tire chips") mixed with sand, as alternative soils which can be used in various geotechnical applications such as backfilling for retaining structures, slope and highway embankment stabilization, road constructions, soil erosion prevention and seismic isolation of foundations [2,[4][5][6]9,11,16,19,26,28]. ...
Article
Mixtures of rigid sand particles and soft rubber particles (rubber chips) are prepared and submitted to vertical taps in a confined cell to investigate their propensity to segregate. The mixture evolution is characterized by means of image analysis of slices obtained by a gelification technique. We show that, in case of equally sized particles, the rubber particles tend to migrate towards the bottom of the system. Yet, the segregation is not complete and is reduced when the rubber fraction is increased. Also it competes with the size induced segregation if rubber chips are larger than sand particles. A tendency to form horizontal clusters is clearly observed and increases with the number of taps. This horizontal segregation is reduced if the rubber fraction is smaller and is weakly influenced by grain size difference. Both the vertical segregation and the formation of horizontal heterogeneities are prevented by adding a small amount of water.
... Tsang et al. (2012Tsang et al. ( , 2008 proposed the use of locally available materials for seismic176 isolation. They concluded that if a mixture of rubber and sand is used beneath the foundation,177 it would not only reduce the vertical acceleration response but would also reduce the 178 horizontal vibrations. ...
Preprint
Full-text available
Masonry structures are frequently constructed in developing countries because of their affordability and ease of construction, despite the fact that they are vulnerable and perform poorly during earthquakes. Experimental and numerical studies were carried out to determine the optimum thickness of the isolation layer for a recently developed, low-cost seismic isolation system known as the Reinforced-Cut-Wall(RCW). The parameters of the isolation layer were optimized during the experimental and numerical investigation using hollow concrete blocks. Quasi-static cyclic tests were performed on 1:3 reduced-scale brick masonry wall, incorporating the RCW isolation scheme, validating the better performance of the proposed isolation technique.
... Namely, the dissipation of earthquake energy and the reduction of earthquake forces on the building in this concept are dominated by the sliding mechanism of the foundation on seismic isolation and between pebbles sublayers. Another way to describe mechanism of this isolation concept is the "distributed seismic isolation system," which has been discussed by Tsang [31] and Mavronicola et al. [32]. ...
Thesis
The problem under consideration is the earthquake impact on structures. The subject of the performed research is the efficiency of seismic base isolation using layers of predominantly natural materials below the foundation, as well as the development of a numerical model for seismic analysis of structures with such isolation. The aseismic layers below foundation are made of limestone sand - ASL-1, stone pebbles - ASL-2, and stone pebbles combined with layers of geogrid and geomembrane - ASL-3. The experimental research methodology is based on the use of shake-table and other modern equipment for dynamic and static testing of structures. Experiments were conducted on the basis of detailed research plan and program. Efficiency of the limestone sand layer - ASL-1 was tested on cantilever concrete columns, under seismic excitations up to failure, varying the sand thickness and intensity of seismic excitation. Influence of several layer parameters on the efficiency of stone pebble layer - ASL-2 was investigated. For each considered layer parameter, a rigid model M0 was exposed to four different accelerograms, with three levels of peak ground acceleration (0.2 g, 0.4 g and 0.6 g), while all other layer parameters were kept constant. On the basis of test results, the optimal pebble layer was adopted. Afterwards, the optimal ASL-2 efficiency was tested on various model parameters: stiffness (deformable models M1-M4), foundation size (small and large), excitation type (four earthquake accelerograms), and stress level in the model (elastic and up to failure). In the ASL-3 composite aseismic layer, the optimal ASL-2 is combined with a thin additional layer of sliding material (geogrid, geomembrane above limestone sand layer), in order to achieve greater efficiency of this layer than that of the ASL-2. A total of eleven different aseismic layers were considered. To determine the optimal ASL-3, the M0 model was used, like for the ASL-2. On the basis of test results, the optimal ASL-3 layer was adopted (one higher strength geogrid at the pebble layer top). The optimal ASL-3 is tested on various model parameters, analogous to the optimal ASL-2. A numerical model for reliable seismic analysis of concrete, steel, and masonry structures with seismic base isolation using ASL-2 was developed, with innovative constitutive model for seismic isolation. The model can simulate the main nonlinear effects of mentioned materials, and was verified on performed experimental tests. In relation to the rigid base - RB without seismic isolation, model based on the ASL-1 had an average reduction in seismic force and strain/stress by approximately 10% at lower PGA levels and approximately 14% at model failure. Due to the effect of sand calcification over time, the long-term seismic efficiency of such a layer is questionable. It was concluded that the aseismic layers ASL-2 and ASL-3 are not suitable for models of medium-stiff structure M3 and soft structure M4. In relation to the RB without seismic isolation, the M1 (very stiff structure) and M2 (stiff structure) based on the ASL-2 had an average reduction in seismic force and strain/stress by approximately 13% at lower PGA levels and approximately 25% at model failure. In relation to the RB without seismic isolation, the M1 and M2 based on the ASL-3 had an average reduction in seismic force and strain/stress by approximately 25% at lower PGA levels and approximately 34% at model failure. In relation to the RB without seismic isolation, the ASL-2 and ASL-3 did not result in major M1 and M2 model displacements, which was also favourable. It is concluded that the ASL-2 and especially ASL-3 have great potential for seismic base isolation of very stiff and stiff structures, as well as small bridges based on solid ground, but further research is needed. In addition, it was concluded that the developed numerical model has great potential for practical application. Finally, further verification of the created numerical model on the results of other experimental tests is needed, but also improvement of the developed constitutive models
... This is because the inclusion of these synthetic materials provides a means of ground improvement while reducing the overall weight of fills/backfills (Foose et al. 1996;Bernal et al. 1997;Youwai and Bergado 2003;Zornberg et al. 2004;Deng and Xiao 2010;Yi et al. 2015;Jamshidi Chenari et al. 2016, 2019Li et al. 2019a, b;Tizpa et al. 2019). Examples of these applications may refer to retaining walls (Humphrey and Sandford 1993;Lee et al. 1999;Lee and Roh 2007), lightweight embankments in transportation projects (Humphrey and Sandford 1993;Bosscher et al. 1992Bosscher et al. , 1997Dickson et al. 2001), as well as applications where vibration mitigation is targeted (Tsang 2008;Tsiavos et al. 2019;Alaie et al. 2021). This is because recycled rubber and EPS have enhanced dynamic properties such as high attenuation capacity; thus, they comprise an attractive and low-cost alternative to reduce seismic and other vibrationsource loads (Feng and Sutter 2000;Anastasiadis et al. 2012a;Senetakis et al. 2012;Ehsani et al. 2015;El-Sherbiny et al. 2018;Gao et al. 2019). ...
Article
Even though the mechanical behavior of granular soil-rubber mixtures has attracted significant attention and promising applications in geotechnical engineering, less attention has been paid to the influence of creep and long-term response of these composites. The present study examined the compression behavior of two types of sands mixed with recycled granulated rubber with emphasis on the influence of rubber percentage and sand grain type, providing in this way some new insights with emphasis on creep influences. One natural material is composed of Leighton Buzzard quartz sand of noncrushable grains, and the second material is composed of completely decomposed granite of crushable grains (note that the terms crushable and noncrushable refer to the range of maximum overburden pressures applied in the study that ranged from 0.3 to 6.7 MPa). The influence of creep on the compression behavior of the samples was associated with the location (or not) of the pure sand and their mixtures on the normal compression line (NCL) when creep deformations were evaluated. In specific, the rate of creep deformation was found to be independent of the stress level as long as the sample had reached its NCL during compression. Even though for LBS-rubber, there was a clear decrease of the stiffness of the mixtures expressed with the constrained modulus, this was not the case for the CDG-rubber mixtures, and within the scatter of the data, the ratio of creep index to compression index fell in a relatively narrow range (0.005-0.05), suggesting that the creep deformations could be predicted based on conventional oedometer tests with short-term measurements of the applied normal stress.
... Even more recent is the direct intervention in the soil, defined by Tsang (2008) and Tsang et al. (2012) as geotechnical seismic isolation (GSI), which is receiving growing interest. These techniques can be used to reduce earthquake-induced loads acting on superstructures, allowing to protect them from the potential effects of earthquakes. ...
Article
Full-text available
The paper focuses on the detailed analysis of the dynamic characterisation of polyurethane to evaluate the effects of polyurethane injections into soil with the aim of geotechnical seismic isolation. To determine the dynamic properties, resonant column (RC) tests were performed at the University Kore of Enna (Italy) on specimens of pure polyurethane with different values of density and subjected to different mean confining pressures. The results obtained by means of RC tests, in terms of shear modulus G and the damping ratio D as a function of shear strain γ c , allowed to develop an analytical formulation for G-γ c and D-γ c curves, taking into account the linear relationship with density, of both the maximum value of shear modulus G max and the minimum value of damping ratio D min . The analytical formulation derived from the experimental results is applied for ground response seismic analyses of cohesive soils injected with polyurethane, using a finite element code. The numerical results show that the polyurethane injections reduce the value of maximum acceleration on the ground surface and the reduction varies with the thickness of the soil modified by polyurethane injections.
... In addition to the advantages of environmental protection and control of expansion deformation, it also has a good damping capacity. Waste tire rubber is crucial to structures subjected to dynamic loads, such as building cushions requiring vibration isolation [26]. Damping ratio λ and dynamic shear modulus G are two of the most commonly used dynamic parameters in the study of dynamic properties of soft soils and have been extensively discussed for their ability to reflect the response of geotechnical materials to dynamic loads [27][28][29]. ...
Article
Full-text available
Using tire waste rubber reinforced expansive soil (ESR) can modify its poor engineering characteristics. The damping properties of ESR at different temperatures may vary dramatically. Two kinds of rubber Ra (large particle size) and Rb (small particle size) are mixed with expansive soil according to gradient ratio. The backbone curves, dynamic shear modulus, and damping ratio of expansive soil in varying temperature fields of 20 °C, −5 °C, and −15 °C are investigated. The Hardin-Drnevich model can well fit the backbone curves of ESR specimens in various temperature fields. Dynamic triaxial results show that 5–10% Ra rubber can withstand higher shear stress in all temperature fields; Rb rubber can increase the dynamic shear modulus of expansive soil and reach the peak value with 10% rubber content. The damping ratio can be significantly improved by using 10% Ra rubber at room temperature, while the ESR damping ratio in a temperature field of −5 °C does not change significantly with increasing shear strain or even decreases; Ra increases the damping ratio of expansive soils in the temperature field of 15 °C while small particle size Rb decreases the damping ratio of expansive soils. The experimental results validate the effectiveness of ESR in the frozen soil area. In an engineering sense, local temperature needs to be considered to use an appropriate ESR, which can provide effective seismic isolation and damping.
... Alternatively, Geotechnical Seismic Isolation (GSI) systems seek to modify the soil by means of introducing flexible or sliding interfaces directly in contact with geological sediments, e.g. geosynthetic liners and wave barriers (Tsang, 2008). Within this field, Rubber-soil mixtures (RSm) have been recommended to mitigate the action of seismic motions due to its low stiffness and relatively high damping capacity (Tsang et al., 2020;Tsang and Pitilakis, 2019;Hazarika et al., 2008). ...
Conference Paper
Full-text available
A Geotechnical Seismic Isolation (GSI) system is proposed in this study based on the use of Rubber-Soil mixtures (RSm) to facilitate the benefits of dynamic soil-foundation structure interaction. The latter is possible due to the lower stiffness and greater capacity to dissipate energy of RSm. However, the research done on RSm has been limited to the element scale context. In this study, the dynamic response of a modified soil foundation has been investigated by adding soft zones comprising RSm. A 1g shaking table was used to apply a sequence of sinusoidal excitations to a soil-lumped mass system. The results have shown that the rubber addition results in a reduction of the amplification at frequencies higher than the system natural frequency. This change in the dynamic response is due to the shift in the natural frequency and the dampening of the peak output accelerations. This study shows thus that an alternative design consideration with bagged soft zones, adjacent to the soil foundation, can offset the incoming disturbances and hence could protect both new and existing constructions.
... Numerous studies investigated the use of scrap tire derivatives in civil engineering applications. For example, Masad et al. (1996), Tweedie et al. (1998), Lee et al. (1999), Abichou et al. (2005), and Shrestha et al. (2016) investigated the materials as lightweight backfill materials; Edil et al. (2004) and Reddy et al. (2010) used them as drainage materials; Wolfe et al. (2004), Hazarika et al. (2008), Tsang (2008), and Hazarika et al. (2010) investigated the effectiveness of these materials for vibration mitigation; Bosscher et al. (1997) studied the use of these materials for highway embankment; use of scrap tire derivatives for soil reinforcement was studied by Foose et al. (1996), Abdrabbo et al. (2005), and Hazarika et al. (2010); and Uchimura et al. (2007) and Kaneko et al. (2013) also studied the use of these materials to counteract liquefaction. ...
Article
With the increasing number of vehicles plying on the roads, alarming volumes of the waste tires are generated every year throughout the globe. The disposal of these materials is of great concern. The most efficient way to reduce their volume is to reuse these materials for various applications. To investigate the behavior of the scrap tire derivatives under cyclic load, a series of cyclic triaxial tests were conducted. Seven different mixes of sand and tire crumbs (by weight) were tested under three different confining pressures (50 kPa, 75 kPa, and 100 kPa) and four different shear strain amplitudes (0.075%, 0.15%, 0.225%, 0.3%). All the tests were reported for 200 loading cycles. The result showed that the addition of tire crumbs reduced the shear modulus and increased the damping ratio. The addition of tire crumbs reduced the modulus degradation rate remarkably and makes the material useful for structures subjected to cyclic loading. The resistance toward liquefaction is also increased drastically upon the addition of tire crumbs, and the mixes showed high resistance toward the generation of excess pore water pressure. The detailed characterization of sand-tire crumbs mixes reported in the present study can be very helpful when choosing the mix for different applications.
... The foundation natural soil material is replaced or modified down to a certain depth (e.g. 2-3 m) by well-controlled low-modulus materials such as rubber-soil mixtures (RSM) (initially proposed in Tsang 2008), in order that the soil-foundation-structure interaction (SFSI) favourably affects the overall structural response. The key advantage of the GSI system is that seismic energy is dissipated before it transmits into the structure, which is fundamentally different from conventional seismic isolation systems or other earthquake protection techniques (Tsang 2009, Karatzia & Mylonakis 2017. ...
... Simul-78 taneously, rubber mixtures can be considered an affordable alternative for the 79 seismic isolation of conventional structures, especially in developing countries. 80 Tsang (2008), in the first systematic numerical study on the effectiveness 81 of the use of a SRM in the seismic isolation of structures, reported that a 82 SRM layer placed underneath a structure could effectively reduce its horizontal 83 and vertical ground motion response. At the same time, its low cost could 84 benefit the developing countries. ...
Preprint
Full-text available
We present the results of the forced-vibration experiments performed at the large-scale prototype structure of EuroProteas founded on gravel-rubber mixture (GRM) layers acting as a means of Geotechnical Seismic Isolation (GSI). Three GRM with different rubber content per mixture weight (0%, 10%, and 30%) but the same mean grain size ratio were used as foundation soil. Each GRM-structure system was subjected to harmonic forces in a wide range of excitation frequencies and force amplitude. It was found that a 0.5m thick GRM foundation soil layer with 30% rubber content can effectively isolate the structure. The strong effect of the rubber fraction was expressed in the detected period elongation and the dominating rocking component which leads to a more "rigid-body" response of the structure. Moreover, the developed base shear and base moment are significantly reduced regardless of the excitation frequency, while the increased damping of the system and the important energy dissipation demonstrate the effectiveness of the GRM foundation soil layer. Overall, the experimental results demonstrated that the use of GRM as a GSI system can be considered as an innovative and low-cost alternative seismic isolation technique.
... Nowadays, the several different kinds of seismic barriers protecting against SAW and a more rear evanescent and head waves, are suggested, with vertical barriers being the most common case [7,[15][16][17][18][19]; less frequent horizontal barriers [15,20]; pile fields intended to scatter the SAW wave energy [20][21][22]; and barriers containing periodic or quasi periodic structural members or metamaterials acting as a phononic crystal [23][24][25][26]. The principal ideas for the use of seismic barriers relate to reflection, refraction, scattering and dissipation energy; the latter mainly refers to the metamaterials with significant inelastic response, and especially to the granular metamaterials. ...
Article
Full-text available
A comparative study of the vertical seismic barriers intended for protecting from Rayleigh seismic waves and filled with (1) homogeneous linearly elastic materials and (2) granular metamaterials, is done by the finite-element (FE) modeling. The granular metamaterial obeys the Mohr–Coulomb plasticity model with the associated flow rule, low cohesion value, and small internal friction and dilation angles. The performed numerical analysis reveals a principal ability achieving much higher reduction ratios for magnitudes of accelerations along with much longer shadow zones behind the barrier for barriers filled with metamaterials in comparison with the purely elastic homogeneous barriers.
... Many studies reported the use of scrap tire derivative and sand composite for different civil engineering applications. The applications include lightweight backfill material (Tweedie et al. 1998;Lee et al. 1999;Masad et al. 1996;Abiuchou et al. 2005;Shrestha et al. 2016), drainage material (Edil et al. 2004;Reddy et al. 2010), vibration reduction (Wolfe et al. 2004;Hazarika et al. 2008;Tsang 2008;Hazarika et al. 2010), highway embankments (Bosscher et al. 1997), soil reinforcement (Foose et al. 1996;Abdrabbo et al. 2005;Hazarika et al. 2010), and others, to name a few. A few studies have also focused on the use of these materials for liquefaction mitigation (Uchimura et al. 2007;Kaneko et al. 2013). ...
Article
Use of scrap tire derivatives for civil engineering applications is an emerging field. In spite of extensive characterization of these materials, most of the studies focused on smaller-sized tire derivatives, i.e., tire crumbs. Furthermore, only a few studies are available on the cyclic response of these tire derivatives. The present study details the dynamic properties and liquefaction behavior of tire chips and sand–tire chip mixes. A series of strain-controlled cyclic triaxial tests were carried out considering confining pressure, strain amplitude, and tire chip content as variables. The tests were performed on seven different mixes with varied proportions of sand and tire chips by weight. The addition of tire chips to the sand increased the liquefaction resistance and threshold shear strain of the mixes significantly. The addition of the tire chips decreased the shear modulus and increased the damping ratio of the mixes. Furthermore, based on the behavior of the mixes with different tire chip contents, an optimum mix was suggested.
... In an attempt to overcome the aforementioned limitations, Tsang (2008) and Tsang et al. (2012) investigated numerically the use of a sand-rubber foundation layer for the seismic isolation of structures in developing countries. This investigation has paved the way for the use of durable, locally available and recyclable materials as a means of a more economical and sustainable approach for the seismic protection of structures in developing countries. ...
Article
Full-text available
The aim of this paper is to demonstrate the efficiency of a low-cost and sustainable timber-based energy dissipation system with recentering ability, which can be used as a seismic isolation system or a tuned mass damper for the seismic protection of structures in developing or developed countries. The system, defined as Dovetail with SPrings (Dove-SP), utilizes the attractive properties of timber to store CO 2 , thus reducing the carbon footprint of the existing energy dissipation systems: It comprises two timber slabs that are designed to slide against each other in a motion that is restrained by a dovetail sliding joint. Two sliding interfaces that allow this sliding motion at an attractively low friction coefficient are experimentally investigated: A PVC sand-wich (PVC-s) sliding interface, comprising a thin layer of sand that is sand-wiched between two PVC layers and a timber sand-wich sliding interface consisting of a thin layer of sand encapsulated between two beech timber surfaces. A set of low-cost steel springs is designed and installed on both sides of the dovetail joint to recenter the structure back to its original position after the end of an earthquake ground motion excitation. A novel, low-cost and deformable wood material fabricated from delignified balsa wood is used to reduce the pounding effects before the activation of the steel springs. The seismic behavior and the recentering ability of the novel timber-based energy dissipation system subjected to an ensemble of recorded earthquake ground motion excitations was experimentally investigated through a large-scale shaking table investigation at ETH Zurich.
... Aimed at providing a sustainable engineering solution to the ELT disposal in New Zealand, the authors have conducted a feasibility study on the use of ELT-derived aggregates (in the form of granulated rubber) blended with gravelly soils as an effective energy-absorption layer for geotechnical seismic-isolation (GSI) with energy dissipation foundation systems for low-rise light-weight residen-tial buildings. Low-shear modulus and high damping materials such as sand-rubber mixtures (SRMs) have been previously proposed for use as GSI layers (Tsang, 2008(Tsang, , 2009Tsang et al., 2012). However, the compressible nature of SRMs in the GSI layer leads to low bearing capacity and unacceptable high settlement of foundations (Dhanya et al., 2018(Dhanya et al., , 2020. ...
Article
Full-text available
In this paper, a newly developed 3-dimentional discrete element model (DEM) for gravel-rubber mixtures (GRMs), namely DEM4GRM, that is capable of accurately describing the macro-scale shear response (from small to large deformation) of GRMs in a direct shear box apparatus is presented. Rigid gravel grains are modelled as simple multi-shape clumps, while soft rubber particles are modeled by using deformable 35-ball body-centered-cubic clusters. Mixtures are prepared with different volumetric rubber content (VRC) at 0, 10, 25, 40 and 100%, statically compressed under 30, 60 and 100 kPa vertical stress and then sheared, by closely simulating a reference laboratory test procedure. The variation of micro-scale factors such as fabric, normal and tangential force anisotropy is carefully examined throughout the shearing process and described by means of novel micro-mechanical relationships valid for GRMs. Moreover , strong-force chains are scrutinized to identify the transition from rigid to soft granular skeleton and gain insights on the load transfer and deformation mechanisms of GRMs. It is shown that the development of the fabric and force anisotropy during shearing is closely related to the macro-scale shear strength of GRMs, and strongly depends on the VRC. Besides, strong-force chains appear to be primarily formed by gravel-gravel contacts (resulting in a rigid-like mechanical behavior) up to VRC = 30%, and by rubber-rubber contacts (causing a soft-like mechanical response) beyond VRC = 60%. Alternatively, at 30% < VRC < 60%, gravel-rubber contacts are predominant in the strong-force network and an intermediate mechanical behavior is observed. This is consistent with the behavioral trends observed in the macro-and micro-mechanical responses.
... In addition, as a siding isolation system, geotechnical seismic isolation techniques using locally available materials such as limestone sand [13], sand-bitumen mixtures [14] and rubber-soil mixtures [15] were developed for structural seismic response mitigation. These techniques are characterized by low cost and simple construction and are of particular significance in developing countries [16][17][18]. ...
Article
Full-text available
Previous studies have proven that adding an inerter to a sliding isolation structure can reduce the isolation displacement without compromising the control effect of the superstructure. However, due to the strong nonlinearity of the sliding isolator, approximate methods or numerical analyses are adopted to investigate inerter-added sliding isolation structures, which hinders the understanding of the inherent working mechanisms of such structures. This study derives exact analytical solutions during both sliding and stick motion states of inerter-added sliding isolation structures under harmonic ground motions and investigates the influence of an additional inerter on the motion states and responses of such structures. The main novelties of this paper are the employment of the inerter technique in a sliding system for performance improvement and explicit expressions of the dynamic responses and motion modes for inerter-added sliding isolation structures that assist in understanding the role of the additional inerter. Differential equations are established for both the stick and sliding motions of inerter-added sliding isolation structures subjected to harmonic ground excitations. The dynamic characteristics of the structure are analyzed, and accurate analytical solutions are derived for structural responses. The explicit forms for the occurrence conditions of three fundamental modes (i.e., the stick-stick, stick-slip and slip-slip modes) for the motion of the inerter-added sliding isolation structures are presented. Based on the derived analytical solutions, extensive parametric analyses are conducted to investigate the influences of the added inerter on the motion modes and responses of sliding isolation structures. By adding an inerter, a decreased natural frequency, a decreased damping ratio and a reduction in ground motion excitation are observed for the vibration of the superstructure in the inerter-added sliding isolation structure compared to that in the sliding isolation structure without an inerter. Furthermore, the inerter causes the slip-slip mode to occur more easily, which is preferred for sliding isolation structures when sliding occurs. An increasing inertance of the inerter is beneficial for reducing isolation displacement in general but contrary to reducing maximum acceleration in some frequency ranges and excitations with large amplitudes. The trade-off between the reduction of isolation displacement and acceleration is recommended for determining the inertance of the inerter in sliding isolation structures.
... In between, even if they are very common materials, systems composed of grains with very different-soft and hard-rheologies, driven far above the jamming transition, have a bewildering but fascinating behavior that remains mostly misunderstood. They have been experimentally studied in very specific applications, such as stress release [26,27], seismic isolation [28,29], and foundation damping [30,31]. However, to the best of our knowledge, no local measurements have been performed to understand the microprocesses leading to their characteristic macroscopic behavior. ...
Article
In this Letter, we report on an experimental study which analyzes the compressive behavior of two-dimensional bidisperse granular assemblies made of soft (hyperelastic) and hard grains in varying proportions (κ is the portion of soft grains). By means of a recently developed uniaxial compression setup [Vu and Barés, Phys. Rev. E 100, 042907 (2019)]2470-004510.1103/PhysRevE.100.042907 and using an advanced digital image correlation method, we follow, beyond the jamming point, the evolution of the main mechanical observables, from the global scale down to the strain field inside each deformable grain. First, we validate experimentally and extend to the uniaxial case a recently proposed micromechanical compaction model linking the evolution of the applied pressure P to the packing fraction ϕ [Cantor et al., Phys. Rev. Lett. 124, 208003 (2020)]0031-900710.1103/PhysRevLett.124.208003. Second, we reveal two different linear regimes depending on whether the system is above or below a crossover strain unraveling a transition from a discrete to a continuous-like system. Third, the evolution of these linear laws is found to vary linearly with κ. These results provide a comprehensive experimental and theoretical framework that can now be extended to a more general class of polydisperse soft granular systems.
Article
Seismic tunnel-soil-building interaction in high plasticity soft clays can led to important ground motion variability that affect medium to low rise buildings located adjacent to the underground structure. This paper presents a numerical study aiming at establishing the performance of an enhanced foundation system to be used as a mean to reduce detrimental interaction and enhanced the seismic performance of mid to low buildings located nearby tunnels. Initially, interaction effects are revised considering the effect that frequency content, intensity, and strong ground motion duration have on the interplay between incoming seismic waves reflected in the tunnel, and the energy feeding back from the building swinging back and forth during a large earthquake. Series of three-dimensional finite difference models were developed. Seismic analyses considered both normal and subduction events with a return period of 250 years were carried out. Finally, the seismic performance of the enhanced foundation system was established. From the results gathered in here, it was clearly established the effectiveness of the proposed system to reduce both foundation ground motions and building seismic demand.
Article
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In this paper, more than 70 large-scale pullout tests were performed to evaluate the performance of an innovative composite geosynthetic strip (CGS) reinforcement in sandy backfill. The CGS reinforcement is composed of a geosynthetic strip (GS) and parts of a scrap truck tire as transverse members. The experimental pullout results for the CGS reinforcement were compared with the suggested theoretical equations and ordinary reinforcements, including the GS, the steel strip (SS), and the steel strip with rib (SSR). The pullout test results show that adding three transverse members to the GS reinforcement (CGS3) with S/H=6.6 (where S and H are the space and height of the transverse members, respectively) increases pullout resistance by more than 120%, 170%, and 50% compared to the GS, the SS, and the SSR, respectively. This result shows that the CGS3 (CGS with three transverse members) reinforcement needs at least 55.5%, 63%, and 33.3% smaller length compared to the GS, the SS, and the SSR, respectively. In general, implementation of mechanically stabilized earth wall (MSEW) with the proposed strip may help geotechnical engineers prevent costly designs and solve the problem of MSEW implementation in cases where there are limitations of space.
Article
Rubber–soil mixtures (RSM), formed by mixing two types of granules with vastly different mechanical properties, has the potential for serving as a cost-effective substitute for geotechnical fillings. Its micromechanical behavior at a microscopic scale, however, is not yet well understood. In this study, a numerical model of granulated RSM under biaxial compression conditions is established based on the discrete element theory and two-dimensional particle flow code. Microparameters of a particular RSM are studied and calibrated by comparison with triaxial consolidated drained shear tests. The volumetric fraction of sand is assigned as the index of the mixture, and the deviatoric stress–axial strain curves of RSM with different sand fractions are analyzed. Particle rotation, average coordination number, force chain structure, and energy dissipation with axial strains are further investigated to better understand the microscopic mechanisms of RSM. The main findings of the study include: (1) Rubber particles are highly deformable and fill the voids more easily than stiffer sand particles. This contributes to the high friction of sand–rubber interfaces, which delays or even inhibits the relative motion and tumbling of sand particles; (2) The force chains of sand particles are either braced from buckling until large axial strains by rubber particles occupying the intergranular voids or distributed by increased rubber–rubber contacts depending on the rubber content; and (3) RSM with a rubber volumetric content of 30–40% are optimal in that the force chain increases monotonically with axial strain with a stable load-deformation relationship. In addition, the sensitivity analysis of the effect of microparameters on the macroscopic behavior of RSM is presented, which can provide theoretical support for exploring the mechanical properties of similar mixed granular materials subjected to external loading.
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Large numbers of vehicles manufactured annually result in massive traffic and in turn creates huge numbers of waste tires entering into the environment and causing problems. Therefore, it is necessary to find reasonable applications for waste tires. They may be used to reduce seismic effects on structures due to their damping characteristics and energy absorption. Although comprehensive research studies have been carried out on static and dynamic properties of soil mixed with waste rubber, dynamic tests on layered mixtures of sand and rubber are highly demanding due to their easy to perform for practical applications. In this study, dynamic properties of sand mixed with different percentages of waste tire grains in uniform and layered forms were studied using a series of consolidated drained cyclic triaxial tests. The results show that for a given rubber percentage, layered mixtures have less shear modulus and more damping ratio than rubber-sand mixtures with uniform distribution. It has also been observed that for 50% tire content in layered sand-rubber mixtures, the Sand-Tire-Sand (STS) configuration offers lower shear modulus and a greater damping ratio than the Tire-Sand-Tire (TST) arrangement.
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Earthquake-induced liquefaction increases the pore water pressure, reducing soil stiffness and allowing lateral movement of crust layer above the liquefiable layer, considerably damaging the piles. In this paper, an attempt is made to investigate the response of piles under liquefaction using a spectrum-compatible accelerogram corresponding to the maximum credible earthquake for the most severe seismic zone of Indian standards, with finite element model (FEM) in the OpenSees platform. It is predicted that the maximum pile head deflection, bending moment, and shear force is 3.66, 15.31, and 3.09 times that pile responses due to non-liquefied soil condition, respectively. Further, a mitigation technique is proposed using rubber–soil mixture (RSM) around the pile. It is estimated that a 10% reduction in maximum pile head displacement is achieved with 1-m depth RSM layer, while the reduction of 40% and 60% is achieved with RSM depth 2.5m and 4m, respectively. Responses due to proposed FEM modeling in close agreement with that of SAP modeling using the Euler–Bernoulli-beam model.
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Soilbags have been successfully used in the reinforcement of building foundations that can function as the base isolation. A series of unconfined compression tests under monotonic and cyclic loading were conducted to investigate the static bearing capacity and the dynamic deformation behaviour of stacked soilbags. The results of monotonic loading tests demonstrate that the ultimate compressive strength and the tangent compression modulus of soilbags tend to relatively stable values of around 0.7 MPa and 6.73 MPa, respectively, when the number of layers exceeds three. Under cyclic loading, the accumulated vertical strain of stacked soilbags increases nonlinearly under the application of cyclic loading, reducing with each loading cycle and even reaching a relatively stable state where the vertical strain is primarily elastic, which can be described with an empirical formula with respect to the static vertical stress, the cyclic load ratio and the number of loading cycles. The resilient moduli of stacked soilbags change slightly during cyclic loading period, and increase with the increasing static vertical stress and the decreasing cyclic load ratio. The outcomes of this study demonstrate the feasibility of soilbags as the base isolation as they have prominent bearing capacity and stable deformation behaviour under cyclic loading.
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As reuse materials, waste tires mixed with soils are valuable materials to be used for many purposes in geotechnical projects that may be subjected to dynamic loads. The aim of this study is to assess the efficacy of using waste tires in buried pipe protection. To achieve this purpose, a series of laboratory model tests were carried out to investigate the dynamic responses of pipe buried in pure soil and rubber soil mixtures with volume content of 10%, 20% and 30% rubber particles. Test results such as earth pressure and strain of buried pipe are discussed in this study. The results indicate that inclusion of 20%-30% rubber particles in the mixtures leads to a change in earth pressure increment distribution, and these mixtures leads to obvious reductions in earth pressure increments. For the mixtures with 20%-30% rubber particles, the pipe has lower strain under the dynamic loading. Compared with pure soil, the mixtures with 20%-30% rubber particles exhibit better performances in regards to responses of pipe-soil system. Hence, the research undertaken in this paper provides a viable approach to protect the buried pipe subjected to dynamic loading.
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Understanding and quantifying the long-term deformation behaviour of granular materials under repeated loads is imperative for ensuring the longevity of railway tracks. One of the most relevant characteristics of granular materials under repeated cycles of loading and unloading is their ability to achieve a relatively stable state (shakedown) after being subjected to initial compression. The shakedown response of blended rubber-granular waste mixtures under triaxial test conditions has been studied by past studies highlighting the influence of the rubber content, confining stress, and cyclic loading amplitude. However, a clear methodology for estimating shakedown yield limits of these granular mixtures has not been discussed in detail. The current study highlights the influence of peak shear strength of these mixtures under static loading on their shakedown response in cyclic loading conditions. It is observed that the variation of static shear strength with rubber contents and confining stresses is found to affect the shakedown response. A unified method of estimating the shakedown limit is proposed by analysing permanent axial strains with normalised cyclic stress ratio at different loading cycles. The proposed method is validated through two independent sets of drained cyclic triaxial test data on coal wash-rubber crumb mixtures and rail ballast.
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The paper focuses on the detailed analysis of the dynamic characterisation of polyurethane to evaluate the effects of polyurethane injections into the soil with the aim of geotechnical seismic isolation (GSI). To determine the dynamic properties, resonant column (RC) tests were performed at the University Kore of Enna (Italy) on specimens of pure polyurethane (PUR) with different values of density and subjected to different mean confining pressures. The results obtained by means of RC tests, in terms of shear modulus G and the damping ratio D as a function of shear strain γ c , allowed to develop an analytical formulation for G- γ c and D- γ c curves, taking into account the linear relationship with density of both the maximum value of shear modulus G max and the minimum value of damping ratio D min . The analytical formulation derived from the experimental results is applied for ground response seismic analyses of cohesive soils injected with polyurethane, using a finite element code. The numerical results show that the polyurethane injections reduce the value of maximum acceleration at ground surface and the reduction ranges with the thickness of the soil involved by polyurethane injection.
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Characteristics of response spectra of free‐field vertical ground motion recorded during the 1994 Northridge earthquake are examined. Dependence of vertical and horizontal response spectra, and their ratio, on the site‐to‐source distance is investigated through development of attenuation relationships for vertical and horizontal spectral ordinates. The database includes 123 response spectra of the motions recorded at 41 alluvial sites. Vertical‐to‐horizontal (V/H) response spectral ratio is found to be strongly dependent on period and distance of site to the seismic source. V/H spectral ratio largely exceeds the commonly assumed value of 2/3, at short periods in the near‐field region. The main characteristics of V/H spectral ratio for the Northridge earthquake are found to be qualitatively similar to those observed in the 1989 Loma Prieta, California, and in several other earthquakes recorded over the SMART‐1 array in Taiwan. These characteristics are very likely to be universal.
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Although the fact that sediments can amplify earthquake ground motion was recognized at least 100 years ago (Milne, 1898), there has been a lingering uncertainty as to whether the degree of amplification varies with the level of input motion. This issue remains as one of the most important questions with respect to understanding and predicting earthquake ground motion. In accordance with the conservation of energy, seismicwave amplitudes generally increase in sediments due to lower densities and and/or lower seismic velocities. In addition, resonance effects can occur where abrupt impedance contrasts exist. If sediments were perfectly elastic, their response would be independent of incident-wave amplitudes. As with any real material, however, sediments begin to yield at some level of strain, and this violation of Hooke's law will give rise to a nonlinear response. The engineering community has long believed that sediment nonlinearity is significant. This perspective was based almost entirely on...
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This paper considers the potential usage of a rubber-soil mixture beneath the foundation of a building in order to reduce the induced seismic loads. The appropriateness of replacing backfill soil by a granulated rubber-soil mixture, as a kind of distributed seismic isolation system, is assessed through numerical simulations using the finite element method. Specifically, the effect of utilizing rubber-soil mixtures in the foundation soil of a 5-storey building on its seismic behaviour is studied by comparing the computed seismic responses with those calculated using the corresponding system without the replacement of the foundation soil. Numerical simulations and parametric analyses are conducted, using a commercially available software (SAP2000), in order to study the effect of certain soil parameters and earthquake characteristics. The effectiveness of using a rubbersoil mixture on the dynamic response of the simulated structure is discussed in terms of peak absolute top-floor accelerations.
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In this paper the effect of the vertical motion on the response of R/C frames is investigated. An analytical model, which was developed with the possibility to consider the effects of uncoupled axial force variations, such as caused by the vertical motion, was used. The analysis concern a five-story frame subjected to different strong motion records. A comparison of the response with and without the vertical component was performed. The results confirmed that the vertical excitation could have a detrimental effects on the damage of R/C frames, and on the various aspects of its response, particularly as a consequence of a deterioration of the column behaviour.
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This paper describes the design and construction of a twelve storey office building which has base isolators (i.e. energy dissipators) and external cross bracing to resist lateral loads. The computer analysis techniques used are described and some comparisons are made with non-base isolated structures. The system shows a practical method of using base isolation and energy dissipation techniques in a multi-storey structure. The construction of the building has proved the system to be advantageous in terms of both cost and construction time.
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The objective of this study was to investigate the feasibility of using shredded waste tires to reinforce sand. Direct shear tests were conducted on mixtures of dry sand and shredded waste tires. The following factors were studied to evaluate their influence on shear strength: normal stress, sand matrix unit weight, shred content, shred length, and shred orientation. From results of the tests, three significant factors affecting shear strength were identified: normal stress, shred content, and sand matrix unit weight. A model for estimating the strength of reinforced soils was also evaluated to determine its applicability to mixtures of sand and tire shreds. When the model is calibrated using results from one shred content, it may be useful for estimating the friction angle for other shred contents. In all cases, adding shredded tires increased the shear strength of sand, with an apparent friction angle ({phi}{prime}) as large as 67{degree} being obtained. Shred content and sand matrix unit weight were the most significant characteristics of the mixes influencing shear strength. Increasing either of these variables resulted in an increase in {phi}{prime}. Tests were also conducted on specimens consisting of only shredded tires (no sand), and the friction angle obtained was 30{degree}.
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Processed waste tires mixed with soils are applicable in lightweight fills for slopes, retaining walls, and embankments that may be subjected to seismic loads. Rubber's high damping capacity permits consideration of granulated rubber/soil mixtures as part of a damping system to reduce vibration. The dynamic properties of granulated rubber/soil mixtures are essential for the design of such systems. This research investigates the shear modulus and damping ratio of granulated rubber/sand mixtures using a torsional resonant column. Specimens were constructed using different percentages of granulated tire rubber and Ottawa sand at several different percentages. The maximum shear modulus and minimum damping ratio are presented with the percentage of granulated rubber. It is shown that reference strain can be used to normalize the shear modulus into a less scattered band for granulated rubber/sand mixtures. The normalized shear modulus reduction for 50% granulated rubber (by volume) is close to a typical saturated cohesive soil. Empirical estimation of maximum shear modulus of soil/rubber mixtures can be achieved by treating the volume of rubber as voids.
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The primary objective of the research described herein is to assess the pertinent engineering properties for reusing shredded scrap tires as a construction material for light-weight fill material in highway construction, for drainage material in highway and landfill construction, and for other similar applications. Reuse of scrap tires would not only provide a means of disposing of them but would also help solve difficult economical and technical problems. This paper presents the characteristics of shredded scrap tires and their engineering properties and behavior alone or when mixed with soils. The properties considered include compaction, compressibility, strength and deformability, and hydraulic conductivity. Described are new test procedures or modification of existing methods developed to characterize this unusual material.
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The United States Environmental Protection Agency (USEPA) estimates that over 279 million discarded tires are being added annually to the already existing stockpile of two billion tires. Current disposal and stacking methods of waste tires are not acceptable due to the possibility of fire and health hazards. Several states and the federal government have issued legislation that encourages or mandates the recycling of discarded tires. One application where shredded tires can be used is as a lightweight fill material behind retaining walls or in highway embankments over weak or compressible soils. This paper presents the engineering properties of shredded tires, Ottawa sand, and a mixture of 50% Ottawa sand and 50% shredded tires by volume (70% Ottawa sand and 30% shredded tires by weight). The maximum size of the tire chips used was 4.75 mm. Gradation, specific gravity, void ratio, density, permeability, and consolidated-drained (CD) triaxial tests were performed as part of the testing program. Although the data obtained were limited to the above three mixes, the results indicate that the use of shredded tires/Ottawa sand mixes as a lightweight fill material is very promising. However, long-term impact of leachates from tires on groundwater quality should be investigated.
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The growing interest in utilizing waste materials in civil engineering applications has opened the possibility of constructing reinforced soil structures with unconventional backfills. Scrap tires are a high-profile waste material for which several uses have been studied, including the use of shredded tires as backfill. A triaxial testing program was conducted to investigate the stress-strain relationship and strength of tire chips and a mixture of sand and tire chips. The test results and additional information from the literature were used in the numerical modeling of wall backfills, both unreinforced and reinforced with geosynthetics. The numerical modeling results suggest tire shreds, particularly when mixed with sand, may be effectively used as a backfill.
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Masonry infill walls are widely used as partitions worldwide. Field evidence has shown that continuous infill masonry walls can help reduce the vulnerability of a reinforced concrete structure. In order to test this hypothesis, a full-scale three-story flat-plate structure was strengthened with infill brick walls and tested under displacement reversals. The results of this test were compared with results from a previous experiment in which the same building was tested without infill walls. In the initial test, the structure experienced a punching shear failure at a slab-column connection. The addition of infill walls helped to prevent slab collapse and increased the stiffness and strength of the structure. The measured drift capacity of the repaired structure was 1.5 %. A numerical model of the test structure was calibrated to match experimental results. Numerical simulations of the response of the strengthened structure to several scaled ground motion records suggest that the measured drift capacity would not be reached during strong ground motion.
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The vertical component of earthquake ground motion has generally been neglected in the earthquake-resistant design of structures. This is gradually changing due to the increase in near-source records obtained recently, coupled with field observations confirming the possible destructive effect of high vertical vibrations. In this paper, simple procedures are suggested for assessing the significance of vertical ground motion, indicating when it should be included in the determination of seismic actions on buildings. Proposals are made for the calculation of elastic and inelastic vertical periods of vibration incorporating the effects of vertical and horizontal motion amplitude and the cross-coupling between the two vibration periods. Simplified analysis may then be used to evaluate realistic vertical forces by employing the vertical period of vibration with pertinent spectra without resorting to inelastic dynamic analysis.
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Near source earthquakes can be characterized not only by strong horizontal but also by strong vertical ground motions with broad range of dominant frequencies. The inelastic horizontal response of thin-walled L-shaped steel bridge piers, which are popularly used as highway bridge supports, subjected to simultaneous horizontal and vertical ground excitations of near source earthquakes is investigated. A comprehensive damage index and air evolutionary-degrading hysteretic model are applied. Numerical analysis reveals that the strong vertical excitation of a near source earthquake exerts considerable influences on the damage development and horizontal response of thin-walled L-shaped steel bridge piers.
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This paper presents the results of different numerical analyses (nonlinear dynamic FEM simulations) regarding the monumental buildings in Ripabottoni village (Campobasso, southern Italy), which were damaged by the 2002 Molise earthquake. In particular, the church of S. Maria Assunta, for which typological data and an exhaustive damage survey are available, is taken into account. Some preliminary studies [Spallarossa et al., 2004], which correlate the waveform of the available recordings from aftershocks and the surveyed damage mechanism (due to the crushing of the vertical structural elements), suggested that a feasible explanation for this particular damage pattern does not involve only the intrinsic vulnerability of this type of buildings, but deals also with the high energy content in the high frequency range observed in the vertical component of the seismic events. In order to understand the structural damage patterns surveyed, synthetic accelerograms, representative of the main shock (M-l = 5.4 on 31 October 2002), were computed. The Empirical Green Function (EGF) method was applied to compute the seismic input adopted in the nonlinear dynamic analyses that we performed for the church of S. Maria Assunta. The results confirm that the observed damage pattern cannot totally be put down to the vulnerability of the building, but the particular characteristics of the seismic action played a fundamental role in determining it.
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Geotechnical models consistently indicate that the stress-strain relationship of soils is nonlinear and hysteretic, especially at shear strains larger than ∼10-5 to 10-4. Nonlinear effects, such as an increase in damping and reduction in shear-wave velocity as excitation strength increases, are commonly recognized in the dynamic loading of soils. On the other hand, these effects are usually ignored in seismological models of ground-motion prediction because of the lack of compelling corroborative evidence from strong-motion observations. The situation is being changed by recently obtained data. Explicit evidence of strong-motion deamplification, accompanied by changes in resonant frequencies, are found in the data from the 1985 Michoacan, Mexico, and the 1989 Loma Prieta, California, earthquakes, the events recorded by the vertical and surface accelerograph arrays in Taiwan, as well as a number of other events throughout the world. Evidence of nonlinear behavior becomes apparent beyond a threshold acceleration of ∼100 to 200 gal. Nonlinearity is considerable in cohesionless soil but may be negligible in stiff soils. The findings of recent years indicate that nonlinear site effects are more common than previously recognized in strong-motion seismology.
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An acoustic model employing sound waves in a fluid medium was used to evaluate the use of rows of piles as passive isolation barriers to reduce ground vibrations. The results of experimental measurements indicate that the effectiveness of the barriers is highly dependent on the mismatch between pile and soil material properties, with greater mismatch resulting in greater effectiveness. Pile-to-pile aperture spacing of 0. 4 times the wavelength was found to be the upper bound for a barrier to have some effectiveness, and a minor dependence of effectiveness on the pile diameter was also observed. The extrapolation of the model studies to actual field problems is considered.
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Tire chips made from waste tires have a compacted dry unit weight of 40 pcf (0.64 Mg/m3) and a specific gravity of 1.05 making their use as lightweight fill for highway embankments over compressible soils very advantageous. A large scale compressibility apparatus with the capability to measure side friction and horizontal stress was fabricated. Compressibility tests showed that tire chips were very compressible at low stresses but that compressibility decreased significantly at higher stresses. The coefficient of lateral earth pressure at rest was about 0.40 at low stresses and about 0.94 at high stresses. Preliminary finite element studies showed the importance of the thickness and modulus of the subbase overlying the tire chips on pavement deflections.
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A typical engineering approach to developing site-specific design ver- tical ground motions starts with rock-outcrop horizontal motions, converts them into the vertical component using an empirical vertical-to-horizontal (V/H) ratio for re- sponse spectra, and propagates the resulting motion through the soil column as a vertically incident P wave. In the absence of data on strain-dependent soil properties in compressional deformation, strain-compatible shear-wave properties from the horizontal-component analyses are utilized. This approach makes two assumptions: (1) that the vertical motions are primarily composed of compressional waves and (2) that strain-dependent material properties in shear deformation can be extrapolated to compressional deformation. Our study deals with the empirical validation of both assumptions. First, we investigated the ratio of SV -t oP-wave spectra of the vertical component of ground motions from significant recent events in California to find which wave type predominantly contributed to vertical motions, in the frequency range of 0.5-25 Hz. The results indicate that shear waves dominate the vertical motions at frequencies up to approximately 10 Hz, above which the contribution of compressional deformation is about as strong or greater. This result holds for both soil and rock sites. Second, using the data from the KiK-net borehole arrays in Japan, we estimated the nonlinearity in compressional deformation by studying P-wave amplification at variable amplitude levels. Frequency shifts and in some instances reduced amplification, compatible with the hysteretic softening type of nonlinearity known for shear waves, is found as the amplitude of compressional strain increases. A tentative curve of constrained-modulus reduction is also similar to the existing shear-modulus reduction curves. The results of this study suggest that, for most practical applications, vertical motions can be modeled as nonvertically propagating SV waves. This could be im- plemented through conventional one-dimensional horizontal-component modeling using SHAKE and the application of empirical depth-dependent V/H correction factors to account for the inclined propagation path. At high frequencies, vertical motions may have to be modeled as near-vertically propagating P waves, with strain- dependent properties specifically developed for compressional deformation; how- ever, these frequencies may be of lesser importance for design applications.
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Tire shred processors use various mechanical means to reduce the waste stream of tires to components including rubber and steel. There is a stockpile of shredded rubber material in many states that is currently marketed mainly for use as Tire Derived Fuel (TDF). Civil engineering applications such as light landfill cover, and potentially landfill drainage layers are also attractive applications for shredded rubber material. Local environmental protection agencies and state public health officials have been reluctant, however, in some regions to allow recycled rubber to be used in civil engineering applications. An absence of data concerning long-term effects is often cited as justification for these bans. We summarized recent laboratory investigations conducted to quantify possible leachates from various recycled tire compounds. Extension of these results to reported field tests detailing the impact of recycled rubber on air, soil and water quality is also considered, as well as biological and toxicity issues. Finally, we identify areas where additional research is required and suggest approaches supporting "Better Use Determinations" for use of recycled tire rubber in these applications.
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In this study, an experimental investigation program on a newly proposed seismic isolation technique, namely “Geotechnical Seismic Isolation (GSI) system”, is conducted with an aim of simulating its dynamic performance during earthquakes. The testing procedure is three-fold: (1) A series of cyclic simple shear tests is conducted on the key constituent material of the proposed GSI system, i.e., rubber-sand mixture (RSM) in order to understand its behavior under cyclic loadings. (2) The GSI system is then subjected to a series of shaking table tests with different levels of input ground shakings. (3) By varying the controlling parameters such as percentage of rubber in RSM, thickness of RSM layer, coupled with the weight of superstructure, a comprehensive parametric study is performed. This experimental survey demonstrates the excellent performance of the GSI system for potential seismic hazard mitigation.
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The effects of seismic base isolation on the response of structures supported on pile foundations are discussed. The benefit of seismic isolation is achieved by means of flexible piles that may be partially embedded in an inelastic material and that direct substantial energy dissipation and radiation into the surrounding soil. The resulting dynamic characteristics of such a system are found to be considerably different from those of the structure with a fixed base. Using a finite element model developed in a companion paper, the influence of the key parameters affecting the response are studied. A lumped-mass building model with a variety of subsurface conditions is analyzed for free vibration, under constantamplitude ground acceleration, and under horizontal ground accelerations from representative earthquakes. The studies reveal that the interactive flexible-pile system is effective as a base-isolation mechanism.
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The liquefaction of loose, saturated soils is a phenomenon observed since human beings began recording the effects of earthquakes. Whether expressed as sand boils, flow slides, or simply foundation distress, it is widespread and requires careful attention by engineers, who must recognize its potential and prevent its occurrence, or deal with its consequences. While qualitative descriptions of liquefaction and sand boils abounded in the early literature, the extensive and costly liquefaction failures during the 1964 earthquakes at Anchorage, Alaska and Niigata, Japan prompted the geotechnical research community to undertake serious study of the problem. The result is that, over the last thirty-five years, the geotechnical engineering communities in Japan and the United States have developed a sophisticated understanding of the behavior of soils under dynamic and cyclic loading. Many questions remain unanswered, and there is a lot of controversy over important issues, but the research community has answered the central...
Conference Paper
This paper presents a promising earthquake protection method by placing rubber-soil mixtures (RSM) around underground tunnels for absorbing vibration energy and exerting a function similar to that of a cushion. The validity of the method will be demonstrated by numerical simulations using various recorded earthquake ground motions. The use of scrap tires as the rubber material can provide an alternative way of consuming huge stockpiles of scrap tires from all over the world. Moreover, the low cost of this proposed method can greatly benefit developing countries where resources and technology are not adequate for earthquake mitigation using welldeveloped, yet expensive, techniques.
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In seismic design of RC piers, designers usually do not consider that effect of vertical motion is important because horizontal motion usually has the most significant effect on behavior of bridge piers. However, in many earthquakes of the last decades, vertical component was high relative to horizontal motion. The Great Hanshin earthquake on January 17, 1995, was characterized by its high horizontal peak acceleration (0.8 g in some sites) and its high vertical or up-down motion which reached 0.6 g in some sites. In this study, nonlinear 3D FEM approach was used to analyze the effect of vertical motion on inelastic behavior of RC bridge piers. Inelastic behavior was represented by failure mode and ductility level of such piers. We found that vertical motion caused change of final failure collapse of some of the studied piers from flexural to severe diagonal shear failure. For other cases, failure mode did not change but severity of diagonal cracking was higher due to HZ & VL motions than that due to HZ motion only. It is concluded that vertical motion is one reason of such severe collapse of bridge piers during an earthquake in addition to the other two main reasons of the insufficient shear reinforcement ratio and the characteristics of input motion. We concluded that vertical component of motion has remarkable effect on accelerating occurrence of diagonal failure and it was one of the reasons of such severe collapse of the bridge piers during Great Hanshin earthquake in addition to other main reasons which included the insufficient shear reinforcement ratio and characteristics of input motion. We concluded that effect of vertical component of motion should be included in seismic design of RC piers and we have already introduced two aspects by which the designer can include the effect of vertical motion on seismic design of piers; first is to modify the axial compressive stress level and hence the required shear reinforcement ratio and second is to modify ductility level of piers.
Article
Near source earthquakes can be characterized not only by strong horizontal but also by strong vertical ground motions with broad range of dominant frequencies. The inelastic horizontal response of thin-walled L-shaped steel bridge piers, which are popularly used as highway bridge supports, subjected to simultaneous horizontal and vertical ground excitations of near source earthquakes is investigated. A comprehensive damage index and an evolutionary-degrading hysteretic model are applied. Numerical analysis reveals that the strong vertical excitation of a near source earthquake exerts considerable influences on the damage development and horizontal response of thin-walled L-shaped steel bridge piers.
Article
Subsoil interventions to enhance the static soil resistance and reduce deformations may alter significantly the seismic response of the complex soil-foundation-structure system. The aim of this article is to have an insight in the physics of the problems encountered and to validate an adequate numerical modeling procedure to study these effects of the intervention in the global response of the system. Validation concerns wave propagation, site effects, and dynamic soil-structure-interaction issues including the intervention beneath the foundation. Theoretical models-expressions and experimental results from centrifuge tests have been used. The proposed numerical model is proven very efficient to describe the complex dynamic phenomenon and anticipate the seismic response after the employment of subsoil interventions.
Article
The feasibility of constructing buildings on horizontally flexible foundations to mitigate the effects of earthquakes is investigated. The flexibility is achieved by inserting a soft spring between the building superstructure and the soil foundation. The use of slender piles enclosed in sleeves is found to permit flexural distortion. The piles are designed by a simple procedure using smoothed response spectra. The performance of building-foundation systems so designed are then studied using histories of actual ground motions. It is shown that the simple design procedure is adequate and that the concept achieves the desired result of greatly reducing seismic forces. The maximum seismic forces on the building may be reduced to a level which is so low that the forces probably do not affect the design of the superstructure. The economic feasibility of the concept is analyzed and it is shown that the additional foundation cost can be justified on the basis of savings in initial superstructure cost and in probable future damage costs.
Article
This paper describes an experimental and theoretical study of the feasibility of using fiber reinforcement to produce lightweight low-cost elastomeric isolators for application to housing, schools and other public buildings in highly seismic areas of the developing world. The theoretical analysis covers the mechanical characteristics of multi-layer elastomeric isolation bearings where the reinforcing elements, normally steel plates, are replaced by a fiber reinforcement. The fiber in the fiber-reinforced isolator, in contrast to the steel in the conventional isolator (which is assumed to be rigid both in extension and flexure), is assumed to be flexible in extension, but completely without flexure rigidity. This leads to an extension of the theoretical analysis on which the design of steel-reinforced isolators is which accommodates the stretching of the fiber-reinforcement. Several examples of isolators in the form of long strips were tested at the Earthquake Engineering Research Center Laboratory. The tested isolators had significantly large shape factors, large enough that for conventional isolators the effects of material compressibility would need to be included. The theoretical analysis is extended to include compressibility and the competing influences of reinforcement flexibility and compressibility are studied. The theoretical analysis suggests and the test results confirm that it is possible to produce a fiber-reinforced strip isolator that matches the behavior of a steel-reinforced isolator. The fiber-reinforced isolator is significantly lighter and can be made by a much less labor-intensive manufacturing process. The advantage of the strip isolator is that it can be easily used in buildings with masonry walls. The intention of this research is to provide a low-cost lightweight isolation system for housing and public buildings in developing countries.
Article
The concept of seismic or base isolation as a means of earthquake protection seems to be more than 100 years old. However, until very recently, few structures were built using this principle. Today the concept has matured into a practical reality and is taking its place as a viable alternate to conventional (fixed base) seismic resistant construction. This paper reviews some of the history of isolation and restates the basic elements of a modern isolation system. It then proceeds to review current activity, worldwide. Progress in the United States is discussed first followed by that in China, France, Greece, Italy, Japan, New Zealand and the Soviet Union. Directories of isolated structures in the United States, New Zealand and Japan are also included. Finally the performance of a selection of these structures during actual earthquakes is given.
Article
An updated state-of-the-art review of the behaviour of base-isolated buildings to seismic excitation is presented. The review includes the literature on theoretical aspects of seimic isolation parametric behaviour of base-isolated buildings and experimental studies to verify some of the theoretical findings. A brief review of the earlier and current base-isolation devices is given, and aspects for future research are included. -from Authors
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A study on the influence of the plasticity index (PI) on the cyclic stress-strain parameters of saturated soils needed for site-response evaluations and seismic microzonation is presented. Ready-to-use charts are included, showing the effect of PI on the location of the modulus reduction curve G/G(max) versus cyclic shear strain-gamma-c, and on the material damping ration gamma-versus-lambda-c curve. The charts are based on experimental data from 16 publications encompassing normally and overconsolidated clays (OCR = 1-15), as well as sands. It is shown that PI is the main factor controlling G/G(max) and lambda for a wide variety of soils; if for a given gamma-c PI increases, G/G(max) rises and lambda is reduced. Similar evidence is presented showing the influence of PI on the rate of modulus degradation with the number of cycles in normally consolidated clays. It is concluded that soils with higher plasticity tend to have a more linear cyclic stress-strain response at small strains and to degrade less at larger gamma-c than soils with a lower PI. Possible reasons for this behavior are discussed. A parametric study is presented showing the influence of the plasticity index on the seismic response of clay sites excited by the accelerations recorded on rock in Mexico City during the 1985 earthquake.
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