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Pilotis buildings have widely spread out in developed countries since World War II onwards. From the structural point of view, Pilotis RC frames exhibit substantial lack in ductility capacity and shear resistance localized at the first floor, since they have been mainly realized before the seismic codes’ era. The present study shows the performance...
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... study has been conducted for a typical pilotis RC frame system designed for gravity loads only during the decade '60-'70s in Italy, with a 12.45 × 36 m rectangular base, and seven floors for a total of 22 m high. Structural plan and views are presented in Figure 1 while RC materials information are reported in Table 1, as derived by a preliminary on-site investigation. Main beams span in transversal direction (named X direction) while only perimetric secondary beams connect main beams in longitudinal direction (named Y direction). ...
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... beams span in transversal direction (named X direction) while only perimetric secondary beams connect main beams in longitudinal direction (named Y direction). The building was first conceived to host essential functions, including public administration functions and directional offices: this led to different interstorey heights, as highlighted from the frontal views of Figure 1b A nonlinear time history analysis has been performed in order to accurately evaluate the case study structural performance under seismic action. The considered building is located in one of Italian highest seismic risk zones, characterized by a Peak Ground Acceleration (PGA) of 0.36 g and Soil Amplification Factor of 1.17. ...
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... panels have been dived into groups that consider interstory heights and panels geometry as well, obtaining the nine different acronyms of Figure 8. F1, F2, and F3 characterize three different interstorey heights: F1 is used for the second storey height, F2 for the third, fourth, and fifth storey heights, and F3 for the sixth storey height. A and B characterize the transversal and longitudinal building sides, as shown by Figure 1b,c, respectively. Lastly, L and C characterize lateral and central infill panels, respectively, of the transversal building side. ...
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... storey shear forces and displacements are plotted in Figure 10 charts for both X and Y direction. Maximum storey shear forces are 3500 kN and 5500 kN in X and Y directions, respectively. ...
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... ratios, pr, are plotted in Figure 11 charts. The RC beams and columns show a good performance for both brittle and ductile failure modes, with pr V and pr ϑ lower than 1. pr values tend to decrease from F1 to F6. ...
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... application of FRCM at both panel's surfaces can lead to an increment of their inplane strength up to twice the unreinforced one [56]. Figure 12 shows the comparison between inplane force-displacement relationships of strengthened and AB infill panels, using the same symbology of Figure 8. In this case study, the effect of FRCM reinforcement has been numerically implemented by considering a double strength value of inelastic struts associated to each panel, and assuming unchanged cracking and ultimate deformations. ...
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... application also increases the outof-plane strength, up to 400% the original one [57], preventing the expulsion failure mode. Storey shear forces and displacements are plotted in Figure 13 charts for both the X and Y direction. Maximum storey shear forces are 4400 kN and 6400 kN in X and Y directions, respectively, which are about 1000 kN higher than the AB configuration in both directions, with an average increment of 21%. ...
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... ratios, pr, are plotted in Figure 14 charts. RC beams show a good performance for both brittle and ductile failure modes, with pr V and pr ϑ lower than 1, while RC columns exhibit some shear failures at floor F1, with maximum pr V = 1.1. ...
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... time history analysis has been carried out in order to evaluate RP2 structural performance and the obtained results are reported in the following Figures 15 and 16. ...
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... shear forces and displacements are plotted in Figure 15 charts for both X and Y direction. Maximum storey shear forces are about 3000 kN in both directions, that are lower than the AB configuration of about 500 kN in X direction and 2500 kN in Y direction, with an average decrement of 30%. ...
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... ratios, pr, are plotted in Figure 16 charts. RC beams and columns show a good performance for both brittle and ductile failure modes, with pr V and pr ϑ lower than 1. ...
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... on the AB configuration's interstorey drifts and shear forces, FD devices produced by Quaketek [60] have been selected. Figure 17 shows the implemented FDs constitutive model, where an activation force of about 800 kN and a maximum allowable displacement of 94 mm can be observed. Thanks to FDs application, four bracing frames are added to the AB RC frame in both X and Y directions, as schematically represented in Figure 18. ...
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... 17 shows the implemented FDs constitutive model, where an activation force of about 800 kN and a maximum allowable displacement of 94 mm can be observed. Thanks to FDs application, four bracing frames are added to the AB RC frame in both X and Y directions, as schematically represented in Figure 18. Storey shear forces and displacements are plotted in Figure 19 charts for both X and Y direction. ...
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... to FDs application, four bracing frames are added to the AB RC frame in both X and Y directions, as schematically represented in Figure 18. Storey shear forces and displacements are plotted in Figure 19 charts for both X and Y direction. Maximum storey shear forces are 6100 kN and 7100 kN in X and Y directions, respectively, which are about 2000 kN higher than the AB configuration in both directions, with an average increment of 52%. ...
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... RP3, the base isolation technique is applied by using LRBs produced by FipIndustriale [61]. Figure 21 shows the implemented LRBs constitutive model, where an activation force of about 200 kN, a maximum force of 400 kN and a maximum allowable displacement of 333 mm can be observed. Sliding Bearings (SB) that are produced by FipIndustriale [62] are also used at the basement level, together with LRBs, in order to obtain a regular in-plane behavior. ...
Citations
... Important conclusions from this study include: (a) the failure mode of multi-storey piloti frames changes significantly when considering joint degradation compared to assuming rigid beam-column joints; (b) the maximum interstorey drifts of 8-storey frame structures with joint degradation increase in the lower floors and decrease in the upper floors, compared to those simulated with rigid joints; (c) degradation in the joint core area reduces the maximum ductility demands on columns at the base of the multi-storey structure; and (d) the presence of masonry infill improves the seismic performance of piloti structures, especially when the low capacity of exterior joints is taken into account. Grossi et al. (2020) conducted a comparative analysis of four advanced retrofitting techniques applied to typical piloti RC frames designed for gravity loads. The techniques considered include strengthening masonry infilled panels with Fiber Reinforced Cementitious Matrix (FRCM), replacing infilled panels with prefabricated panels, energy dissipation systems, and base isolation systems. ...
Out-of-plane offsets causing wall discontinuities in piloti buildings can generate significant shear forces in the transfer slabs, potentially leading to brittle shear failure and slab collapse during earthquakes. To address this issue, this study investigates the effectiveness of practical shear reinforcement details for reinforced concrete slabs in critical regions influenced by out-of-plane offsets. An experimental program was conducted on ten specimens representing slab-wall connections in piloti buildings. The main test parameters included the shear span-to-depth ratio (a/d) and the configuration of the shear reinforcement. The experimental results found that all the proposed practical shear reinforcement details exhibited favorable performance in strengthening the RC slab-wall connections for a given range of a/d ratios. Notably, these practical details outperformed conventional reinforcement configurations, particularly for slabs with a small a/d ratio of 1.5. Moreover, shear reinforcement details employing T-type units demonstrated comparable performance in reducing crack propagation compared to their U-type-and Z-type counterparts, despite having a smaller effective shear reinforcement area within the shear span. Finally, the shear strengths of the slab-wall connections were evaluated and discussed using current design codes and theoretical models.
... Passive control techniques primarily rely on the yielding or friction properties of metallic materials to dissipate seismic energy [12]. Implementing dissipative devices has proven to be an effective and affordable solution compared to traditional retrofitting methods, preventing damage to structural and non-structural elements [13]. During the last decade, several authors have focused on the seismic rehabilitation of precast RC structures, developing devices that are able to dissipate energy and simultaneously improve the connection between structural elements. ...
Precast RC structures have been widely used in industrial and commercial buildings since the 60 s in the most
developed areas. However, during those decades of economic growth, most buildings were constructed without
seismic design criteria, accounting for gravity loads only. For this reason, this structural typology often faces a
significant seismic risk in earthquake-prone areas due to the lack of effective connection between structural
elements. As a result, the seismic retrofit of precast RC structures is essential to prolong their service life and
mitigate seismic losses. The present work shows the conceptualisation study of an innovative seismic protection
device called Bidirectional Rotational Friction Damper (BRFD) for precast RC structures that behave simultaneously
as a beam-to-column joint and damper. This device unifies the concepts of rotational friction dampers
and a movable plate system, producing a damping effect along two main directions. Furthermore, the device’s
ability to dissipate energy through friction enables it to remain undamaged during multiple seismic events while
maintaining its damping capacity. After defining a simplified analytical model, to evaluate the influence of the
BRFD on a structure’s behaviour during a seismic event, a case study was conducted on a single-story, single-bay
precast reinforced concrete structure made of plane parallel frames, i.e. that lacks secondary frames. Quasi-static
and nonlinear time history analyses were performed to evaluate the BRFD efficacy in reducing seismic forces and
displacements, and an importance analysis was carried out using a multi-criteria decision-making (MCDM)
approach to identify the optimal configuration of the BRFD for the case study. The main results highlight that
introducing the BRFD positively influences the dynamic performance of the structure, producing a significant
reduction of interstorey drift and total base shear and preventing structural and non-structural damage.
... In the context of the seismic rehabilitation of existing buildings, passive control techniques based on energy dissipation devices have proved to be a very efficient solution, being much cheaper if compared to traditional retrofit techniques [1,2], and able to prevent damage to structural elements [3]. Most common and simple dissipation devices are of the hysteretic type, based on yielding or friction properties of metallic materials. ...
... As discussed by Prota et al. (2009), with proper calibration, this model, which was originally developed with rebar bars in mind, can also be used to model smooth rebars often found in existing structures. (Grossi et al. 2020) and the necessary explanations will be explained in this section. Distributed plastic hinge model takes into account distributed plasticity along to all the element cross-sections and the element length. ...
Bingöl, a city in eastern Türkiye, is located at a very close distance to the Karlıova Region which is a junction point
of the North Anatolian Fault Zone and Eastern Anatolian Fault Zone. By bilateral step over of North Anatolian Fault Zone and
Eastern Anatolian Fault Zone each other there occurred NorthWest-SouthEast extended right-lateral and NorthEast-SouthWest
extended left-lateral fault zones. In this paper, a typical school building located in Bingöl Çeltiksuyu was selected as the case
study. Information on the school building and Bingöl Earthquake (2003) have been given in the paper. This study aimed to
determine the fragility curves of the school building according to HAZUS 2022, Turkish Seismic Codes 1998, 2007 and 2018.
These codes have been introduced in terms of damage limits. Incremental dynamic analysis is a parametric analysis method that
has recently emerged in several different forms to estimate more thoroughly structural performance under seismic loads.
Fragility analysis is commonly using to estimate the damage probability of buildings. Incremental Dynamic Analysis have
performed, and 1295 Incremental Dynamic Analysis output was evaluated to obtain fragility curves. 20 different ground motion
records have been selected with magnitudes between 5.6M and 7.6M. Scaling factors of these ground motions were selected
between 0.1g and 2g. Comparison has been made between HAZUS 2022 and Turkish Seismic Codes 1998, 2007 and 2018 in
terms of damage states and how they affected fragility curves. TSC 1998 has more conservative strictions along with TSC 2018
than TSC2007 and HAZUS moderate and extensive damage limits.
... The seismic rehabilitation of existing buildings is a crucial topic for many earthquake-prone countries, and the need of economical but effective retrofit techniques has led researchers to the development of innovative systems [1,2]. Energy dissipation provided by additional devices has proved to be a very efficient and minimally invasive solution if compared to traditional retrofit techniques [3,4], and the most simple and cheap devices are the ones based on friction [1]. For this reason, during the last decades several typologies of Friction Dampers (FDs) have been developed and successfully applied thanks to their versatility, showing the effectiveness of this retrofit technique [5][6][7]. ...
... Grossi et al. [1] presented and discussed four different advanced design solutions for the structural rehabilitation of existing Pilotis RC buildings with a substantial lack of shear and ductility capacity at the first floor. The design solutions are described in detail and were applied to a real building designed only for gravity loads during the 1960s, despite being sited in a high-risk seismic Italian area. ...
Structural rehabilitation has globally become an urgent need due to both widespread construction obsolescence and more demanding requirements from modern construction codes, especially in earthquake-prone areas, where upgrading the existing constructions has become a primary goal [...]
... It is common for existing frames to be retrofitted with RC shear walls [2,8,12] or steel braces [8,13,14]. Moreover, the reduction of seismic demands can be achieved through the use of supplemental damping systems, such as viscous dampers [15,16] or base isolation [2,17,18]. ...
The seismic performance of existing buildings can be improved significantly through the installation of various retrofit technologies. Decision support systems can be used for the selection of an optimal retrofit alternative when several important decision variables (DVs) need to be considered. Typically, the decision-making process considers a range of economic, social and technical aspects that are of interest to decision-makers; however, less or no consideration is given to the environmental impact (EI) of the retrofit alternatives. This study investigates how including the EI of possible retrofit alternatives as an additional DV in a multi-criteria decision making (MCDM) process can affect the choice of the optimal retrofitting scheme for a reinforced concrete school building in Italy. An assessment methodology for determining the life cycle EIs for the case-study structure, based on environmentally extended input-output life cycle analysis, is described. Then, a set of five retrofit alternatives is developed using response estimates from non-linear static analyses and their performance is assessed using non-linear time-history analysis and the PEER-PBEE framework. Several decision assessments are conducted, using the MCDM framework, each considering a subset of 13 possible DVs, including EI, to select an optimal retro-fitting alternative. The results of the MCDM assessment and their implications are discussed in detail. The main conclusions were: (1) in some instances the expected annual EI may be a suitable proxy for the total life cycle EI when used in the MCDM framework; (2) the use of aggregated performance metrics such as the Life Cycle Performance Metric should be carefully considered when the MCDM procedure is used for the decision analysis, and; (3) the most significant factor affecting whether or not the inclusion of EI will affect the choice of optimal alternative is the weights of the DVs assigned by the decision-maker.
... A suitable procedure to select buildings needing structural rehabilitation is out of the scope of the present paper. The authors believe that the proposed numerical approach will be a useful tool for retrofit intervention design [1,2]. Jacketing historical masonry structures with steel-reinforced concrete is among the most conventional techniques for seismic retrofitting. ...
The present paper reports an experimental study coupled with a numerical modelling approach to simulate masonry walls strengthened with textile-reinforced mortar (TRM). This innovative reinforcing technique is based on high-strength fibre grids embedded into inorganic matrices, and it has recently been promoted for the seismic retrofitting of historical masonry buildings. In the experimental campaign presented here, two different commercial TRM systems are applied to single-leaf clay masonry panels. The specimens are then subjected to diagonal compression tests in order to evaluate the effects of TRM on the structural performance. The proposed finite element (FE) model, based on an original multiscale approach, is employed to simulate the diagonal compression tests. The numerical results show a very good agreement with the experimental data, including in terms of failure mode. In particular, the approach reproduces the macroscopic behaviour of the masonry panels as regards the force-displacement response, and it allows for the possibility of simulating bed joint sliding and TRM layer debonding.
This paper presents a numerical investigation into the fire endurance of carbon fiber reinforced polymer (CFRP)-strengthened columns, shielded with fire-resistant materials, in piloti-type reinforced concrete buildings. The strengthened column, equipped with a fire protection system, underwent exposure to the ASTM E119 standard time-temperature curve for a duration of 4 h. To comprehensively evaluate the thermal and structural performance of the strengthened column at elevated temperatures and substantiate the effectiveness of the fire protection system, a fully coupled thermal-stress analysis was conducted. The numerical modeling approach employed in this study was rigorously validated through previous experimental studies in conjunction with adherence to the ACI design guideline, specifically ACI 440.2R-17. Using the validated structural fire model, the thermal and structural behaviors of the RC column with an insulated CFRP strengthening system were investigated based on four key performance criteria: glass transition temperature, ignition temperature of polymer matrix, critical temperature of reinforcing bars, and the design axial load capacity at elevated temperatures. Furthermore, a comparative assessment of fire endurance was performed using diverse fire-resistant materials, including Sprayed Fire-Resistive Material (SFRM) and Sikacrete®-213 F, with insulation thicknesses ranging from 10 to 30 mm, during the 4-hour fire exposure period.
Precast RC structures have been widely used in Italy during past 60 years and mainly adopted to host industrial and commercial activities, as well as school buildings, such as the “Ercole I d’Este” in Ferrara. For these structures, quite common features are poor connections between structural elements, along with limited shear strength and flexural ductility of columns. Many of them were designed for gravity loads only, since past regulations did not imposed earthquake loads application for the whole Italian territory. Recent seismic events have proved how much these structures are prone to premature and fragile collapse, as observed during the 2012 Emilia Earthquakes when they caused several casualties, injured people, and displaced. This study presents the application of Buckling Restrained Braces (BRBs) as advanced retrofit solution for a sustainable upgrading of precast RC structures seismic performances. BRBs are implemented to add significant damping to traditional external seismic steel bracings, and seismic forces are transferred to external bracings thanks to a proper floor and roof reinforcement. Direct displacement-based design is applied to design BRBs, optimizing their sizing and plan position. BRBs effectiveness on the RC precast structure upgrading has been investigated using nonlinear time history analysis. The designed retrofit solution provides a global improvement of the seismic performance of the building to prevent any structural and nonstructural damage with sustainable costs. The major benefit of BRBs application respect to traditional braces is the reduction of external bracing and their foundations which leads to significant savings.
KeywordsSeismic retrofitbuckling-restrained braceRC precast structurenonlinear time history analysisdirect displacement-based design