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Multifunctional properties of shape memory materials in civil engineering applications: A state-of-the-art review
Abstract
Shape memory materials (SMMs) are an important group of intelligent multifunctional materials used in civil engineering applications whose popularity is due to their unique capability to memorize their original shape. After deformation they can return to their initial shape under stimuli, e.g. heat. SMMs are classified into four categories: shape memory alloys (SMAs), magnetic shape memory alloys (MSMAs), shape memory polymers (SMPs), and shape memory ceramics (SMCs). In different situations, these multifunctional materials can be used in actuator systems, structural health-monitoring systems, self-healing applications, etc. The present study provides a comprehensive review of recent developments and applications of SMMs in civil engineering. The advantages and disadvantages of each group are highlighted and practical issues are discussed in detail.
... These abilities are caused by phase transitions between the two crystal structures. Due to these unique characteristics, SMAs have been widely used in various fields, for example, medicine, automotive engineering, aerospace and civil engineering [1]. In civil engineering, numerous scholars have studied the application of SMA since 2000. ...
... In recent years, Fe-SMAs have been widely applied in civil engineering for structural strengthening, particularly in concrete and steel structures. (1) In concrete structures, Fe-SMA can be used for flexural strengthening [14][15][16][17][18][19][20][21][22][23][24][25] and shear strengthening [26,27]. 1) For flexural strengthening, Czaderski et al. [14] studied the feasibility of the Fe-SMA strip in concrete structures and demonstrated that the recovery stress value was 300 MPa. Shahverdi [15], Schranz [16], and Hong [17] investigated the bending capacity of near-surface-mounted (NSM) strengthened beams by Fe-SMA rebars/strips, and Dolatabadi et al. [18,19] conducted relevant numerical simulations. ...
In this study, a new iron-based shape memory alloy (Fe-SMA) plate with a thickness of 3 mm was developed in China, and its mechanical and recovery behavior was experimentally investigated. The influences of various activation temperatures (100 ℃ ~ 480 ℃), prestrain levels (2%, 4%, 6%, 8%, 10%), and initial stresses (50 MPa, 75 MPa, 100 MPa) on the recovery stress were investigated. Stress-temperature curves after secondary activation and recovery stress relaxation were also measured. The experimental results indicated that the Fe-SMA plate exhibited excellent mechanical properties, including an elastic modulus of 162 GPa, yield strength of 512 MPa, ultimate strength of 952 MPa, and ultimate strain of 40.5%. The recovery stresses of the Fe-SMA plates ranged from 191 MPa to 417 MPa. The recovery stress increased with the increase of activation temperature, but the increment decreased gradually. At activation temperatures of 100 ℃ ~ 200 ℃ and 250 ℃ ~ 480 ℃, the recovery stresses of Fe-SMA plates with prestrain levels of 6% and 8% were larger than that of Fe-SMA plates under other prestrain levels. The tested recovery stress relaxation was 10.8% ~ 13.5% after 1500 h. The recovery stress relaxation within the first 24 h and 240 h accounted for 48.7% ~ 56.5% and 78.7% ~ 79.3% of the total stress relaxation in 1500 h, respectively. Based on the test results for the mechanical properties, a modified stress-strain model was proposed for the Fe-SMA plate without prestrain.
... Shape memory alloys (SMAs) are intelligent metallic materials capable of "remembering" their original shapes [25][26][27][28]. SMAs exhibit two distinct macroscopic mechanical properties: shape memory effect (SME) and superelasticity (SE), both of which are induced by phase transitions between austenite and martensite within the material [29,30]. ...
Despite the significant engineering applications of vibration isolation structures, there remain challenges in adjusting low-frequency isolation performance. To tackle this issue, this study proposes a temperature-controlled quasi-zero stiffness vibration isolation structure utilizing NiTi shape memory alloys. The stiffness and vibration isolation performance of the structure can be adjusted by modifying the heat treatment process and temperature variations of the alloy. The vibration isolation system is composed of vertical and horizontal alloy beams, with structural mechanics analysis performed to develop both static and dynamic theoretical models. The study investigates the effects of the heat treatment process on the phase transition characteristics and mechanical properties of nickel-titanium alloys, and analyzes the correlation between the heat treatment parameters of alloy beams and the stiffness performance of vibration isolation structures. By applying temperature variations to the alloy beams, the stiffness and vibration isolation performance of the entire structure can be dynamically adjusted. This research provides theoretical guidance for achieving adjustable vibration isolation performance across low-frequency and wide ranges, offering promising prospects for the application of vibration isolation structures in dynamic environments.
... Compared to Ni-Ti SMAs, iron-based shape memory alloys (Fe-SMAs) possess several advantages, such as stable recovery stress and low cost. In recent years, there has been extensive research on the properties of Fe-SMAs and their applications in civil engineering [18][19][20][21][22][23][24][25][26][27][28]. Dong et al. [29][30][31] proposed a new application method by combining the Fe-SMA bar and the corrugated plastic pipe aiming to apply the Fe-SMA in new structures. ...
To investigate the potential for further enhancing the cracking resistance of thin-walled UHPC by prestressing, the uniaxial tensile and three-point bending experiments for UHPC specimens reinforced with iron-based shape memory alloy (Fe-SMA) wires were conducted. The specimens were placed in an oven and heated to 150 C, 200 C, and 250 C, which was intended to activate the Fe-SMA wires to produce self-prestress. The characteristics of different reinforced methods and heating temperatures were systematically compared. The cracking load and the crack development were recorded using Digital Image Correlation (DIC) techniques. The result shows that at the temperature of 150 C, compared to the dog-bone shaped specimens without reinforcement and the specimens with steel wires, the mean cracking load of specimens with Fe-SMA wires was enhanced by 13.4% and 9.8%, respectively. The study preliminary verified that this method can activate Fe-SMA inside UHPC.
... MSMAs are renowned for their capacity to modify magnetic and other characteristics through phase transitions [11,12]. Embedding MSMA wires into concrete structures offers the opportunity to assess their structural integrity through the use of external magnetic field detection and also provides strength to concrete by providing reinforcement [13]The study suggested that the presence of a crack in a concrete beam produces a stressed area within an embedded MSMA wire. This stressed area can modify the external magnetic flux density in proximity to the stressed region. ...
Currently, the field of structural health monitoring (SHM) is focused on investigating non-destructive evaluation techniques for the identification of damages in concrete structures. Magnetic sensing has particularly gained attention among the innovative non-destructive evaluation techniques. Recently, the embedded magnetic shape memory alloy (MSMA) wire has been introduced for the evaluation of cracks in concrete components through magnetic sensing techniques while providing reinforcement as well. However, the available research in this regard is very scarce. This study has focused on the analyses of parameters affecting the magnetic sensing capability of embedded MSMA wire for crack detection in concrete beams. The response surface methodology (RSM) and artificial neural network (ANN) models have been used to analyse the magnetic sensing parameters for the first time. The models were trained using the experimental data obtained through literature. The models aimed to predict the alteration in magnetic flux created by a concrete beam that has a 1 mm wide embedded MSMA wire after experiencing a fracture or crack. The results showed that the change in magnetic flux was affected by the position of the wire and the position of the crack with respect to the position of the magnet in the concrete beam. RSM optimisation results showed that maximum change in magnetic flux was obtained when the wire was placed at a depth of 17.5 mm from the top surface of the concrete beam, and a crack was present at an axial distance of 8.50 mm from the permanent magnet. The change in magnetic flux was 9.50 % considering the aforementioned parameters. However, the ANN prediction results showed that the optimal wire and crack position were 10 mm and 1.1 mm, respectively. The results suggested that a larger beam requires a larger diameter of MSMA wire or multiple sensors and magnets for crack detection in concrete beams.
... Within SMMs, SMPs have captured considerable interest from academic and industrial sectors due to their remarkable characteristics. These advantages encompass their ability to be engineered for biocompatibility, their ease of manufacturing, their inherently low density, and the capability to tailor their recovery temperature to specific applications [2]. ...
This paper comprehensively investigates the dynamic viscoelastic behavior of shape memory polymer composites (SMPCs) reinforced with different weight percentages of kenaf fiber (KF) ranging from 0%, 5%, 10%, 15%, 20%, 30% and 40%. The dynamic mechanical behavior of these composites was characterized using dynamic mechanical analysis (DMA) over a range of temperatures. The objective was to determine the optimal fiber content of KF as reinforcement in SMPCs, specifically on viscoelastic response, storage modulus, loss modulus, damping and glass transition behaviour. The results revealed a clear correlation between the KF contents and the dynamic mechanical properties of SMPCs. The storage modulus significantly improves at higher KF content, particularly at elevated temperatures. Additionally, a quantitative assessment of coefficient C demonstrates strong interfacial bonding between fibers and the matrix in samples 30KF and 40KF. These samples also exhibit higher loss modulus and lower tan delta values, providing evidence for the efficacy of KF in enhancing composite properties. Moreover, higher KF contents induce a shift in the glass transition temperature, signifying enhanced in fiber-matrix interaction and thermal stability. The Cole-cole further demonstrates that at higher KF content, the sample surpasses Neat SMPU, presenting compelling evidence of improved matrix-fiber bonding. Statistical analysis through one-way analysis of variance (ANOVA) substantiates the statistical significance of the dynamic mechanical properties across the different weight percentages of KF-SMPCs. Based on these findings, 30KF is the optimal fiber content, balancing mechanical enhancement and feasible fabrication. This decision is grounded in challenges encountered at 40KF, where ensuring composite homogeneity becomes complex. This study contributes to the growing body of knowledge on utilization of natural fibers in development of advanced polymer composites while maintaining eco-sustainability.
... The phenomenon of gradual stress increase is attributed to localized stress variations around Ni 4 Ti 3 precipitates within the material. This stress heterogeneity leads to sequential transformations: First, the B2-R transformation occurs, followed by R-B19 ′ , primarily in regions with higher stress near Ni 4 Ti 3 precipitates [27,28]. Simultaneously, a third transformation of R-B19 ′ occurs [23] in regions of lower stress, further from the Ni 4 Ti 3 precipitates. ...
Over the past few decades, there has been a growing trend in designing multifunctional materials and integrating various functions into a single component structure without defects. This research addresses the contemporary demand for integrating multiple functions seamlessly into thermoplastic laminate structures. Focusing on NiTi-based shape memory alloys (SMAs), renowned for their potential in introducing functionalities like strain measurement and shape change, this study explores diverse surface treatments for SMA wires. Techniques such as thermal oxidation, plasma treatment, chemical activation, silanization, and adhesion promoter coatings are investigated. The integration of NiTi SMA into Glass Fiber-Reinforced Polymer (GFRP) laminates is pursued to enable multifunctional properties. The primary objective is to evaluate the influence of these surface treatments on surface characteristics, including roughness, phase changes, and mechanical properties. Microstructural, analytical, and in situ mechanical characterizations are conducted on both raw and treated SMA wires. The subsequent incorporation of SMA wires after characterization into GFRP laminates, utilizing hot-press technology, allows for the determination of interfacial adhesion strength through pull-out tensile tests.
... With the development of intelligent materials, their potential in the field of active control is gradually being explored [25,26]. Shape memory alloy, as an intelligent material, is favored by many scholars and engineers due to its unique properties, shape memory effect (SME) [25,27] and superelastic (SE) behavior [28][29][30]. SMA mainly has two phases: martensite and austenite [31]. Shape memory effect refers to that SMA generates plastic deformation in the martensitic phase and causes martensitic reverse transformation under external stimulation, thereby eliminating residual strain [32]. ...
... Combining the self-healing mechanism of SMA with the pollution barrier technology will make the barrier material even more ductile. This barrier material is more advantageous in facing freeze-thaw, wet/dry cycles and geological (c) After heating healing (Abavisani et al., 2021;Burton et al., 2006) Page 5 of 22 343 ...
Barrier materials are highly susceptible to breakage under various disturbances leading to pollution barrier failure. Therefore, it is necessary to construct self-healing materials for pollution barrier technology. Barrier materials are highly similar in composition to concrete materials. Therefore, the self-healing mechanism of concrete materials and related evaluation methods are described in detail. Based on the existing self-healing materials, the possibility of combining different self-healing mechanisms with barrier materials and the compatibility of self-healing mechanisms with complex polluted environments were analyzed in detail. Barrier self-healing materials not only ensure the long-term effectiveness of pollution barrier technology, but also significantly extend the service life of pollution barrier walls. Therefore, this paper proposes a theoretical support for the self-healing mechanism of barrier materials and points out the key research direction of pollution barrier technology in the future.
... SMAs are a class of smart materials with physical properties similar to structural steel, capable of 'memorising' their shape due to the reversible transitions between its two main phases (i.e., martensite and austenite) caused by a shear lattice distortion mechanism [14]. SMA components in austenitic phase manifest a superelastic (or pseudoelastic) effect, characterised by a flag-shaped stress-strain curve with high load-unload stiffnesses and reduced permanent strains [15]. ...
Inter-module connections (IMCs) play a crucial role in the structural behaviour of steel Modular Building Systems (MBSs) by ensuring the vertical and horizontal load-transfer paths between modules, yet existing designs display limited disassembly opportunities and lack damage control features. This study introduces a novel, hybrid demountable IMC comprising bespoke corner fittings, a resilient high-damping rubber core and a shape-memory alloy (SMA) bolt. Proof-of-concept connection tests have been carried out using validated, continuum finite element analysis (FEA) to determine the mechanical behaviour of the proposed IMC with respect to the main deformation modes expected to occur in the joints of tall steel MBSs under the combined effect of vertical and horizontal loading. Main findings show that both the HDR core and the SMA bolt contribute effectively to the overall hybrid response of the IMC under tension and combined compression and shear loading, preventing the formation of significant plastic damage in the MBS’s corner fittings to facilitate reusability of modules.
... Shape memory alloys (SMAs) are intelligent materials that find widespread application in the fields of aerospace [1], biomedical [2], and civil engineering [3], owing to their unique shape memory effect (SME) and superelasticity (SE). In the field of actuator design, the main principle utilized is SME, which refers to the ability of certain materials to recover a predetermined shape when heated. ...
The functional fatigue behavior of shape memory alloy (SMA) beam actuators is gaining importance as their utilization in engineering applications becomes more widespread. However, research on the functional fatigue behavior of SMA beam actuators under bending conditions is not as extensive as that on SMA wires. In this paper, an experimental study and theoretical analysis of the functional fatigue behavior of SMA beam actuators were conducted. A measuring method for bending deflection and an automatic thermal cyclic test bench was designed. A series of functional fatigue tests were conducted on SMA beam actuators under different bias load conditions and the functional fatigue patterns were obtained. The material damage factor is defined and calculated through specimen tests. By incorporating the damage factor to modify the existing constitutive model, a model considering functional fatigue and tension-compression asymmetry is obtained. Finite element analysis (FEA) is performed based on this modified model to simulate the actuating performance of SMA beam actuators and to compute the deflection at different numbers of cycles. Additionally, a small parameter study on the actuator shape is conducted using FEA. By comparing the FEA results with functional fatigue experimental data, the effectiveness of the modified model is validated, demonstrating its capability to describe functional fatigue and predict actuator lifespan.
... NiTi alloy has excellent performance and is used in fields such as engine heat exchangers, medical heart stents, advanced bearings, and building shock absorbers [1][2][3][4]. Therefore, having a good surface quality is very important. ...
NiTi alloy has a wide range of applications due to its unique superelasticity and shape memory, so it is very important to study NiTi alloy polishing. In this paper, a new method of ultrasonic-assisted electrochemical polishing of NiTi alloy is innovatively proposed, and an ultrasonic electrochemical polishing device is built independently. The effects of ultrasonic amplitude, voltage and temperature on roughness are explored by Box-Behnken experimental design method. The results show that after ultrasonic electrochemical polishing, the surface quality of NiTi alloy is improved. As the temperature increases, the solution viscosity decreases, the ion exchange rate accelerates, and the roughness shows a weak trend of first decreasing and then increasing. With the increase of the interaction between voltage and temperature, the roughness shows a trend of first decreasing and then increasing. This study improves traditional electrochemical polishing methods and introduces ultrasonic energy fields to expand the application of electrochemical polishing, further providing a new approach and laying a foundation for the polishing of NiTi alloys with complex structures in additive manufacturing.
... These changes are triggered by external physical and chemical influences such as temperature, light, pressure, electrical, magnetic, or chemical stimuli. The changes that result fall into a variety of different categories as follows [10]: a. Movement in materials that change form. b. ...
In recent years, many smart materials for architectural applications have been invented. Some smart materials can adapt and interact with the surrounding environment and its variants, whether temperature, humidity, daylight or electric current. Smart material changes its shape without any need for assistance, and it can return to its original state without any significant deformation in shape with the end of the external influence. The invention of smart materials stimulated several architects and facade designers to consider using them in various architectural applications such as sun shading, sun breakers, and windows, significantly impacting the concept and technology of movement in kinetic architecture. The paper attempts to study and analyze some new trendy smart materials and their applications in kinetic architecture based on movement typologies. The results show the ability of these smart materials to develop the movement typologies in the architectural designs to be more adaptive to the environment and users.
... The self-prestressing properties of the iron-based shape memory alloy (Fe-SMA) enable it to strengthen the concrete structure without onsite mechanical tensioning, which is convenient and fast, and have attracted numerous studies [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. Hong et al [34][35][36][37] evaluated the application of Fe-SMA in strengthening concrete structures from the aspects of recovery stress, bond performance, and prestress transfer. ...
The tensile stress caused by the diffusion of the prestress in the post-tensioned anchorage zone will Induce premature cracks at the end anchorage zone of prestressed concrete structures. Indirect steel reinforcements are usually adopted to resist tensile stress. However, too dense indirect reinforcements often have an adverse effect on the casting quality of the concrete. In light of the above, it is proposed in this paper to replace the conventional steel spiral stirrup with the newly developed iron-based shape memory alloy (Fe-SMA) spiral stirrup, which can generate hoop confinement through its shape memory effect (SME). The extra hoop confinement provided by the Fe-SMA spiral stirrup could theoretically improve the cracking resistance of the anchorage zone. A finite element model using ABAQUS was established to simulate the compression performance of a concrete prism with the Fe-SMA spiral stirrup, and the model was verified by theoretical calculation results. The transverse stresses along the tendon path under different hoop prestressing levels in the elastic stage were compared. Moreover, the load-displacement curves and the cracking of the overall anchorage zone were also investigated. The results showed that using the Fe-SMA spiral stirrup can effectively improve the anti-crack performance of the anchorage zone.
... In civil and mechanical engineering SMA based on iron or copper are used as they are cheaper than Nitinol and are, therefore, affordable for large scale applications [36; 37]. The use of SMA in civil engineering is quite novel, as first investigations were carried out in the 1970s while first applications were used in the 1990s and early 2000s [37][38][39][40]. Several publications proposed different iron-based shape memory alloys for the use in applications [36; 37; 39] as these are affordable and reveal a decent shape memory effect. ...
Ultra‐high performance concrete (UHPC) is characterised by a high compressive strength, high durability, and a dense microstructure. The latter causes UHPC to fail in a brittle and sometimes explosive manner. For this reason, UHPC is reinforced with microfibre reinforcement. On the one hand, these lead to increased tensile and bending loads being able to be absorbed, but above all to ductile post‐fracture behaviour. The fibres used are mostly steel fibres.
An essential aspect of the fibre reinforcement is the bond strength between UHPC and metallic fibre. The bond is divided into chemical‐adhesive bond, form bond and friction bond. Depending on the shape, material and surface condition of the fibre, the individual types of bond have different effects on the concrete. To quantify these effects, fibre pull‐out tests are often carried out. These provide information about the bond strength between the fibre and the concrete. However, results of various studies show that the bond strength does not automatically correlate with the actual influence on the resulting tensile and flexural strengths of concrete components.
... Shape memory alloys (SMAs) are known for the programmability of their response to the external stimuli, such as temperature gradient and/or mechanical stress [1], and their properties can also be transferred into many different matrices (e.g., polymers, steels or even concrete) [2,3]. Prominent members of the SMA and smart functional materials families, Ni-Mn-Ga off-stoichiometric Heusler compounds form a subclass of SMAs that respond not only to the change of temperature but also magnetic field [4,5]. ...
... Shape memory materials are materials that once programmed into a temporary form, following an external stimulus, for example thermal, can return to their original configuration [1]. In the last decade, the applications in which they are involved are many: from the robotics sector [2], to the biomedical sector [3,4] and their presence is also evident in the civil engineering sector [5] and textiles [6,7]. Shape memory materials can be either polymeric [8], or metal alloys [9]. ...
The behavior of solid cellular structures in polylactic acid (PLA) manufactured by Fused Deposition Modeling (FDM) is herein investigated. In particular, the manuscript investigates the capability of permanently deformed PLA structures to restore their starting shapes, once a thermal stimulus is applied on them. In this study, a structure called Rototetrachiral was produced, which originates from Rotochiral and Tetrachiral. The latter was tested to verify its mechanical response and its ability to absorb energy when subjected to a compression stress, repeated over several cycles. The experimental results showed a close connection between the structure’s ability to absorb energy and its extent of damage, which gradually increases with the number of cycles. Microscopic analysis shows that the central cells are the most deformed. However, the applied thermal stimulus allows to recover the deformation, ensuring good performance of the structure for a certain number of cycles.
... Shape Memory Alloy (SMA), initially applied in precision and cutting-edge fields such as aerospace, robotics and medicine, has seen rapid development in research and application in civil engineering as material processing techniques and industrial production capabilities have advanced. SMA exhibits excellent superelasticity, generating recovery forces during loading-unloading cycles that facilitate crack closure and deformation recovery in structures [5]. Consequently, superelastic SMA is employed to enhance the self-centering and energy dissipation capabilities of structures, such as in the fabrication of dampers, supports and other energy dissipation and self-centering devices [6][7][8], or directly in strengthening structural components like shear walls and beams [9][10][11]. ...
In order to investigate the effect of fiber end on the bonding mechanical properties between shape memory alloy (SMA) fibers and Engineered Cementitious Composites (ECC), this study designed and fabricated five groups of specimens with variations in SMA fiber end shape, diameter and depth-to-diameter ratio. Direct tensile tests were conducted on these specimens under displacement control. The failure modes, stress–strain curves and various performance indicators were analyzed to evaluate the bonding mechanical properties and the effects of different factors. The results revealed that for straight-end SMA fibers, increasing the diameter and depth-to-diameter ratio both led to a decrease in bonding strength. On the other hand, the N-shaped end provided sufficient anchorage force for SMA fibers, resulting in a maximum pull-out stress of 926.3 MPa and a fiber strength utilization of over 78%. Increasing the fiber diameter enhanced the maximum pull-out stress and maximum anchorage stress for N-shaped-end SMA fibers but reduced the fiber strength utilization. These research findings provide a solid theoretical basis and data support for achieving a synergistic effect between SMA fibers and the ECC matrix.
... The crystal structures of the two SMAs phases are temperaturedependant: austenite is stable at high temperature, while martensite at low temperature [36]. For civil engineering applications, Ni-Ti can be manufactured in austenite phase at a wide range of desirable working temperatures, which enables austenitic Ni-Ti components to manifest the superelastic (or pseudoelastic) effect (SE), characterised by the ability to accommodate large strains (as high as 8-10%) under loading and recover their initial shape when unloaded [37]. Moreover, bespoke attributes such as the ability to dissipate energy through stable cyclic hysteresis, high damping, combined with excellent fatigue and corrosion resistance have fostered the application of Ni-Ti components in passive damage control devices [38,39]. ...
The recent technological advancements achieved in modular construction have accelerated the trend of building taller self-standing steel modular building systems (MBSs), leading to a consensus among researchers regarding the vital role that inter-module connections (IMCs) play in the structural performance of MBSs subjected to extreme lateral loading. However, existing IMCs are typically designed such that the global structural system heavily relies on the hysteresis of the steel framing member, leading to severe sustained damage and costly, impractical retrofitting programmes. To unlock the full “disassembly and reuse” potential of steel MBSs, IMCs can be designed to contribute more effectively to the global damage distribution mechanism, by engaging specific “fuse” components which are easy to replace, improving the reuse prospects of volumetric modules. In this regard, the present study proposes a novel, hybrid IMC using custom corner fittings, a high-damping rubber (HDR) core and a shape-memory alloy (SMA) bolt. Calibrated and validated material models using data from experimental material characterisation tests have facilitated the full characterisation of the hybrid mechanical response, determining the deformation modes, stress states, hysteresis loops and mechanical parameters. The parametric FEA included the variation of bolt preload, endplate thickness, axial load magnitude and the vertical layout of the HDR core. The study represents a preliminary, proof-of-concept investigation, showcasing the favourable cyclic performance of the proposed IMC under the main deformation modes expected in tall self-standing MBSs during lateral loading. Due to the effective contribution of each component to the combined hybrid response, the connection succeeds in preventing the formation of significant plastic damage in the MBS’s corner fittings to facilitate reusability of modules.
... Fatigue phenomena in an aggressive environment are the most common causes of structural and electrical power line cable failure (Xue et al., 2020). Wires are exposed to a combination of mechanical loads, vibration, and self-heating in service that creates cyclic stress and brings failure over time (Abavisani et al., 2021). Besides, the relative actions between wires, sides and plastic encapsulation produce fatigue and corrosion under stress, known as the fretting phenomena (Guan et al., 2022). ...
Fatigue failure of wires is a frequent issue that evolves over time as a result of utilizing the profile under variable stress and temperature. In this article, an innovative study makes it possible to propose a protective tool for metal profiles against fatigue using shape memory alloys (SMA). Smart actuators like SMA are able to push back sudden stresses above the elastic limit, therefore, are characterized by high resistance to fatigue and even against corrosion due to their strong thermomechanical coupling. Besides, the study provides the results necessary to add a layer based on the shape memory tube to protect the important connectors for industrial systems and automotive industries. The conductivity of electrical current in various electronic devices depends on the copper material, which is good at conducting electricity and heat but weak against mechanical forces and hence easily susceptible to fatigue. Thereby, the elastic regime of copper is different from that of SMA, and in order to adapt the properties of two materials, a mathematical study can describe the behaviour of two combined systems is important for the analysis of the cyclic effect and for adapting the proposed actuator in wiring technology. Therefore, the study shows the great potential of the proposed SMA tube with its superelastic behaviour to increase the predicted lifespan of metallic wires against corrosion and fatigue. The lifetime of the conduction system with the protective SMA is increased remarkably and can reach up to 10 5 cycles under the action of the stress of an amplitude of 550 MPa, the finite element simulation shows that the system of SMA combined with a 4 mm wire undergoing significant stress up to 490 MPa that can reach a deformation of 7% and return to the initial state without residual deformation. The simulation's results look at the evolution of stress, strain, fatigue lifetimes, and anticipated damage, and they match the experimental results of SMA tube properties rather well. Consequently, the verification of the proposed model confirms the improvement in the lifespan of studied wires compared to wires without SMA encapsulation.
... Investigations on the employment of SMA as a strengthening element of concrete members have hence been intensified in the last years [34][35][36][37][38]. A comprehensive overview of the application of SMA in civil infrastructures, including steel, concrete, and timber structures, is offered by Zareie et al. [39], for strengthening and repair applications for concrete structures in [40], and in a review from the perspective of multifunctional properties of the alloy by Abavisani et al. [41]. Moreover, SMA are employed in both steel and concrete beam-column joints. ...
Beam–column joints are the critical section of many reinforced concrete (RC) structure types in which any failure could lead to the collapse of the entire structure. This paper attempts to employ a superelastic shape memory alloy plate as an innovative and adaptive external strengthening element to rehabilitate existing concrete beam–column joints and enhance the structure’s performance.
An experimentally investigated beam–column joint is used as the case study, and it is investigated numerically to validate the effects of an innovative strengthening technique based on shape memory alloys. The results show that the proposed technique could increase the joint’s stiffness and reduce the risk of overall failure. A particular innovation in the proposed method is associated with the novel material itself but also with the fact that the increased potential costs of using special alloys
are counteracted by its potential to produce these elements in an optimised industrially produced fastened plate. This fits-all construction product further allows a rapid and minimally invasive strengthening technique. Moreover, to achieve this, the plate is adaptively designed against random critical load combinations through probabilistic damage prediction.
Keywords: shape memory alloy; reinforced concrete; beam–column joints; probabilistic damage analysis; non-linear finite elements; ansys APDL; MATLAB
... For example, SMA elements can be embedded into the laminated composite structures to create smart sensing and actuating devices. Hence, nowadays, the SMA-based hybrid laminated composite structures are widely used for innovative applications in various areas including aerospace [1], automotive [2] and civil engineering [3]. ...
This paper presents a coupled thermoelastic finite element formulation for static and dynamic analysis of composite laminated plates with embedded active shape memory alloy (SMA) wires, which accounts for both the phase transformation and the nonlinearity effects of SMA wires. The equations of motion are obtained by using Hamilton's principle and first-order shear deformation theory (FSDT). Furthermore, based on Brinson's one-dimensional phase transformation con-stitutive law, a novel coupled thermoelastic finite element model that enables analysis of the SMA hybrid composite (SMAHC) plate is developed. The accuracy and efficiency of the developed computational model for analysis of SMAHC plates are reinforced by comparing theoretical predictions with data available from the literature. The results of the numerical examples also show the ability of the proposed model to predict the thermal-mechanical behavior of SMAHC plates in accordance with SMA's hysteresis behavior. In addition, based on the proposed model, the influence of temperature as well as SMA volume fraction, pre-strain value, boundary condition and layup sequence on the static bending and free vibration behavior of the SMAHC plates is investigated in detail. The results of parametric analysis show that the variations of both static deflection and natural frequency of the SMAHC plate over temperature exhibit a nonmonotonic behavior.
... The self-prestressing properties of the iron-based shape memory alloy (Fe-SMA) enable it to strengthen the concrete structure without onsite mechanical tensioning, which is convenient and fast, and have attracted numerous studies [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. Hong et al [34][35][36][37] evaluated the application of Fe-SMA in strengthening concrete structures from the aspects of recovery stress, bond performance, and prestress transfer. ...
Iron-based shape memory alloys (Fe-SMAs) have been widely studied as a new type of prestressing material for near-surface mounted (NSM) or external strengthening, and have been used in numerous strengthening projects in Europe. However, Fe-SMAs have not been widely used in new structures due to their uncertain bond properties after high-temperature activation. Therefore, a new type of application in new structures is proposed, which is composed of Fe-SMA bars, plastic corrugated pipes and high-temperature-resistant cement mortar. The bond properties between Fe-SMA bars and cement mortar after resistive heating were investigated through pull-out tests. The influence of different heating temperatures and heating times on the bond properties was analyzed. It was shown that when the temperature of the inner Fe-SMA bars was 150 °C–350 °C, the surface temperature of the plastic corrugated pipes was only 35 °C–65 °C, which indicated that the activation process would not transfer excessive heat to the concrete outside the plastic corrugated pipes. With the increase of the heating temperature, the ultimate bond strength, bond stiffness, residual bond stress, and energy dissipation all gradually decreased. Compared with the specimens at ambient temperature, the specimens could still maintain a high ultimate bond strength with only approximately 10% loss after being heated to 200 °C and cooled down. When the activation temperature was below 300 °C, the more serious bond degradation could be observed with the longer heating time. However, when the temperature exceeded 300 °C, the influence of heating time was negligible. In addition, prediction models for the ultimate bond strength and the bond-slip curves were proposed, which could provide references for subsequent studies.
Capacitance-based measurement, which enables self-sensing without the need for any conductive additives, is very advantageous for the construction and building sector as it can be applied both in existing and newly constructed structures. In this study, the most effective electrode configuration has been investigated to detect the most effective self-sensing ability. Capacitive self-sensing measurements were conducted in a 10.3-kPa to 41.2-kPa stress regime during loading and subsequent unloading at progressively increasing stress levels. Aluminum foil acting as the electrode was attached to the mortar plate using dielectric film. The capacitance was measured by an LCR meter. The most effective configuration for self-sensing was determined by varying the area of the coplanar electrodes and the distances between them. The sensing effectiveness increased with decreasing electrode width, such that the highest effectiveness was obtained when the width was 1.5 cm. Moreover, the effectiveness increased with decreasing inter-electrode distance, such that the highest effectiveness was obtained when the distance is 10 cm. With the optimum electrode design, the highest sensing effectiveness of 4.4% was reached. So, the most effective capacitive self-sensing is achieved by positioning the electrodes closest to the area where the load is applied and keeping the electrode area low.
This article presents a study of the use of composite materials in strengthening building structures. Materials consisting of two or more components or phases are called composite. Now modern composite materials open up new opportunities for design in all areas of production. The construction industry is no exception. Laminates, canvases, nets, rebars and ropes made of high-strength fibers of various origins are among the most widely used in construction at the moment. The main components of any composite are high-strength fibers that absorb the load, and a stabilizing matrix that serves to transfer forces to the fibers. The following types of high-strength fibers are used in composites: glass fibers, carbon fibers, organic fibers, silicon-carbon, aluminum-silicon fibers, and others. With the help of composite reinforcement, it is possible to effectively strengthen normal and inclined sections of reinforced concrete structures.
This paper conducted a full-scale experiment on a PCCP with an inner diameter of 1400 mm and a length of
6000 mm. A finite element model was established on the basis of this experiment, and the influence of different
recovery stresses, Fe-SMA bar diameters, and material types on the strengthening effect was investigated. The
simulation results indicated a notable enhancement in the strengthening effect upon employing Fe-SMA bars
with recovery stresses of 0 MPa, 175 MPa, 330 MPa, and 382 MPa, respectively. With the increased recovery
stress, the micro-cracking pressure enhanced 33.8 %, 51.5 %, 72.1 %, and 80.9 % and the visible cracking
pressure enhanced 12 %, 24.8 %, 31.6 %, and 33.1 %, respectively, compared to the non-strengthened PCCP.
Finally, this paper proposed a design concept for a short-duration, micro excavation PCCP strengthening method
based on the self-prestressing of the Fe-SMA.
Smart materials are upcoming in many industries due to their unique properties and wide range of applicability. These materials have the potential to transform traditional engineering practices by enabling the development of more efficient, adaptive, and responsive systems. However, smart materials are characterized by nonlinear behaviour and complex constitutive models, posing challenges in modelling and simulation. Therefore, understanding their mechanical properties is crucial for model-based design. This review aims for advancements in numerically implementing various smart materials, especially focusing on their nonlinear deformation behaviours. Different mechanisms and functionalities, classification, constitutive models and applications of smart materials were analyzed. In addition, different numerical approaches for modelling across scales were investigated. This review also explored the strategies and implementations for mechanically intelligent structures using smart materials. In conclusion, the potential model-based design methodology for the multiple smart material-based structures is proposed, which provides guidance for the future development of mechanically intelligent structures in industrial applications.
Monitoring of the corrosion process of alloys in real conditions often results in extensive data, which is characterized by complex interdependence, but by a large degree of mutual deviation. First of all, the large dispersion of the obtained results makes it very difficult to draw accurate conclusions about the real influence of the tested parameters on the corrosion behavior of alloys. On the other hand, in many cases, the high interdependence between the corrosion factors can also greatly burden the analyzed system and thus make it significantly difficult to recognize the main influence. Multivariate analysis, especially the principal component analysis, is becoming increasingly popular in processing of this type of data, due to its ability to recognize and eliminate redundant data. The aim of this study was to examine the possibility of using multivariate analysis methods in the processing of the corrosion test results obtained under real conditions. Based on the obtained results, it can be concluded that used multivariate method in combination with energy dispersive spectrometer analysis can be successfully used to identify the most important corrosion factors (type of corrosion environment, exposure time and technological production processes), as well as their influence on the degradation of the tested TiNi alloys under the given conditions.
In this paper, the influence of different material trademarks, mass ratios, the melt mass‐flow rate (MMFR) and molecular weights (MW), mold and injection temperatures, Al2O3 powder and lignin on the shape memory properties of PLA/PCL SMP material (PPSM) were then analyzed in detail by different characteristic methods. Besides, three promising applications (Origami metamaterials and variable‐stiffness grippers) are provided utilizing the PPSM doped with Al2O3/lignin. Eventually, a compensating strategy was discussed to improve the final configuration of the SMP after multi‐cycles. The shape memory recovery ratios could be improved by increasing the MMFR of PLA and the MW of PCL. The addition of 2 g‐Al2O3 could shorten the recovery time, while the addition of 2 g‐lignin could increase the thermal‐recovery force and mechanical performance. The shape memory rate under 20 g weights, initial peak forces at room and high temperatures of the origami metamaterials could reach 57%, 2027.29 N and 17.49 N, respectively. The tensile force of banding rebars could reach 150.29 N, which is promising to apply into the construction field.
The reinforcement binding in the construction field has recently been moving from manual to automation. However, the current binding device powered by electrical motors is complex and unwieldy. This paper proposes a method for reinforcement binding under thermal driving utilizing the thermally induced shape memory characteristic of shape memory polymer composite support with integrated structure and function. The method involves manufacturing support memory binding shape, programming to temporary shape, and reheating to complete binding. Supports reinforced with ceramic powder and glass fiber are manufactured using molds. The tensile test shows a positive correlation between the maximum tensile force of support and the weight fraction of reinforcing materials. The 6.93% weight fraction glass fiber reinforced support achieves the highest tensile force among all supports, at least 39% higher than the maximum tensile force of existing wire binding. All supports require 9 s to complete binding at 60°C, while it only takes 6 s to increase the heating temperature to 80°C. This article presents the potential of thermally driven shape memory polymer composite support for reinforcement binding for the first time.
Crystalline admixture (CA) has garnered attention as a promising alternative self-healing agent for cementitious composites. This paper aims to provide a compressive review on the effects of CA on the self-healing behaviours and durability properties of cementitious composites. CA is in powder form, consisting of Portland cement and special chemicals as self-healing stimulants. Since the powder-form CA was directly mixed with the cementitious mixture, CA addition has no significant impact on the properties of fresh concrete but enhances the compressive strength of CA-cementitious composites. Furthermore, self-healing is activated by moisture, resulting in the pro-duction of calcium-based self-healing products. In terms of crack closure efficacy, specimens cured under wet/dry cycle demonstrated a higher crack closure ratio than those cured under water immersion or air exposure. CA-cementitious specimens cured in chloride solution exhibited the best healing recovery. However, reduced mechanical recoveries are observed in specimens exposed to freeze–thaw cycles and those in chloride solution, while better mechanical recoveries are found in specimens exposed to wet/dry cycles. Overall, CA can reduce the sorptivity, permeability, chloride penetration, and the depth of sodium ions penetration, offering favourable protection for cementitious composites. Although some durability properties of CA-cementitious composites have been explored, further studies are required to investigate potential effects on shrinkage, ingress of aggressive ions, carbonation, and alkali-silica reaction (ASR). The application of CA in cementitious composites could be considered as a cost-effective approach for inducing self-healing products, given its affordable and straightforward construction process.
Shape memory polymers (SMPs) are polymeric smart materials, a class of stimuli‐responsive polymers that can return to their initial shape from a programmed temporary shape under the application of external stimuli, such as light, heat, magnetism, and electricity. Because of these unique features, SMPs can find applications in many fields, like aerospace, biomedical devices, flexible electronics, soft robotics, shape memory arrays, and 4D printing. The comparatively low density, low cost, easy biodegradability, and biocompatibility make SMPs a better candidate for shape memory applications. Among them, thermo‐responsive SMPs can revert to their permanent shape depending on a temperature greater than their polymer transition temperature. Thermo‐responsive SMPs combine semi‐crystalline or elastomeric polymers with improved mechanical and electrical properties. Integrating nanofillers into the polymer elastomer matrices can further enhance these properties, forming shape‐memory polymer nanocomposites (SMPNCs). This review focuses on the basics, design, and classifications of thermo‐responsive SMPs and the characteristics of elastomers and blends of polymers used. Incorporating various nanofillers to get SMPNCs to have improved properties over SMPs is also presented. The importance of T g (glass transition temperature) and T m (melting temperature) based SMPs and SMPNCs, various elastomers used, and the methods for preparation like solution casting, melt compounding, in situ polymerization, and their possible future applications are also discussed.
Fe-Ga alloys are regarded as promising new magnetostrictive materials owing to their excellent magnetic and mechanical properties. However, the currently developed polycrystalline Fe-Ga alloys always have randomly oriented crystal and magnetic domain structures, resulting in poor magnetostriction. In this study, a processing route comprising laser-beam powder bed fusion (PBF-LB) followed by annealing with stress (AS) was proposed for the preparation of bulk polycrystalline Fe81Ga19 alloys. Specifically, the properties of PBF-LB Fe81Ga19 alloys under different annealing stresses (50 MPa, 100 MPa, 150 MPa) were investigated in this study. Owing to the high solidification rate and temperature gradient, the PBF-LB Fe81Ga19 alloys exhibited a < 001 > preferred orientation and maze-like magnetic domains along the building direction. And the subsequent AS process motivated the rotation of magnetic domains with increasing stress owing to the magnetoelastic effect. Specifically, the magnetic domains transformed from the original maze-like pattern in the PBF-LB alloys to a well-aligned striped pattern after AS at 50 MPa, and to a nearly 90° striped pattern at 100 MPa, but evolved into irregular pattern at 150 MPa. As a result, the PBF-LB Fe81Ga19 alloys after AS at 100 MPa showed a maximal magnetostriction of ∼82 ppm, which was 39% higher than that of the alloy without annealing. Moreover, the prepared Fe81Ga19 alloys exhibited soft ferromagnetic behavior characterized by low coercivity, low hysteresis loss, and high permeability. In addition, the AS process led to an increase in the number of high-angle grain boundaries and a decrease in the dislocation density, which may account for the enhanced compressive yield strength of up to 540 MPa. These findings suggest that PBF-LB followed by AS may be an effective method to improve the magnetostriction of polycrystalline Fe-Ga alloys.
Water contamination has turned into a critical global concern that menaces the entire biosphere and has a notable effect on the lives of living beings and humans. As a proper and environmentally friendly solution, visible-light photocatalysis technology has been offered for water contamination removal. There is a strong interest in the design of the efficient catalytic materials that are photoactive with the aid of visible light. Herein, to fabricate a highly efficient photocatalyst for removal of organic pollution in water, a facile and swift sonochemical route employed for creation of the spindle shaped PbWO4 nanostructure with the aid of an environmentally friendly capping agent (maltose) for the first time. To optimize the efficiency, dimension and structure of lead tungstate, various effective factors such as time, dose of precursors, power of ultrasound waves and kind of capping agents were altered. The attributes of PbWO4 samples were examined with the aid of diverse identification techniques. The produced lead tungstate samples in role of visible-light photocatalyst were applied to remove organic pollution in water. The kinds of pollutants, dose and type of catalyst were examined as notable factors in the capability to eliminate contaminants. Very favorable catalytic yield and durability were demonstrated by spindle-shaped PbWO4 nanostructure (produced at power of 60 W for 10 min and with usage of maltose). Usage of ultrasonic irradiation could bring to improvement of catalytic yield of PbWO4 to 93%. Overall, the outcomes could introduce the spindle-shaped PbWO4 nanostructure as an efficient substance for eliminating water contamination under visible light.
Here, we offer an easy and eco-friendly sonochemical pathway to fabricate Nd2Zr2O7 nanostructures and nanocomposites with the help of Morus nigra extract as a new kind of capping agent. For the first time, the performance of Nd2Zr2O7-based ceramic nanostructure materials has been compared upon NOx abatement. Diverse kinds of techniques have been employed to specify purity and check the attributes of the fabricated Nd2Zr2O7-based nanostructurs by Morus nigra extract. Outcomes revealed the successful fabrication of Nd2Zr2O7 nanostructures and nanocomposites applying Morus nigra extract through sonochemical pathway. All nanostructured samples have been fabricated through ultrasonic probe with power of 60 W (18 KHz). Further, the fabricated Nd2Zr2O7-based ceramic nanostructure materials can be applied as potential nanocatalysts with appropriate performance for propane-SCR-NOx, since the conversion of NOx to N2 for the best sample (Nd2Zr2O7-ZrO2 nanocomposite) was 70%. In addition, in case of Nd2Zr2O7-ZrO2 nanocomposite, the outlet quantity of CO as an unfavorable and unavoidable product was lower than the rest.
In this work, the magnetization response of FeMnAlNi superelastic shape memory alloys (SMAs) is investigated under stress. Wires with a diameter of 0.5 mm were subjected to repeated abnormal grain growth heat treatments in order to obtain bamboo structured oligocrystalline grains that are necessary for superelasticity. Solution heat treated wires were aged at 200ºC for 3 h to strengthen the austenite matrix. Tensile cyclic tests were performed at room temperature until failure, while the magnetization response of the wires was monitored using a hall sensor during loading and unloading in each cycle. It is observed that after each cycle, overall magnetization of the alloy decreases once the irrecoverable strain is introduced after large deformations and magnetization of the sample is inversely correlated with the irrecoverable strain. The findings of this work show that the magnetic shift in Fe-SMAs under deformation can be used a health monitoring tool in next generation structures to detect large deformations and cracks.
The conventional semi-active variable damping (VD) device can only dissipate the vibration energy, which inherently limits its performance in vibration control. This paper proposes a novel semi-active inerter concept and develops a prototype with magnetorheological (MR) dampers, which can store the vibration energy in a flywheel and then release it to suppress vibration. The new idea is inspired by a variable inertance (VI) device, which has a VD device and a passive inerter in serial, and a passive mechanical motion rectifier (MMR), which can convert the reciprocating input into a unidirectional output. The controllable MMR (CMMR) applies two VD devices to replace the two one-way roller clutches in the MMR. By equipping the CMMR, the semi-active inerter gets more controllability than the original VI device because it can switch the torque and motion transmitting routes between the device terminals and the flywheel in it. The frequency-domain analysis validates the versatile of the semi-active inerter, which can work in VD and VI modes. The test results of the semi-active MR inerter prototype are used to identify the device parameters, which are applied for the control simulation. The semi-active MR inerter in CMMR mode has the best torque tracking performance with a given test condition, and it has a 20.13% improvement than in the VD mode. Then, a seat suspension with the semi-active MR inerter is applied to validate the effectiveness of the device in vibration control. The results show that the vibration reduction of the seat suspension in the CMMR mode is 39.3% higher than in the VD mode, which indicates a significant improvement of ride comfort. The new concept of the semi-active device has excellent potential in vibration control and is promising in practical applications.
Introducing high-performance compounds for hydrogen sorption is of interest because of their advantages for substantial applications such as energy storage. Here, the role of copper addition on hydrogen storage capability and Coulombic efficiency of CeO2 nanostructure (fabricated by an easy and surfactant-free sonochemical pathway) was examined, for the first time. Nanostructured oxides were fabricated with loading various percentages of copper (4 wt% and 40 wt%) inside CeO2. Nanostructured copper-ceria binary oxides were checked by diverse analyses. The hydrogen storage performance as well as Coulombic efficiency of the nanostructured copper-ceria binary oxides and the net CeO2 were checked through chronopotentiometry charge−discharge pathway in the alkaline medium. The outcomes exhibited that the hydrogen storage capacity of CeO2 nanostructure could be enhanced with adding the proper dosage of copper as a beneficial low-cost solution. Self-assembled copper-doped CeO2 hierarchical nanostructures could display the most appropriate performance than the net CeO2 and nanostructured Cu2O–CeO2. The discharge capacity for the self-assembled copper-doped CeO2 hierarchical nanostructures (fabricated by adding 4 wt% copper) could rise to 5070 mAh/g at 22nd cycle. Appropriate porosity, special architecture and unique morphology as well as convenient surface area of the self-assembled copper-doped CeO2 hierarchical nanostructures render they can be very beneficial compounds in the energy storage.
Shape memory alloys have been used in developing self-centering steel moment connections. This article presents a numerical study aiming at evaluating the cyclic response sensitivity and limit states of extended endplate steel connections with shape memory alloy bolts. Three-dimensional finite element models are developed and validated against a recent experimental study. Using a statistical design-of-experiment method, the effects of 21 design factors and their interactions on the cyclic response of shape memory alloy connections are assessed. The sensitivity of six response parameters is studied. In addition, four limit states for shape memory alloy connections are discussed, including beam local buckling, bolt excessive axial strain, endplate yielding, and column flange yielding. Results show that endplate thickness, shape memory alloy bolt diameter, beam web slenderness ratio, and shape memory alloy maximum transformation strain are the most influential factors. Furthermore, endplate yielding is found to be the governing limit state in almost 80% of the analyzed connections, whereas shape memory alloy bolt excessive strain and column flange yielding are observed in less than 20% and 5% of the connections, respectively. Beam local buckling is not governing in the analyzed shape memory alloy connections designed as per the AISC 358-16 and AISC 341-16 seismic design requirements for extended endplate connections and highly ductile members.
Hard magnetic particle–based magnetorheological elastomers are novel magnetoactive materials in which, unlike the soft particle–based magnetorheological elastomers, the particles provide magnetic poles inside the elastomeric medium. Therefore, the stiffness of the hard magnetic particle–based magnetorheological elastomers can be increased or decreased by applying the magnetic field in the same or opposite direction as the magnetic poles, respectively. In the present work, the viscoelastic properties of hard magnetic particle–based magnetorheological elastomers operating in shear mode have been experimentally characterized. For this purpose, hard magnetic particle–based magnetorheological elastomers with 15% volume fraction of NdFeB magnetic particles have been fabricated and then tested under oscillatory shear motion advanced rotational magneto-rheometer to investigate their viscoelastic behavior under varying excitation frequency and magnetic flux density. The influence of the shear strain amplitude and driving frequency is examined under various levels of applied magnetic field ranging from −0.2 to 1.0 T. Finally, a field-dependent phenomenological model has been proposed to predict the variation of storage and loss moduli of hard magnetic particle–based magnetorheological elastomers under varying excitation frequency and applied magnetic flux density. The results show that the proposed model can accurately predict the viscoelastic behavior of hard magnetic particle–based magnetorheological elastomers under various working conditions.
Since the first publications related to microstructured optical fibers (MOFs), the development of optical fiber sensors (OFS) based on them has attracted the interest of many research groups because of the market niches that can take advantage of their specific features. Due to their unique structure based on a certain distribution of air holes, MOFs are especially useful for sensing applications: on one hand, the increased coupling of guided modes into the cladding or the holes enhances significantly the interaction with sensing films deposited there; on the other hand, MOF air holes enhance the direct interaction between the light and the analytes that get into in these cavities. Consequently, the sensitivity when detecting liquids, gasses or volatile organic compounds (VOCs) is significantly improved. This paper is focused on the reported sensors that have been developed with MOFs which are applied to detection of gases and VOCs, highlighting the advantages that this type of fiber offers.
There are crack interfaces between self-healing agent and cement matrix in smart encapsulation-based self-healing concrete, whose mechanical properties significantly affects the load capacity recovery of crack-healed concrete. In this study, both experimental and numerical investigations were conducted on the crack-healed concrete under uniaxial tension to investigate the interface bonding behaviours and the self-healing agent distribution on the crack surface. The results show that the bonding behaviour of the crack interface depends on the content of healing agent and mechanical properties of the crack surface. However, it is still difficult to accurately understand their effects on the bonding behaviour by experimental investigation due to the high brittleness of the crack interface and the discrepancy of self-healing concrete. Therefore, based on the experimental results, a novel numerical model of the interface between self-healing agent and cement matrix was developed to investigate effects of aggregates, pores and interface properties on the bonding behaviour of crack interface by the cohesive surface technique (CS). Parametric analysis was also performed on the bonding behaviours and a method was proposed for assessing the load capacity of crack-healed concrete. Based on the experimental and numerical investigations on the healing agent-concrete crack interface in the smart encapsulation-based self-healing concrete, this novel numericla methods can be used to assess the recovery efficiency and performance of smart self-healing concrete structure.
To find a low-cost and flexibly adaptive building design and construction method in the field of sustainable architecture, the authors attempted to propose a user-fabricable 3D-printed kinetic shading device that is selectively actuatable by a switch between a geared DC motor and a thermomechanical shape memory alloy (SMA) actuator. This approach leverages additive manufacturing, SMA, and origami to suggest a lightweight, motorless, and silently operable kinetic building module with compact actuation parts. User-customization is prioritized in its manufacturing, installation, and operation: the device is made by 3D-printed thermoplastic components and is self-supportively installable. User-engaged operation is considered by involving an app-based remote control, along with sensor-integrated automation. The results of responsive building performance simulation and mockup tests demonstrate that the thermo-responsive building module enables control of solar radiation and light, reducing room temperature dynamically. The study findings speak to the limitations and potential of material-based actuation for adaptive building technologies.
This study proposes a new type of self-centering damper equipped with novel buckling-restrained superelastic shape memory alloy (SMA) bars. The new solution aims to address some critical issues related to degradation and loss of superelasticity observed in existing tension-only SMA-based self-centering devices, and in addition, to encourage enhanced material utilization efficiency. The cyclic tension-compression behavior of individual SMA bars is experimentally studied first, and subsequently, two proof-of-concept self-centering dampers are manufactured and tested. A simple yet effective numerical model capturing the flag-shaped response of the dampers is then established, and a preliminary system-level analysis is finally conducted to demonstrate the effectiveness of the proposed damper in structural seismic control. The individual SMA bar specimens show asymmetrical flag-shaped hysteretic responses with satisfactory self-centering capability and moderate energy dissipation. Through a specially designed configuration, the proposed damper shows desirable symmetrical and stable hysteretic behavior, and maintains excellent self-centering capability at 6% bar strain. The system-level dynamic analysis indicates that the dampers, as a means of retrofitting, could effectively reduce both the peak and residual inter-story drift ratios of a six-story steel frame. In particular, the mean residual inter-story drift ratio is reduced from over 0.5% to below 0.2% under the maximum considered earthquake, implying elimination of necessary structural realignment even after strong earthquakes.
Expanding the use of smart braced frames to govern the seismic response of structures by providing ductility and elasticity has been hampered and delayed by cost indexes. The braces in frames comprise two segments of expensive shape memory alloys (SMAs) and high-strength steel with high stiffness. These smart materials can reduce seismic damage by providing stiffness, yielding, and phase shifting. In this study, the length of the SMA segments in three- and six-story frames (applied either at all floors or as part of a dual system) was increased to determine the optimal length at a constant period. Performance levels and fragility curves were obtained to evaluate the seismic behavior of the optimized frame. The response modification factor determined based on the static pushover, incremental nonlinear dynamic analysis, and linear dynamic analysis suggests the ductility and over-strength of the optimized frame. The probability of being in or exceeding each damage state was determined with a Monte Carlo analysis and was acceptable and in accordance with previous deterministic analysis results.
This paper describes a simple and environmentally friendly route to develop Dy2Sn2O7 nanostructures with the aid of Ficus carica extract as naturally available fuel, for the first time. In this investigation, we found that shape, purity and dimension of Dy2Sn2O7 could be controlled with varying the determinative factors, the quantity of Ficus carica extract and temperature. The varied techniques have been employed to denote the production of Dy2Sn2O7 and examine its features. We applied diverse structures of Dy2Sn2O7 (fabricated with Ficus carica extract) as visible-light-sensitive photocatalyst for destruction of Acid Violet 7 and crystal violet, for the first time. The fabricated Dy2Sn2O7 with the aid of 2 ml of Ficus carica extract was capable of illustrating a great efficiency to destruct target pollutants. Our findings offer that the as-fabricated Dy2Sn2O7 can be beneficially applied as novel kind of visible-light-sensitive photocatalyst for efficient removal and destruction of organic contaminants in water.
The conductive polymer was introduced to crack surfaces in geopolymers to enable piezo-resistivity. In combination with crack morphology characterization and the piezo-resistive test, the functionalized geopolymer was found to achieve a high sensitivity (with ΔR/R0 /Δε equals to 376.9 for loading and 513.3 for unloading) to both small external stress (less than 2 MPa) and wide range of strains (up to 1700 με). This piezo-resistive behavior can be well described by a coupled mechanical-conductive contact mechanism. A new way to enable the self-sensing function of materials utilizing their existing micro-features was successfully proposed and validated.
Cyclic tests have been conducted on five shape memory alloy (SMA) rings, i.e. single superelastic ring (SE), single martensitic SMA ring (MA), two superelastic SMA rings (SE–SE), two martensitic SMA rings (MA–MA), and martensitic–superelastic SMA rings (MA–SE). Experimental results show that while the single SMA ring systems in this study showed better symmetrical behaviors than those in a previous study, the dual ring systems show perfectly symmetrical behaviors. The use of martensitic SMA could increase the damping ratios of the ring systems while the use of superelastic SMA could enhance the self-centering capacity. In addition to experimental studies, a numerical model of the superelastic SMA ring systems was also developed using ANSYS software. The verification of experimental results showed that the analytical results are acceptable. Furthermore, to examine the effect of SMA ring thickness on the symmetrical behavior of the single SMA systems, a thickness ratio and a hardening stiffness ratio (HSR) are introduced. The thickness ratio is the ratio between the thickness and outer diameter of the rings, while the HSR is the ratio between the stiffnesses in hardening phase of the ring in pulling action and that in pushing action. The analysis results obtained through ANSYS demonstrate that an increase in the thickness ratio leads to a decrease in the stiffness ratio. Therefore, the ring could behave symmetrically when the thickness of the ring reaches a critical value. However, due to the p-delta effect when large displacement is applied, unsymmetrical behavior still occurs. Thus, to ensure symmetrical behavior, it is recommended to use dual SMA ring systems or 2 rings in symmetrical structures.
In this brief review, an introduction of the underlying mechanisms for the shape memory effect (SME) and various shape memory phenomena in polymers is presented first. After that, a summary of typical applications in sensors based on either heating or wetting activated shape recovery using largely commercial engineering polymers, which are programmed by means of in-plane pre-deformation (load applied in the length/width direction) or out-of-plane pre-deformation (load applied in the thickness direction), is presented. As demonstrated by a number of examples, many low-cost engineering polymers are well suited to, for instance, anti-counterfeit and over-heating/wetting monitoring applications via visual sensation and/or tactual sensation, and many existing technologies and products (e.g., holography, 3D printing, nano-imprinting, electro-spinning, lenticular lens, Fresnel lens, QR/bar code, Moiré pattern, FRID, structural coloring, etc.) can be integrated with the shape memory feature.
The present paper deals with the retrofitting of unreinforced masonry (URM) buildings, subjected to in-plane shear and out of-plane loading when struck by an earthquake. After an introductive comparison between some of the latest punctual and continuous active retrofitting methods, the authors focused on the two most effective active continuous techniques, the CAM (Active Confinement of Masonry) system and the Φ system, which also improve the box-type behavior of buildings. These two retrofitting systems allow increasing both the static and dynamic load-bearing capacity of masonry buildings. Nevertheless, information on how they actually modify the stress field in static conditions is lacking and sometimes questionable in the literature. Therefore, the authors performed a static analysis in the plane of Mohr/Coulomb, with the dual intent to clarify which of the two is preferable under static conditions and whether the models currently used to design the retrofitting systems are fully adequate.
In the field of structural health monitoring (SHM), innovative methods of non-destructive evaluation (NDE) are currently being investigated with the purpose of providing prognostic information toward safer, longer lasting structures. Therefore, it is desirable to integrate NDE techniques with existing structural reinforcement techniques for in situ measurement capability, increasing service life. Magnetic shape memory alloys (MSMAs) offer the potential for NDE via magnetic sensing, while further offering the multi-functionality of crack closing and structural reinforcement. The current research proposes a novel SHM approach for concrete structures using embedded MSMAs for magnetic sensing, and investigates the properties of such a system.
Since the mid-1980’s, sensors and actuators have been combined with composite materials in order to enhance and increase the functionalities of the resulting products. These innovative devices are called intelligent, adaptive or smart structures. Their main applications are related but not limited to vibration control, structural health monitoring, shape control and energy harvesting. One possible way of developing these devices is to embed the smart materials inside the structure. In this case, the main challenge is the way of embedding the smart material during the manufacturing process. This review presents the key elements of the manufacturing process, provides an overview of the techniques developed to embed the bulk piezoelectric transducers in the composite and details the achievements made with them. In conclusion, some guidelines for futures researches and developments are proposed
Deployable mechanical systems such as space solar panels rely on the intricate stowage of passive modules, and sophisticated deployment using a network of motorized actuators. As a result, a significant portion of the stowed mass and volume are occupied by these support systems. An autonomous solar panel array deployed using the inherent material behavior remains elusive. In this work, we develop an autonomous self-deploying solar panel array that is programmed to activate in response to changes in the surrounding temperature. We study an elastic "flasher" origami sheet embedded in a circle of scissor mechanisms, both printed with shape memory polymers. The scissor mechanisms are optimized to provide the maximum expansion ratio while delivering the necessary force for deployment. The origami sheet is also optimized to carry the maximum number of solar panels given space constraints. We show how the folding of the "flasher" origami exhibits a bifurcation behavior resulting in either a cone or disk shape both numerically and in experiments. A folding strategy is devised to avoid the undesired cone shape. The resulting design is entirely 3D printed, achieves an expansion ratio of 1000% in under 40 seconds, and shows excellent agreement with simulation prediction both in the stowed and deployed configurations.
This study proposed a new type of the shape memory alloy (SMA) bending bars with a new clamping machine and investigated their bending and cyclic behavior subjected to pushing and pulling actions through experimental works. The aim was to characterize the self-centering and damping capacity of the SMA bending bars to develop self-centering and damping devices and evaluate their efficiency in seismic and dynamic applications. For this aim, two types of SMAs were considered: (1) superelastic SMA (SE SMA) and (2) martensite SMA (MA SMA). First, the bending tests were performed on single SE SMA and MA SMA bars and their corresponding bending behaviors were illustrated in the form of force–displacement curves. Results showed that the MA SMA bar provided higher energy dissipation capacity while the SE SMA could provide a better displacement recovery. Thereafter, the bending behaviors of multiple bars with various combinations of SMA bars, namely, double SE SMA (SS), SE SMA-MA SMA-SE SMA (SMS), and MA-SE-MA (MSM) were investigated. Results showed that MSM provided the highest energy dissipation capacity among all while the SMS showed a better structural performance considering a combination of damping and self-centering capacities. Then, to enhance the displacement recovery and energy dissipation capacity of SMA bars, the single SE SMA bar, and SMS were annealed. Results showed that the annealing enhanced the structural performance, but no perfect displacement recovery was still obtained.
An experimental program was conducted to investigate the performance of large-scale reinforced concrete beams strengthened with near-surface-mounted iron-based shape memory alloy (Fe-SMA) strips. Shape memory alloys are a unique class of alloys with the ability to undergo large deformations and return to their original shape through stress removal by unloading or heating. Four beams were tested in total, including a control beam and three beams strengthened with near-surface-mounted Fe-SMA strips. One beam was strengthened with five nonactivated strips and two beams were strengthened with five and seven activated Fe-SMA strips, respectively. The results revealed the effectiveness of the strengthening technique in enhancing the flexural performance of the strengthened beams at the service and ultimate load conditions. Furthermore, the strengthened beams failed in a ductile failure mode by crushing of concrete after yielding of the steel reinforcements and the Fe-SMA strips, similarly to the behavior of an under-reinforced concrete beam. The performance of the strengthened beams was compared with similar beams strengthened with prestressed near-surface-mounted carbon-fiber-polymer (CFRP) bars with comparable prestressing forces. The comparison revealed the superiority of the near-surface-mounted Fe-SMA in maintaining the ductile behavior of the beams compared with the brittle failure of near-surface-mounted CFRP-strengthened beams.
Driven by a need to reduce repair costs and downtime in structures following a major earthquake, self-centering systems have been introduced. Post-tensioned high strength steel strands have shown promising results in providing self-centering capability in steel frames, where the beams are compressed to columns. This study aims at investigating the feasibility of using reduced length of steel and shape memory alloy strands in steel beam–column connections. Through finite element modeling, the study first evaluates the effect of using short-length regular post-tensioned strands in steel connections. The results show higher strength, stiffness, and energy dissipation capacity for connections with shorter length regular post-tensioned strands. The moment capacity and energy absorption capacity of a post-tensioned beam–column connection with one-third strand length were 105% and 114% higher than those of with full-length strands, respectively. However, residual drifts increased from 4 to 39 mm. To avoid loss in the re-centering capability of such connections due to yielding/failing of post-tensioned steel strands, the application of shape memory alloy and hybrid strands are proposed. The results show that shorter length shape memory alloy strands are effective in regaining self-centering and dissipating higher amount of energy compared to the full-length steel strands.
Metallic structures, in various industrial fields such as transport and aerospace, are mostly replaced by composite structures having less weight and good strength. There is also a need of intensification of the operational dynamic environment with high durability requirements. So a smart composite structure is required that can manifest its functions according to environmental changes. One method of producing smart composite structures is to embed shape memory alloys in composite structures. Shape memory alloys (SMAs) have significant mechanical and thermodynamic properties and are available in very small diameters less than 0.2mm. These SMAs are embedded into composites for obtaining smart composites having tunable properties, active abilities, damping capacity and self-healing properties. Shape memory alloys are available in different shapes as wires, sheets, foils, strips, etc. For smart composites, mostly SMA embedded are in wire shape. Different techniques are used for embedding SMA wires in composites. SMA wires can be embedded between layers of laminates of composites, or embedded directly as reinforcement in matrix and can be woven into fabrics and used as a reinforcement. This paper reviews the different techniques of embedding SMA wires in composite structures, their pros and cons and their applications.
Shape memory polymers (SMPs) have attracted significant attention from both industrial and academic researchers, due to their useful and fascinating functionality. One of the most common and studied external stimuli for SMPs is temperature; other stimuli include electric fields, light, magnetic fields, water, and irradiation. Solutions for SMPs have also been extensively studied in the past decade. In this research, we review, consolidate, and report the major efforts and findings documented in the SMP literature, according to different external stimuli. The corresponding mechanisms, constitutive models, and properties (i.e., mechanical, electrical, optical, shape, etc.) of the SMPs in response to different stimulus methods are then reviewed. Next, this research presents and categorizes up-to-date studies on the application of SMPs in dynamic building structures and components. Following this, we discuss the need for studying SMPs in terms of kinetic building applications, especially about building energy saving purposes, and review recent two-way SMPs and their potential for use in such applications. This review covers a number of current advances in SMPs, with a view towards applications in kinetic building engineering.
As an increasing amount of waste glass is produced every year, recycling glass in manufacturing concrete shows economic and environmental benefits. Recently, glass has been used as one of the ingredients to prepare high-performance fiber-reinforced cementitious composites (HPFRCCs), such as ultra-high-performance concrete and strain-hardening cementitious composite, featuring high mechanical properties and long-term durability. While the use of glass may reduce the material cost, however, fundamental knowledge on the effects of glass on the key material properties (e.g., fresh properties, hardened properties, durability) and the underlying mechanisms is still lacking. This study aims to clarify the roles of glass on the key properties, elucidate the fundamental mechanisms, and point out viable strategies to improve the key properties of HPFRCCs incorporating glass. To this end, the paper reviews existing studies on using glass in preparing HPFRCCs and discusses possible methods to develop HPFRCCs with glass. While there are different types of glass, this review focuses on soda-lime glass, which is representative among all types of glass. Finally, a life cycle analysis is performed to evaluate the effect of using glass on reducing the cost, CO2 emission, and energy consumption. This review is expected to advance the fundamental knowledge of HPFRCC and promote further research and applications of HPFRCCs incorporating glass.
This paper presents the investigation on the adoption of reaction powder concrete (RPC) concept in geopolymer concrete (GPC) technology to develop ultra high performance concrete (UHPC). Ultra high performance geopolymer concrete (UHPGPC) was developed by completely eliminating Portland cement (PC) with industrial by-products such as ground granulated blast furnace slag (GGBFS) and silica fume (SF) activated with sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) solution. The fresh (flow) and mechanical (compressive strength) properties of the mixes with varying replacement level of GGBFS with silica fume, river sand with quartz powder and the inclusion of steel fibres were investigated. The results infer that the inclusion of silica fume, quartz powder and steel fibres has a momentous role on the strength development of the UHPGPC mixes. Additionally, statistical analysis has been carried out by design of experiments using response surface methodology. The ecological parameters were also assessed with the aid of embodied energy and carbon dioxide emission and the results were compared. From the results, it has been inferred that the analytical results were well correlated with the experimental results and the ecological parameters were also less compared to the cement concrete mixes and terms it to be sustainable production.
This study explores an instrumentation strategy using distributed fiber optic sensors to measure strain and temperature through the concrete volume in large-scale structures. Single-mode optical fibers were deployed in three 12.8 m long steel and concrete composite floor specimens tested under mechanical or combined mechanical and fire loading. The concrete slab in each specimen was instrumented with five strain and temperature fiber optic sensors along the centerline of the slab to determine the variation of the measurands through the depth of the concrete. Two additional fiber optic temperature sensors were arranged in a zigzag pattern at mid-depth in the concrete to map the horizontal spatial temperature distribution across each slab. Pulse pre-pump Brillouin optical time domain analysis (PPP-BOTDA) was used to determine strains and temperatures at thousands of locations at time intervals of a few minutes. Comparisons with co-located strain gauges and theoretical calculations indicate good agreement in overall spatial distribution along the length of the beam tested at ambient temperature, while the fiber optic sensors additionally capture strain fluctuations associated with local geometric variations in the specimen. Strain measurements with the distributed fiber optic sensors at elevated temperatures were unsuccessful. Comparisons with co-located thermocouples show that while the increased spatial resolution provides new insights about temperature phenomena, challenges for local temperature measurements were encountered during this first attempt at application to large-scale specimens.
This study aims to clarify the possibility and advantages of producing an Ultra-High Performance Concrete (UHPC) with ultra-low cement content. The UHPC matrix is designed on the basis of the improved Andreasen and Andersen particle packing model (A&A), and then up to 73% (wt.) of cement clinker is replaced by inactive fillers. After that, the effects of large quantity of inactive fillers on UHPC fresh and hardened behaviors are investigated. The experimental results indicate that the reduction of binder content is beneficial for improving the UHPC workability and decreasing its cracking risk. However, when the added cement clinker amount is reduced to about 245 kg/m³ concrete, the compressive strength, durability and pore structure of UHPC deteriorate greatly. Hence, to guarantee the mechanical capacity and sustainable development of UHPC simultaneously, the modified A&A model should be used to design a dense meso-skeleton, while the minimum cement clinker amount can be reduced to about 280 kg/m³ concrete. Additionally, the hydration kinetics and microstructure development of the newly designed UHPC are correspondingly analyzed and discussed.
In this study, the cooperative working mechanism of high-strength reinforcement and ultra-high performance concrete (UHPC) was investigated. Five UHPC columns were tested under reversed loading, including three UHPC columns reinforced with high-strength steel, one UHPC column reinforced with normal-strength steel and one UHPC column reinforce with normal-strength steel and confined by carbon fiber reinforced polymer (CFRP) sheet. The results show that all the columns failed in bending mode. High-strength reinforcement can restrain UHPC effectively and improve the initial stiffness, ductility and bearing capacity of the test columns. The larger stirrup spacing can result in earlier cracking and lower the bearing capacity of the test column. The CFRP sheet can provide effective confinement for the UHPC, which can improve the yield and ultimate displacement of the test columns. However, it has little contribution to the bearing capacity. A flexural model has been developed for the analysis of UHPC bending members, and the results from the model are in good agreement with the experiment data.
The fabrication of carbon fibre-reinforced polymer (CFRP)-based shape memory alloy hybrid composite (SMAHC) beams is highly challenging because conductive carbon fibres alter the electrical characteristics of the beams when driven by an electrical current. Here, we propose and fabricate a CFRP-based SMAHC beam with embedded SMA actuators using the electrical insulation methods. We firstly implemented a self-sensing-based deflection control of the CFRP-based SMAHC beam for unit-step and sinusoidal wave targets using its resistance as a feedback signal for estimating self-sensed deflection. The results reveal that the deflection was well controlled; however, the responses were slightly delayed. Therefore, in our future studies, we will concentrate on overcoming this response delay. Nevertheless, we found that the proposed SMAHC beam is highly feasible and can form the basis for future self-sensing-based controllable CFRP composite morphing structures.
In this article, wave propagation of the sandwich composite beam with tunable electro-rheological (ER) fluid core is investigated. The sandwich composite beam is made of three layers consisting of the basic layer, ER fluid core, and the limiter layer. ER fluid core embedded withindoors the basic and limiter layers. The upper and lower layers are constructed of the elastic materials. Hamilton’s principle is utilized for deriving the governing equations of motion. Using an analytical solution, the wave frequency and the phase velocity can be gathered by solving eigenvalue problem. Moreover, the effect of different parameters such as electric field, core-to-top layer thickness ratio, and thickness of ER core is investigated on the wave dispersion characteristics.
Shape Memory Alloys (SMAs) are a new generation of smart materials with the capability of recovering their predefined shape after experiencing a large strain. This is mainly due to the shape memory effects and the superelasticity of SMA. These properties make SMA an excellent alternative to be used in passive, semi-active, and active control systems in civil engineering applications. This paper presents a comprehensive review of the recent developments in the applications of SMA in civil infrastructures, including, steel, concrete, and timber structures. This review reveals the significance of SMA in civil infrastructures particularly, the enhancement of structural behavior and energy dissipation of external excitation, particularly seismic loads. This enhancement is pronounced under loading-unloading process without residual deformation.
The stability and integrity of structures under indeterminant external loadings, particularly earthquakes, is a vital issue for the design and safe operation of marine and offshore structures. Over the past decades, many structural control systems, such as viscous-based systems, have been developed and embedded in marine and offshore structures, particularly oil platforms to maintain the stability and mitigate the seismic hazards. Rapid improvement in intelligent materials, including shape memory alloys (SMAs) and Magnetorheological fluid (MRF), have led to the design and development of efficient structural control elements. The present work aims to establish a framework for the structural control element in which the controllability of magnetorheological fluid and su-perelasticity effect of shape memory alloy have been combined to generate a new structural control element with an ability to dissipate a significant amount of energy while controlling the inter-element displacement in marine structures. The dynamic responses of a simplified 2DOF structure equipped with structural control elements have been conducted using the Open System for Earthquake Engineering Simulation (OpenSees). A comparison between the present SMA-MRF-based and the viscous-based systems has been performed. IIt is seen that the activated SMA-MRF-based control system in a wide range of the loading frequency spectrum decreases the maximum inter-story displacements of the frame as well as drift ratios. A comparison between the most common stability control element and the present system for seismic conditions has been conducted.
Several confinement methods using concrete casing, steel jacketing, and wrapping with Fibre Reinforced Polymer (FRP) sheets are widely implemented to enhance the strength and ductility of reinforced concrete (RC) columns. Recently, smart materials such as Shape Memory Alloys (SMA) are utilized for repair and strengthening of RC columns. The SMA’s exhibit unique thermo-mechanical properties such as shape memory effect (SME) that enables the material to achieve high recovery stress (up to 600 MPa) and strain (up to 8%). Recent findings in the literature show the SME and high recovery stress of the SMA wires used to confine concrete columns significantly enhanced the strength and ductility performance of concrete. Realizing the potential of the SMA-confinement technique, this paper aims to present an analytical model to describe the behaviour of SMA-confined RC columns subjected to uni-axial compressive loads. Experimental data are compared against theoretically predicted results to validate the proposed analytical model. Results show the proposed analytical model predictions are in good agreement with the experimentally observed axial compressive response of SMA-confined RC columns.
Structural integrity and ensuring the stability of steel frame structures, including marine and coastal structures, are the main challenges for designers in civil infrastructures, particularly in oil platforms, subjected to tough periodic and non-periodic environmental loading conditions. Variable loadings with different amplitudes and frequencies may lead to the stability of steel structures loss. In order to keep the stability of the steel structures and prevent possible damages, reliable yet efficient structural control systems are in demand. Conventional structural control systems need significant activation energy and/or in-depth users knowledge to be effective. Most recently, smart materials and systems, notably shape memory alloy (SMA) and magnetorheological fluid (MRF), are considered to replace with the conventional systems. In this study, the SMA-MRF based structural control systems are installed in a simplified marine structure to investigate the frequency responses of the structure subjected to three scaled ground motions. Three structural parameters including the root-mean-square (RMS), the peak displacement, and particularly the frequency analysis are studied. The results show remarkable enhancement in structural behavior equipped with the SMA-MRF based system.
Wind and ocean waves highly influence the performance and functionality of structures, requiring an efficient control element. The structural behavior of one of the most recent structural control elements, namely shape memory alloys (SMA)-based control element, under cyclic loadings of oceans waves, has been investigated. Shape memory alloys are one of the attractive smart materials with the ability to return to the initial shape after experiencing large deformation. Experimental tests have been conducted to study the effects of cyclic loads on several specimens of the SMA wires. The SMA wires are being used in the SMA-based structural control system to dissipate the energy of external loading and enhance the structural dynamic behavior of offshore structures. It is realized that the number of loading cycles and the amount of the initial displacement reduce the strain recovery of the SMA-based element
This book introduces readers to the fundamental properties and practical applications of shape memory alloys (SMAs) from the perspective of seismic engineering. It objectively discusses the superiority of this novel class of materials, which could potentially overcome the limitations of conventional seismic control technologies. The results, vividly presented in the form of tables and figures, are demonstrated with rigorous experimental verifications, supplemented by comprehensive numerical and analytical investigations.
The book allows readers to gain an in-depth understanding of the working mechanisms of various SMA-based structural devices and members, including beam-to-column connections, dampers, and braces, while also providing them with a broader vision of next-generation, performance-based seismic design for novel adaptive structural systems. Helping to bridge the gap between material science and structural engineering, it also sheds light on the potential of commercializing SMA products in the construction industry. The cutting-edge research highlighted here provides technical incentives for design professionals, contractors, and building officials to use high-performance and smart materials in structural design, helping them stay at the forefront of construction technology.
Supported by recent studies, a crack interior to the host material will cause an especially strong stress concentration and thus can be detected by monitoring or sensing the localized changes in the magnetic properties of the particles in metallic composites. Using finite element analysis calibrated from the experiments, this work investigates the effects of material properties and thickness of the particle/matrix interphase on the phase transformation response of embedded sensory particles in the vicinity of a crack existing in the host matrix. Depending on the interphase elastic and cohesive properties, its thickness, and the operational temperature, which is known to delay or promote martensitic transformation, it is found that interphase damage may occur at stress levels lower than that needed to initiate phase transformation in MSMA particles. Such a response would mitigate the degree to which the particle transforms and reduces particle sensitivity. The effect of particle position relative to the crack tip on interphase damage and particle transformation response is studied via the full factorial design of experiments. To assess the true feasibility of the technique, the average change in magnetic permeability in the vicinity of the particle given constant applied magnetic and applied stress fields is evaluated.
Shape memory alloys (SMAs) have been introduced into structural engineering in recent years. This paper presents research results about developing a new methodology to actively strengthen reinforced concrete (RC) beams by low-cost iron-based SMA strips (Fe-SMA). These strips can transversally prestress, or confine, the cross-section of beams thanks to the shape memory effect of Fe-SMA, without having to apply prestressing force. Activation of strips is carried out by heating them up to 160ºC and then cooling them. An experimental campaign was carried out at two levels: characterization of Fe-SMA strips, and the practical application of the strengthening technique on small-scale beams without internal stirrups. The retrofitted beams with activated strips failed by bending, and the appearance of shear cracks was clearly delayed. Meanwhile, the reference beams failed due to shear.
Reversible shape-memory polymers (RSMPs) show great potential in actuating applications due to its repeatability among many other advantages. Indeed, in many cases, multiresponsive RSMPs are more expected, and the strategy to introduce functional fillers without deteriorating the reversible deformation performance is of great importance. Here, a facile strategy to balance the electro, photothermal performance, and molecular chain mobility is reported. Segregated conductive networks of carbon nanotube (S-CNT) are constructed in poly(ethylene-co-octene) (POE) matrix at a relatively low filler loading, which renders the composite good electrical, photothermal and actuating properties. A low percolation threshold of 0.25 vol % is achieved. The electrical conductivity is up to 0.046 S·cm-1 for the POE/S-CNT composites with 2 vol % CNT, and the absorption of light (760 nm) is above 90%. These characteristics guarantee that the actuator can be driven at low voltage (≤ 36 V) and suitable light intensity (250 mW·cm-2) with a good actuating performance. An electric gripper and a light-active crawling robot demonstrate the potential applications in multiresponsive robots. This work introduces a facile strategy to fabricate multiresponsive RSMPs by designing CNT network structures in polymer composites, and holds great potential to enlarge the applications of RSMPs in many areas including artificial muscles and bionic robots.
This chapter proceeds with discussions of the application of SMA elements in self-centring bracing members in framed structures. First, the existing solutions for self-centring braces are briefly introduced, and the potential limitations are also outlined. A series of newly proposed braces, employing SMA wires, tendons or ring springs, are subsequently discussed in detail. The main focus of this chapter is on the design principle, working mechanism, and fundamental mechanical behaviour of the kernel devices for the braces. Some technical issues such as the manufacturing process and annealing scheme are particularly addressed for the devices equipped with SMA ring spring systems.
Facing the serious pollution caused by non-degradable plastic waste, environmentally benign materials from sustainable polymers have attracted tremendous research interest. Specially, functional fibers with good mechanical properties, shape memory behavior and biodegradability have been required in the fields of smart textiles, sensors and intelligent robot. Here, a new solvent, 4.5 wt% LiOH/7.5 wt% KOH/11.5 wt% urea aqueous solution, was developed to prepare stable cellulose/chitosan composite solution. Subsequently, cellulose/chitosan composite (CLS) fibers were spun successfully from the mixture solution on a lab-scale spinning machine. The CLS fibers exhibited good mechanical properties with tensile strength of 3.2 cN/dtex in the dry state and 2.9 cN/dtex in the wet state, as a result of the combination of good miscibility between two components and their nanofiber self-assembly driven by self-aggregation force through hydrogen bonding interactions. Interestingly, the CLS fibers showed a two-switch shape memory behaviors under water and acid stimulations. By changing the external stimulation, the strong self-aggregation force between cellulose and chitosan could be destroyed partly and then restructured to fix and recover, resulting in a designed shape. This work provided a new method for fabricating high strength and functional fiber in industry, which will promote the development of smart textiles.
Through embedding functional materials into structural components, smart composites offer an alternative to structural health monitoring (SHM). The present work focuses on the development of a new kind of composite with metamagnetic shape memory alloy (MMSMA) particles as the sensory particle reinforcements. The premise of this approach is that sensory particles can experience martensitic transformation (MT) in the presence of the crack tip stress field, emitting acoustic signals and changing their magnetic state upon the transformation, which can be exploited using acoustic and/or magnetic sensors to detect the crack location. The composite fabrication consisted of the consolidation of pure Al and Ni 43 Co 7 Mn 39 Sn 11 MMSMA powders through spark plasma sintering at 400 °C and 560 °C. Consolidation at 400 °C yielded a porous composite. Consolidation at 560 °C yielded a highly dense composite with a diffusion region between the particles and matrix consisting of Al-Mn-Ni rich and Sn-Mn rich zones. Thermomagnetic testing of this composite displayed a similar response to the standalone Ni 43 Co 7 Mn 39 Sn 11 powder indicating that the particles can still transform after the composite fabrication. Fatigue crack testing of the composite revealed particles in the presence of cracks undergoing MT. This demonstrates the feasibility of the sensory magnetic particle approach as a potential new SHM technique, however, the interface should be further engineered to optimize the load transfer from matrix to the particles.
This review paper discusses the potentials and applicability of cheaply processed Cu and Fe based shape memory alloys for vibration control in civil structures. Evidences available show that most devastations from seismic activities are accentuated by the consequent tremor induced collapse of buildings and civil structures. Accordingly, measures for controlling the threats of structural vibrations has been a huge concern globally. NiTi based shape memory alloys which possess excellent damping properties have been the focus in recent times for the design of vibration control systems. However, the prohibitive material costs and complexity of processing has raised concerns on the practicality of their commercial utilization in buildings and civil structures compared to other vibration control approaches. From this background, this review paper advances the use of Cu and Fe based SMAs by exploratory examination of the extent of their use in buildings and civil structures as vibration control devices/systems. Based on the findings from the literatures analyzed, it is concluded that Cu and Fe based SMAs are technically useful, simply implementable and sustainable SMAs for consideration as structural vibration control systems/devices in buildings and civil structures.
In order to counteract summer overheating, the demand for cooling energy in buildings has rapidly increased in recent years. Well-designed external shading systems can minimize the need for cooling energy by up to 75 %. For this purpose, a thermosensitive actuator based on the thermal shape memory effect has been developed to regulate a shading system according to climate conditions. At the same time, user´s intervention is partially allowed, e.g. over the winter to provided demand-controlled glare shield, since overheat protection is not required.
Shape memory alloys (SMAs) show great potential in seismic applications because of their appealing superelastic feature and good energy dissipation capacity. The tensile behavior of SMA wires and bars has been extensively studied over the past decades. However, little attention has been paid to their compressive properties under cyclic loading. Thus, this paper presents a systematic experimental study on the cyclic behavior of superelastic SMA bars with buckling-restrained devices (BRDs) when subjected to tension–compression cycles. The detailed design of BRD is described first. The material properties such as “yield-like” strength, peak strength, self-centering capability, and energy dissipation of typical interest in seismic applications are evaluated with varying strain amplitudes, strain rates, and loading protocols. Test results show that satisfactory and stable flag-shaped hysteretic loops without any strength degradation are obtained in multiple loading cycles under cyclic tension–compression loading. Moreover, the SMA bars exhibit remarkable self-centering capability that is nearly independent of strain rate and loading protocol.