The use of shape memory alloys (SMAs) in civil structures attracted the attention of researchers worldwide. This interest is due the unique properties of SMAs, the shape memory effect (SME) and pseudoelasticity. Other desirable attributes for SMA include biocompatibility, high specific strength, wear resistance, anti-fatigue characteristics, and high yield strength. These beneficial qualities allow for a wide range of applications ranging from aerospace field to the medical and civil engineering fields. To intelligently utilize shape memory alloys and widen their application potential, certain characteristics including the heat activation and heat transfer mechanisms must be thoroughly understood. Such understanding would allow the development and optimization of systems utilizing SMA. Hence, this paper presents a state-of-the-art review about shape memory alloys with specific focus on the heat activation mechanisms and the heat transfer modes.

Reinforced Concrete (RC) core walls are widely used to resist lateral loads because of their high flexural and torsional stiffnesses. Their seismic performance parameters, including residual displacement, floor acceleration, and residual in-plane rotation, were examined by many researchers. However, reports from previous earthquakes have highlighted the difficulties of repairs addressing their residual displacements and/or rotations. This paper addresses this problem by investigating the influence of self-centering superelastic shape memory alloy (SMA) bars on the seismic performance parameters of RC core walls. A case study building is analyzed, considering both steel and SMA reinforcement, for unidirectional and bidirectional seismic excitations. Different mass eccentricities are assumed. SMA RC core walls are found to have significantly reduced floor accelerations, residual displacements, and residual in-plane rotations as compared to steel RC core walls.

In modular construction, individual modules are constructed at a controlled industrial environment before being transported to site. They are then connected horizontally and vertically to form a structure. The vertical connections can be achieved by welding or bolting the columns of stacked modules. This study investigates the seismic performance of modular steel-braced frames (MSBFs) connected vertically using superelastic shape memory alloy (SMA) bolts. The study also identifies the required locations of SMA connections, in a typical MSBF, to optimize its seismic performance in terms of maximum inter-story drift (MID), maximum residual inter-story residual drift (MRID), and damage scheme.

Corrosion is a major factor in the deterioration of reinforced concrete (RC) structures. To mitigate this problem, steel bars can be replaced with glass-fiber-reinforced-polymer (GFRP) bars. However, the lack of ductility of GFRP-RC elements has prevented their use in many structural applications, especially in seismic areas. Superelastic shape memory alloy (SMA) bars have been proposed to be used in seismic areas because of their self-centering characteristics. Also, they have the added advantage of being corrosion resistant. This paper examines the combined use of SMA and GFRP bars to achieve ductile self-centering and corrosion-free elements. The first challenge for such a proposal relates to designing concrete frames, reinforced with SMA and GFRP bars, that have adequate lateral performance in terms of initial stiffness, ductility, and strength. A comprehensive parametric study is conducted to better understand the structural behavior of concrete elements reinforced with SMA and/or GFRP bars. Results from the study are utilized to develop design equations that allow designing an SMA/GFRP RC section to replace a steel RC section, while maintaining lateral strength, stiffness, and ductility. To examine the adequacy of the developed equations, a six-storey concrete frame is designed, and its lateral performance is examined using pushover analysis.

Trend of using smart structures, which can adjust when exposed to severe unexpected loading, is increasing. One of the methods to achieve such structures relies on smart materials. For example, replacing conventional steel reinforcing bars in Reinforced Concrete (RC) structures with superelastic Shape Memory Alloy (SMA) bars significantly reduces the residual deformations caused by post-yielding behaviour. This paper provides in-depth understanding of the flexural behaviour of SMA RC beams. A sectional analysis method, which predicts the flexural behaviour of SMA RC beams during both loading and unloading stages, is adopted and validated using available experimental data. An extensive parametric study is then carried out to investigate the effect of different geometrical properties. Recommendations for the optimum amount and length of SMA bars are drawn based on results of this study.

Pre-1970s designed and built reinforced concrete frame structures are considered unsafe when subjected to seismic loads. Insufficient anchorage of the beam reinforcement in the beam-column joints of these structures is considered a main deficiency. Newly built frame structures are seismically designed for safety, where high inelastic deformations can occur under moderate to strong earthquakes. Minimizing these inelastic deformations makes the structure repairable. One way to minimize these residual deformations is by using smart materials such as superelastic shape memory alloys (SMAs). In this paper, the seismic performance of RC frames retrofitted using external superelastic SMA bars is investigated and compared to the behaviour of a regular steel RC frame structure. Nonlinear time history analysis is performed for a six storey RC frame structure located in a high seismic region. After performing the analysis, two retrofitted frames are assumed and analyzed at the load intensities causing failure of the steel RC frame. The performance of the retrofitted frames is compared to the steel RC frame in terms of the damage level, the Maximum Inter-Storey Drift (MID) ratio, Maximum Residual Inter-Storey Drift (MRID), Maximum Roof Drift Ratio (MRDR), Residual Roof Drift Ratio (RRDR), and the earthquake intensity at collapse. Analysis results show improved seismic performance for the two retrofitted frames as compared to the original steel RC frame. This improvement was represented by lower level of damage at the same earthquake intensity; small reduction (10–15%) in the MID and MRDR values; significant reduction (50–70%) in the MRID and RRDR; and increased seismic capacity.

Reinforced concrete (RC) walls constitute the main lateral load resisting system for the majority of buildings. Their inelastic response allows dissipating the seismic energy. This behaviour ensures achieving the life safety performance level on the cost of inducing significant damage to the buildings. The effect of using Engineering Cementitious Composite (ECC) and Superelastic Shape Memory Alloy (SE-SMA) on the seismic damage and ductility of RC walls is examined in this paper. Seismic fragility curves for conventical steel RC walls and walls utilizing ECC and SE-SMA are developed for an assumed building. Results indicate that seismic damage in RC walls can be significantly reduced by utilizing ECC and/or SE-SMA.

Mitigation of seismic damage can be achieved through self-centering techniques. One of the potential techniques involves the use of Superelastic Shape Memory Alloy (SE-SMA) bars in Reinforced Concrete (RC) structures. This study explores the use of such bars in the plastic-hinge regions of RC walls. The seismic performance and vulnerability of SE-SMA RC walls of ten- and twenty-story buildings are analytically assessed using fragility curves. The maximum inter-story drift, residual drift, and fragility are evaluated using multi strip analysis. The results clearly demonstrate the superior seismic performance of SE-SMA RC walls as compared to steel RC walls.

Self-centering earthquake resistant systems have attracted the attention of researchers because of their promising potential in controlling seismic residual drifts, and, therefore, reducing the associated repair costs. The use of Ni-Ti superelastic shape memory alloy (SMA) constitutes a considerable portion of this research. Cu-Al-Mn superelastic SMA has been recently developed to eliminate the high cost of Ni-Ti SMA, as well as, to have better machining characteristics. This paper explores the use of Cu-Al-Mn SMA bars to relocate the plastic hinge of concrete beams through an experimental–numerical study. The cyclic performance of four beams was examined. The first was reinforced with steel bars and the remaining three were reinforced with combination of SMA and steel bars. The location of the SMA bars was different for each of the examined beams. The beams were loaded such that the moment diagram is zero at midspan and maximum at the ends to simulate the expected seismic moments. Results of the experimental–numerical investigation confirmed the recentering capability of SMA RC beams. Relocating the plastic hinge, by placing Cu-Al-Mn SMA bars away from the beam ends, improved the strength, rigidity, and energy dissipation.

Retrofitting Reinforced Concrete (RC) structures is required to upgrade their capacities and/or address deterioration happening overtime. Several retrofitting techniques and materials are available. More innovative and cost effective retrofitting techniques are continuously being developed. In this study, a new technique for retrofitting RC beams in flexure is introduced. The technique is based on using unbonded superleastic Shape Memory Alloy (SMA) bars. A sectional analysis approach is presented, validated, and used to conduct an extensive parametric study. Results of the parametric study are used to develop equations to predict changes in the beam behaviour because of the suggested retrofitting technique. .

A reinforced concrete (RC) dual system utilizes RC walls in conjunction with RC frames to resist seismic loads. High energy dissipation and low seismic deformations are its characteristics. This paper evaluates the effect of utilizing superelastic shape memory alloy (SE-SMA) bars on the engineering demand parameters of RC dual systems. Two steel RC dual systems are designed. The designs are then revised using SE-SMA bars. Two potential layouts for the locations of SE-SMA bars are examined, which resulted in four SE-SMA dual systems. Incremental dynamic analysis (IDA) is then conducted. SE-SMA RC dual systems are found to have superior seismic performance as compared to steel RC systems.

Trend of using smart structures, that can adjust their behaviour when exposed to severe unexpected loading, is increasing. One of the methods to achieve such structures relies on smart materials. For example, replacing conventional steel reinforcing bars in Reinforced Concrete (RC) structures with superelastic Shape Memory Alloy (SMA) bars significantly reduces the residual deformations caused by post-yielding behaviour. This paper provides in-depth understanding of the flexural behaviour of SMA RC beams. A sectional analysis method, that predicts the flexural behaviour of SMA RC beams during both loading and unloading stages, is adopted and validated using available experimental data. An extensive parametric study is then carried out to investigate the effect of different geometrical properties. Recommendations for the optimum amount and length of SMA bars are drawn based on results of this study.

Retrofitting Reinforced Concrete (RC) structures is required to upgrade their capacities and/or address deterioration happening overtime. Several retrofitting techniques and materials are available. More innovative and cost effective retrofitting techniques are continuously being developed. In this study, a new technique for retrofitting RC beams in flexure is introduced. The technique is based on using unbonded superleastic Shape Memory Alloy (SMA) bars. The technique is first assessed using the Finite Element (FE) method. A simplified sectional analysis approach is then presented, validated, and used to conduct an extensive parametric study. Results of the parametric study are used to develop equations to predict changes in the beam behaviour because of the suggested retrofitting technique.

One of the problems for existing reinforced concrete (RC) structures designed per older standards (pre 1970s) is the inadequate anchorage for the beam reinforcement in the joint area. For newly built structures, Beam-column joints (BCJs) may need to be retrofitted to accommodate changes in the structure use or an increase in the applied loads. Shape Memory Alloys (SMAs) have unique properties that motivated researchers to use them as reinforcing bars in RC structures. They can undergo large deformations and return to their undeformed shape upon unloading. This unique property can be utilized in RC structures subjected to seismic loads to limit residual deformations. In this study, the applicability of using external unbonded SMA bars to retrofit RC BCJs is investigated. A finite element (FE) model is first
developed and validated. A simplified model is then proposed and used to conduct a parametric study to investigate the behaviour of SMA retrofitted RC BCJs.

Pre-1970s designed and built reinforced concrete frame structures are considered unsafe when subjected to seismic loads. Insufficient anchorage of the beam reinforcement in the joint area of the beam column joints of these structures is considered a main deficiency. Newly built frame structures are seismically designed for safety, where high inelastic deformations are allowed to occur under moderate to strong earthquakes. Minimizing these inelastic deformations make the structure repairable. One way to minimize these residual deformations is by using smart materials such as superelastic Shape Memory Alloys (SMAs). In this paper, the seismic performance of RC frames retrofitted using external superleastic SMA bars is investigated and compared to the behaviour of a regular steel RC frame structure. Nonlinear time history analysis is performed for a six storey RC frame structure located in high seismic region. After performing the analysis, two retrofitted frames are assumed. Analysis is performed again for the two frames at the load intensities causing failure of the steel RC frame. The performance of the retrofitted frames is compared to the steel RC frame in terms of the Maximum Inter-storey Drift (MID) ratio, Maximum Residual Inter-storey Drift (MRID), Maximum Roof Drift Ratio (MRDR), and Residual Roof Drift Ratio (RRDR).

Reinforced concrete (RC) framed buildings dissipate the seismic energy through yielding of the reinforcing bars. This yielding jeopardizes the serviceability of these buildings as it results in residual lateral deformations. Superelastic shape memory alloys (SMAs) can recover inelastic strains by stress removal. This paper extends previous research by the authors that optimized the use of SMA bars in RC frames considering the horizontal seismic excitation by addressing the effect of the vertical seismic excitation. A steel RC six-storey building designed according to current seismic standards is considered as case study. Five different earthquake records with strong vertical components are selected for the nonlinear dynamic analysis. The results were used to evaluate the effect of the vertical excitation on the optimum locations of SMA bars.

The uniqueness of superelastic Shape Memory Alloy (SMA) bars lies in their ability to undergo large deformations and return to their undeformed shape through stress removal. In conventional seismic design of civil structures, inelastic deformations are allowed to dissipate the seismic energy. Such design philosophy results in permanent residual deformations, which complicate the post-earthquake retrofitting efforts. This keynote lecture summarizes Dr. Youssef’s research that utilizes superelastic SMA bars to reduce or eliminate seismic residual deformations. The lecture will summarize the characteristics of superelastic SMA bars and highlight challenges facing their implementation in future construction projects. It will then cover research addressing their use in Reinforced Concrete (RC) moment frames. Experimental tests of RC beam-column joints provided the initial proof that superelastic SMA bars can upgrade our RC framed structures to sustainable ones that can be easily repaired following a strong seismic excitation. Incremental dynamic analysis identified the optimum locations of superelastic SMA bars in a typical RC frame. Other applications including the use of superelastic SMA bars in brace members, RC walls, steel frames, and modular steel buildings will also be presented.

Steel structures dissipate the seismic energy through steel yielding, which results in residual deformations. Although conventional earthquake-resisting structural systems provide adequate seismic safety, they experience significant structural damage when exposed to strong ground shaking. Seismic residual drifts complicate the repair of damaged structures or render the structure as irreparable. Therefore, systems that can minimize the seismic residual deformations are needed. Superelastic shape memory alloys (SMAs) have the ability to undergo large deformations and recover all plastic deformations upon unloading. Their utilization in steel structures can significantly reduce seismic residual deformations, which will facilitate post-seismic retrofitting. Although the literature provides few research data on using SMA in steel beam-column connections, previous research did not address their optimum use. This paper identifies the required locations of SMA connections in a typical steel moment resisting frame to enhance its seismic performance in terms of maximum inter-storey drift, residual deformations, and damage scheme.

The need for sustainable structures, that provide adequate ductility without experiencing major damage, has led researchers to develop methods to achieve self-centering structures. One of these methods involves the use of superelastic Shape Memory Alloy (SMA) bars. This study assesses the seismic performance of a three-story SMA Reinforced Concrete (RC) shear wall considering different potential locations for the SMA bars. The maximum inter-story drift, residual drift, and damage scheme are evaluated using Incremental Dynamic Analysis (IDA). The use of SMA bars at the plastic hinge of the first floor was found to significantly reduce the residual drifts and associated damage.

Concrete walls are commonly used to resist lateral loads. Their relatively high stiffness limits the inter-story drifts and minimizes damage to other structural and nonstructural elements. However, significant structural damage to the walls is expected during seismic events. This study investigates numerically the effectiveness of using Superelastic (SE) Shape Memory Alloy (SMA) bars to improve the seismic performance of moderate and squat concrete walls. The used analytical model was validated using experimental results by others. It was then utilized to investigate the cyclic load-displacement response of one-intermediate and two-squat walls while incorporating SMA bars. Results of this study led to identifying the location of SMA bars that result in best seismic performance

Shape Memory Alloy (SMA) braces can be used to reduce seismic residual deformations observed in steel braced Reinforced Concrete (RC) frames. To further enhance the seismic performance of these frames, the use of SMA bars to reinforce their beams is investigated in this paper. Three-story and nine-story SMA-braced RC frames are designed utilizing regular steel reinforcing bars. Their seismic performance is examined using twenty seismic ground motions. The frames are then re-designed using SMA reinforcing bars. Different design alternatives representing different locations for the SMA reinforcing bars are considered. The optimum locations for the SMA bars are identified after analysing the design alternatives. The seismic performance of these frames has indicated better deformability when SMA bars are used in the beams.

Reinforced concrete (RC) framed buildings dissipate the seismic energy through yielding of the reinforcing bars. This yielding jeopardizes the serviceability of these buildings as it results in residual lateral deformations. Superelastic Shape Memory Alloys (SMAs) can recover inelastic strains by stress removal. Since SMA is a costly material, this paper defines the required locations of SMA bars in a typical RC frame to optimize its seismic performance in terms of damage scheme and seismic residual deformations. The intensities of five earthquakes causing failure to a typical RC six-storey building are defined and used to evaluate seven SMA design alternatives.

Large-scale earthquakes pose serious threats to infrastructure causing substantial damage and large residual deformations. Superelastic (SE) Shape-Memory-Alloys (SMAs) are unique alloys with the ability to undergo large deformations, but can recover its original shape upon stress removal. The purpose of this research is to exploit this characteristic of SMAs such that concrete Beam-Column Joints (BCJs) reinforced with SMA bars at the plastic hinge region experience reduced residual deformation at the end of earthquakes. Another objective is to evaluate the seismic performance of SMA Reinforced Concrete BCJs repaired with flowable Structural-Repair-Concrete (SRC). A -scale BCJ reinforced with SMA rebars in the plastic-hinge zone was tested under reversed cyclic loading, and subsequently repaired and retested. The joint was selected from an RC building located in the seismic region of western Canada. It was designed and detailed according to the NBCC 2005 and CSA A23.3-04 recommendations. The behaviour under reversed cyclic loading of the original and repaired joints, their load-storey drift, and energy dissipation ability were compared. The results demonstrate that SMA-RC BCJs are able to recover nearly all of their post-yield deformation, requiring a minimum amount of repair, even after a large earthquake, proving to be smart structural elements. It was also shown that the use of SRC to repair damaged BCJs can restore its full capacity.

Using superelastic shape memory alloys (SMAs) as reinforcing bars in concrete structures proved to have a great potential in seismic areas because of its recentering capability. However, using them in an entire structure is generally not economically feasible due to their high cost. Therefore, it is more practical to limit their use to the plastic hinge zones, while regular steel can be used in the other regions of the structure. Connections between SMA and steel are critical, and need to be strong enough to transfer the full force from SMA bars to steel bars. Various mechanical couplers are available in the market to splice bars in reinforced concrete (RC) structures, each of which has several advantages and disadvantages. The efficiency of these couplers for connecting steel bars is tested and reported in this paper. Since these couplers are intended for connecting steel bars only, another experimental investigation has been performed to determine the suitability of these couplers for connecting SMA with steel bars. Commercially available screw-lock couplers are found to be unsuitable for connecting SMA to steel bars. An existing coupler has been modified for SMA–steel splicing to allow SMA bars to achieve their full superelastic strain. Additional tests have also been performed for connecting FRP bars to SMA bars. A new generation mechanical-adhesive type coupler has been developed for splicing FRP to SMA bars.

The use of Fibre-Reinforced Polymer (FRP) as reinforcement in concrete structures has received much attention owing to its higher resistance to corrosion compared to that of regular steel reinforcement. Since FRP is a brittle material, its use in seismic resisting structural elements has been a concern. FRP RC structures can be made ductile by utilizing a ductile material such as steel at the plastic hinge regions. However, the use of steel negates the corrosion resistance purpose of FRP. On the other hand, Nickel–Titanium (Ni–Ti) shape memory alloy (SMA) is highly resistant to corrosion. It also brings about an added advantage in seismic regions since it has the unique ability to undergo large deformation, but can regain its undeformed shape through stress removal. In this study, a SMA–FRP hybrid RC beam–column joint has been proposed to address not only corrosion resistance, but also seismic related problems. This joint is reinforced with a super-elastic Ni–Ti SMA bar at the plastic hinge regions of the beam and FRP in the other regions of the beam and column. To validate the proposed joint, an experimental investigation has been carried out to develop such a joint and test it under reversed cyclic loading. The results are compared in terms of load–storey drift, moment–rotation and energy dissipation capacity to those of a similar RC beam–column joint specimen reinforced with conventional steel. The SMA–FRP beam–column joint proved to have adequate energy dissipation under earthquake type loading.

The need for a new model capable of accurately predicting the deflection of shape memory alloy (SMA) reinforced concrete (RC) beams is clear from the results obtained in the companion paper. In the present paper, artificial neural networks (ANNs) are utilized to develop such a model. The objective is to create a design tool for computing a reduction factor β to be used in the calculation of the effective moment of inertia for SMA RC beams. First, a database was developed using the results obtained from the parametric study reported in the companion paper. The main factors affecting the moment of inertia have been considered. The network architecture that results in the optimum performance was selected and trained. After demonstrating the network’s ability to predict output data for unfamiliar input data, the network was used to develop a design chart that provides the reduction factor β as a function of the reinforcement ratio and the reinforcement modulus of elasticity. A design example is discussed to illustrate the advantages of using the developed design chart over existing models.

This paper investigates the load–deflection behaviour of shape memory alloy (SMA) reinforced concrete (RC) beams through a parametric study. The effects of the cross-section height, cross-section width, reinforcement ratio, reinforcement modulus of elasticity, and concrete compressive strength were considered. The sectional analysis methodology was adopted to predict the moment–curvature relationship for the considered sections. Deflection was then estimated using the moment–area method. The applicability of this method for SMA RC beams was demonstrated through comparisons with available experimental results. Based on the results of the parametric study, an assessment of the available models for deflection analysis of SMA RC beams was conducted. The accuracy and reliability of the different models were evaluated, and suitable models were recommended. A companion paper provides the development of an artificial intelligence based model that can predict the deflection of SMA RC beams more accurately than existing models.

Concentric bracing systems have proven to be effective in limiting the lateral drifts of Reinforced Concrete (RC) frames. One of the known deficiencies for these systems is the expected residual deformations following a seismic event. This paper focuses on evaluating the effect of using Buckling Restrained Braces (BRBs) and Shape Memory Alloy Braces (SMABs) on the seismic performance of a three-storey RC building. Two RC frames are designed utilizing both BRBs and SMABs and analyzed using pushover and dynamic analyses. The SMAB system is found to significantly reduce seismic residual deformations. However, this advantage is lost at peak ground accelerations close to the peak ground acceleration causing failure of the frame.

Superelastic Shape Memory Alloys (SMAs) are unique materials which can regain their original length upon unloading. Utilizing superelastic SMA bars in Reinforced Concrete (RC) frames results in dissipating the earthquake energy while minimizing the seismic residual deformations. In this study, the critical sections of a six-storey steel RC building are defined using five different earthquake records. The building was then redesigned using SMA bars. Seven alternative designs were explored representing using the SMA bars at the plastic hinge zones of the critical beam/column sections and/or at the beam sections adjacent to the critical columns. Each design alternative was subjected to dynamic analysis using the chosen five records scaled to the intensity causing severe damage to the steel RC frame. It was concluded that using SMA bars at the critical beam sections and at the beam sections adjacent to the critical columns results in minimal local damage and residual drifts.

Different types of mechanical couplers are used to splice rebars in reinforced concrete (RC) structures. The efficiency of these couplers for connecting steel rebars has been tested and reported in this paper. Recently, superelastic shape memory alloy (SMA) proves to have a great potential to be used as reinforcing bars in concrete structures in seismic areas. However, using SMA bars in entire structures is not economically feasible due to its high cost. Therefore, it is more rational to limit its use in the plastic hinge regions, whereas regular steel can be used in the other regions of the structure. The connections between SMA and steel are critical, and must be able to transfer the full force from SMA bar to steel bar. Since existing couplers have been developed for connecting steel bars, an experimental investigation was performed to determine their suitability for connecting SMA to steel bar. Commercially available screw-lock couplers were found to be unsuitable. Special treatment needs to be done to achieve the full superelastic strain of SMA while connected with steel bar. None of the available couplers provided adequate performance for SMA spliced bars. Hence, an existing coupler was modified for SMA-steel splicing.

High corrosion resistance has made Fibre-Reinforced Polymer (FRP) bars increasingly accepted as reinforcement in concrete structures. However, the lack of ductility is a major concern for the use of FRP reinforcement in seismic regions. However, FRP reinforced concrete (RC) structures can be made ductile by utilizing a ductile material such as steel at the plastic hinge regions. However, the use of steel negates the corrosion resistance purpose of FRP. Nickel-Titanium (Ni-Ti) shape memory alloy (SMA) is highly resistant to corrosion and has added advantage in seismic regions since it can undergo large deformation, yet regain its undeformed shape through stress removal. In this study, an FRP RC beam-column joint with SMA bar at the plastic hinge region of the beam is proposed to address both corrosion resistance and seismic related problems. This joint is reinforced with superelastic Ni-Ti SMA bar at the plastic hinge regions of the beam and FRP in the other regions of the beam and column. The performance of the proposed joint is studied under reversed cyclic loading. The results were compared, in terms of loadstorey drift, and energy dissipation capacity, to those of the original specimen. Both the original and repaired joints proved to dissipate adequate energy under earthquake type loading. The proposed BCJ is not only corrosion resistant, but can also provide adequate energy dissipation during large earthquakes, therefore mitigating major problems related to infrastructure management.

Superelastic Shape Memory Alloys (SMAs) are gaining acceptance for use as reinforcing bars in concrete structures. The seismic behaviour of concrete frames reinforced with SMAs is being assessed in this study. Two eight-storey concrete frames, one of which is reinforced with regular steel and the other with SMAs at the plastic hinge regions of beams and regular steel elsewhere, are designed and analyzed using 10 different ground motion records. Both frames are located in the highly seismic region of Western Canada and are designed and detailed according to current seismic design standards. The validation of a finite element (FE) program that was conducted previously at the element level is extended to the structure level in this paper using the results of a shake table test of a three-storey moment resisting steel RC frame. The ten accelerograms that are chosen for analyzing the designed RC frames are scaled based on the spectral ordinate at the fundamental periods of the frames. The behaviour of both frames under scaled seismic excitations is compared in terms of maximum inter-storey drift, top-storey drift, inter-storey residual drift, and residual top-storey drift. The results show that SMA-RC frames are able to recover most of its post-yield deformation, even after a strong earthquake.

The unique properties of superelastic shape memory alloys (SMAs) have motivated researchers to explore their use as reinforcing bars. The capacity of a steel reinforced concrete (RC) section is calculated by assuming a maximum concrete strain εc-max and utilizing stress block parameters, α1 and β1, to simplify the non-linear stress–strain curve of concrete. Recommended values for εc-max, α1, and β1 are given in different design standards. However, these values are expected to be different for SMA RC sections. In this paper, the suitability of using sectional analysis to evaluate the monotonic moment–curvature relationship for SMA RC sections is investigated. A parametric study is then conducted to identify the characteristics of this relationship for steel and SMA RC sections. Specific mechanical properties are assumed for both steel and SMA. Results were used to evaluate εc-max, α1, and β1 values given in the Canadian standards and to propose equations to estimate their recommended values for steel and SMA RC sections.

Superelastic shape memory alloys (SMAs) are unique materials that have the ability to undergo large deformations, but can return to their undeformed shape by the removal of stress. If such materials can be used as reinforcement in plastic hinge regions of beam–column elements, they will not only experience large inelastic deformations during strong earthquakes, but can potentially recover their original shape. This behaviour will allow mitigating the problem of permanent deformation. Hence, this study aims at establishing guidelines for predicting the seismic behaviour of concrete beam–column elements reinforced with superelastic SMAs. The paper identifies the disparities in moment–curvature relationship between SMA and steel reinforced sections. Then it examines the applicability of existing methods developed for steel reinforced concrete (RC) members to predict the length of the plastic hinge, crack width, crack spacing, and bond-slip relationship for superelastic SMA RC elements. Existing superelastic SMA models are discussed and the application of one of the models in a finite element (FE) program is presented. This FE program is used to simulate the behaviour of an SMA RC column and a beam–column joint. The predicted load–displacement, moment–rotation relationships and energy dissipation capacities have been found to be in good agreement with experimental results.

Superelastic Shape Memory Alloys (SE SMAs) are unique alloys that have the ability to undergo large deformations and return to their undeformed shape by removal of stresses. This study aims at assessing the seismic behavior of beam-column joints reinforced with SE SMAs. Two large-scale beam-column joints were tested under reversed cyclic loading. While the first joint was reinforced with regular steel rebars, SE SMA rebars were used in the second one. Both joints were selected from a Reinforced Concrete (RC) building located in the high seismic region of western Canada and designed and detailed according to current Canadian standards. The behavior of the two specimens under reversed cyclic loading, including their drifts, rotations, and ability to dissipate energy, were compared. The results showed that the SMA-reinforced beam-column joint specimen was able to recover most of its post-yield deformation. Thus, it would require a minimum amount of repair even after a strong earthquake.

Shape Memory Alloys (SMAs) are unique materials with a paramount potential for various applications in bridges. The novelty of this material lies in its ability to undergo large deformations and return to its undeformed shape through stress removal (superelasticity) or heating (shape memory effect). In particular, Ni-Ti alloys have distinct thermomechanical properties including superelasticity, shape memory effect, and hysteretic damping. SMA along with sensing devices can be effectively used to construct smart Reinforced Concrete (RC) bridges that can detect and repair damage, and adapt to changes in the loading conditions. SMA can also be used to retrofit existing deficient bridges. This includes the use of external post-tensioning, dampers, isolators and/or restrainers. This paper critically examines the fundamental characteristics of SMA and available sensing devices emphasizing the factors that control their properties. Existing SMA models are discussed and the application of one of the models to analyze a bridge pier is presented. SMA applications in the construction of smart bridge structures are discussed. Future trends and methods to achieve smart bridges are also proposed.

The use of Fibre Reinforced Polymer (FRP) as reinforcement in concrete structures has received much attention owing to its higher resistance to corrosion compared to that of regular steel reinforcement, and has been a very active research area for the last two decades. Since FRP is a brittle material, ductility is considered as a major concern for FRP-reinforced concrete (RC) structures. Ductility of FRP RC structures can be achieved in conjunction with a ductile material such as steel, or shape memory alloy (SMA) which can be placed at the plastic hinge regions of a structure, while FRP bars can be used in the other regions of the structure. However, the use of steel involves the risk of corrosion. Nickel-Titanium (Ni-Ti) SMA is highly resistant to corrosion. If superelastic Ni-Ti can be used as reinforcement, it brings about added advantage in seismic regions since it has the ability to undergo large deformation, but can regain its undeformed shape through stress removal. In this research, beam-column joints reinforced with superelastic Ni-Ti SMA rebar at the plastic hinge regions of the beam and FRP in other regions of the beam and column have been tested under reversed cyclic loading. The results are compared in terms of load-storey drift and energy dissipation capacity to those of a similar RC beam-column joint specimen reinforced with conventional steel. eventually help in eliminating the majority of infrastructure management problems.

Recently two experimental investigations were carried out on beam-column elements under seismic loading, one in the University of Western Ontario and the other in the University of Nevada, Reno, where superelastic Shape Memory Alloy (SMA) rebars were used as reinforcement at their plastic hinge regions. Such SMA reinforced beam-column elements experienced reduced residual deformation at the end of seismic loading. This study aims in developing finite element (FE) models in order to simulate the seismic behaviour of SMAreinforced concrete (RC) beam-column elements. The predicted behaviour of the two specimens from FE analysis, their load-storey drift relationship, and energy dissipation ability are compared with the experimental results. The results showed that the model could predict the behaviour of both SMA-RC beam-column elements with reasonable accuracy.

The objective of this study is to evaluate the seismic performance of a repaired concrete Beam-Column Joint (BCJ) specimen reinforced with superelastic (SE) Shape Memory Alloy (SMA) rebar. A large-scale BCJ reinforced with SMA rebars in the plastic-hinge zone was tested under reversed cyclic loading. Then the joint was repaired and retested. The joint was selected from an eightstorey RC building located in the high seismic region of western Canada and designed and detailed according to the NBCC 2005 and CSA A23.3-04 recommendations. The behaviour of the original and repaired joints under reversed cyclic loading, their load-storey drift, and energy dissipation ability were compared. The results demonstrate that SMA-RC BCJs are able to recover nearly all of their post-yield deformation requiring minimum amount of repairing even after a large earthquake.

Shape Memory Alloys (SMAs) are novel materials that have many applications in different fields. The unique properties of SMA such as Superelasticity (SE) and Shape Memory Effect (SME) have made it distinctive to other metals and alloys. These unique properties have motivated researchers to utilize it in civil engineering applications. One of these applications is using SMA as reinforcing bars in Reinforced Concrete (RC) members. The lack of understanding of the behaviour of SMA RC members has limited its use as reinforcing bars. This behaviour can be understood by developing the moment-curvature relationship for SMA RC sections. Due to the unique properties of SMA and the difference in the stress-strain relationship between steel and SMA, the stress-block parameters provided by the Canadian standards to design steel RC sections might not be valid for designing SMA RC sections. In this paper, moment-curvature analyses were conducted for a range of SMA RC concrete sections. The results of these analyses allowed evaluating the capacities of SMA RC sections and the corresponding maximum concrete strain. Results were used to evaluate the validity of using the stress block parameters provided by the Canadian standards in designing SMA RC sections.

Shape memory alloys (SMAs) are special materials with a substantial potential for various civil engineering applications. The novelty of such materials lies in their ability to undergo large deformations and return to their undeformed shape through stress removal (superelasticity) or heating (shape-memory effect). In particular, SMAs have distinct thermomechanical properties, including superelasticity, shape-memory effect, and hysteretic damping. These properties could be effectively utilized to substantially enhance the safety of various structures. Although the high cost of SMAs is still limiting their use, research investigating their production and processing is expected to make it more cost-competitive. Thus, it is expected that SMAs will emerge as an essential material in the construction industry. This paper examines the fundamental characteristics of SMAs, the constitutive material models of SMAs, and the factors influencing the engineering properties of SMAs. Some of the potential applications of SMAs are discussed, including the reinforcement and repair of structural elements, prestress applications, and the development of kernel components for seismic devices such as dampers and isolators. The paper synthesizes existing information on the properties of SMAs, presents it in concise and useful tables, and explains different alternatives for the application of SMAs, which should motivate researchers and practicing engineers to extend the use of SMAs in novel and emerging applications.Key words: shape memory alloy, superelasticity, shape-memory effect, construction, retrofitting.

Superelastic Shape Memory Alloys (SMAs) are unique alloys that have the ability to undergo large deformations, but can return to their undeformed shape by removal of stresses. This study investigates the seismic performance of joints reinforced with superelastic SMAs compared to regular steel. A finite element program has been validated and then used to analyze two concrete beam-column joints under reversed cyclic loading. Both joints were chosen from an eight storey-RC building located in the high seismic region of western part of Canada. The building was designed and detailed according to the NBCC 2005 and CSA A23.3-04 recommendations. The first specimen was reinforced using steel reinforcing bars. In the second specimen, SMAs were used as reinforcement at the plastic hinge region. The behaviour of the two specimens under reversed cyclic loading, their load-displacement relationship, and energy dissipation ability were compared. The SMA-reinforced specimen ductility and energy dissipation capacity were comparable to the steel reinforced specimen. The results showed that SMAreinforced specimen was able to recover most of its post-yield deformation requiring minimum amount of repair even after a strong earthquake.

Shape Memory Alloys (SMAs) are unique materials with high potential for various applications in bridges. The novelty of this material lies in its ability to undergo large deformations, and return to its undeformed shape through stress removal (superelasticity) or heating (shape memory effect). In particular, Ni-Ti alloys have distinct thermomechanical properties including: superelasticity, shape memory effect, and hysteretic damping. SMA can be effectively used in developing a smart Reinforced Concrete (RC) bridge which will be able to sense and detect its own damage, repair its condition, and adapt to changes in loading conditions. Existing deficient bridges can also be retrofitted by external post-tensioning using SMA. In addition, seismic retrofitting can be effectively done using various SMA dampers, isolators and/or restrainers. This paper examines the fundamental characteristics of SMA emphasizing the factors controlling its properties. The paper also presents the concept of developing a smart RC bridge with SMA applications in the construction of bridge structures along with its future trends and applications.

Shape Memory Alloys (SMAs) are unique materials with the ability to undergo large deformations, and return to their undeformed shape through stress removal (superelasticity) or heating (shape memory effect). This makes them potential candidates for use in seismic resisting elements in the form of reinforcing bars, bracings, and/or connectors. Because of their high damping, they have been used as the kernel components of various damping devices, isolators and actuators for passive, semi-active and active seismic control of structures. Moreover SMAs have been efficiently used for rapid and convenient repair and strengthening of seismically damaged or deficient structures. This paper presents state-of-theart of numerous seismic applications of SMAs and their devices in various structures. The paper also reviews the fundamental characteristics of SMAs emphasizing on the factors influencing their properties.

Shape Memory Alloys (SMAs) are special materials with great potential in various civil engineering applications. The novelty of this material lies in its ability to undergo large deformations, and return to its undeformed shape through stress removal (superelasticity) or heating (shape memory effect). Among prospective SMA candidates, Ni-Ti alloys have distinct thermomechanical properties including: superelasticity, shape memory effect, and hysteretic damping. This led to numerous applications including: self-sensing, repairing of structural elements, prestressing, external post-tensioning, and developing kernel components for seismic devices (actuators, dampers, and isolators). Although the high cost of SMA is still limiting its use, researches investigating its production and processing are expected to reduce significantly its price. It is only a matter of time and SMA will emerge as an essential material in the construction industry. This paper reviews the fundamental characteristics of SMA emphasizing the factors influencing their properties and constitutive material models. The paper also presents a review of the state-of-the-art of SMA applications in the construction of civil engineering structures along with its future trends and applications.