STR-852: PERFORMANCE ASSESSMENT OF THREE-STORY SHAPE MEMORY ALLOY REINFORCED CONCRETE WALLS

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

Seismic fragility assessment of superelastic shape memory alloy reinforced concrete shear walls

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

Seismic Performance of Superelastic Shape Memory Alloy Reinforced Concrete Shear Wall Systems

A major sustainability issue for reinforced concrete (RC) structures is the residual deformations caused by the yielding of the steel bars during extreme seismic events. Numerous efforts have been made to develop self-centering structures, which minimize these deformations and the associated seismic damage. Superelastic shape memory alloys (SE-SMA) can be utilized in concrete elements to achieve such behaviour. This thesis focuses on the use of SE-SMA bars in RC walls. First, the thesis starts by conducting a fragility analysis to assess the seismic performance and vulnerability of ten and twenty-story SE-SMA RC walls. SE-SMA bars are used within the plastic hinge length of the walls and are assumed to replace all longitudinal steel bars or those reinforcing the boundary elements. The considered walls were found to possess an adequate margin of safety against collapse as compared to steel RC walls. Due to the unique properties of SE-SMA material, the ductility and overstrength factors for SE-SMA RC walls are then evaluated. Nine-hundred and seventy-two walls were analyzed to investigate the effects of different design parameters on the ductility and overstrength factors. Suggested values for the design factors were then evaluated by conducting nonlinear time history analyses for three, six, and nine-story buildings. The seismic performance of SE-SMA RC dual systems is evaluated. Incremental dynamic analysis is carried out under considering different seismic load events. Results allowed choosing a suitable SE-SMA layout for dual systems to achieve good seismic performance. The seismic performance of RC core walls is significantly different from rectangular RC walls because of their ability to resist bidirectional and torsional loading. The seismic performance of reinforced concrete core walls under unidirectional and bidirectional seismic excitations, while accounting for variations in the torsional eccentricity, was examined. SE-SMA bars reduced not only the mean lateral displacements but also the floor rotations. Finally, and to mitigate the seismic residual deformations and corrosion problems associated with steel RC walls, the seismic performance of walls reinforced with SE-SMA bars or hybrid (SMA-FRP) bars over the plastic hinge length and fiber-reinforced polymers (FRP) elsewhere is examined. The SMA-FRP bars resulted in a significant improvement in the wall capacity as compared to SE-SMA bars. Also, they resulted in lower seismic damage

Seismic performance of concrete core walls reinforced with shape memory alloy bars

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

Seismic Performance of Hybrid Corrosion-Free Self-Centering Concrete Shear Walls

Reinforced concrete (RC) walls are extensively used in high-rise buildings to resist lateral loads, while ensuring an adequate level of ductility. Durability problems, including corrosion of conventional steel reinforcements, necessitate exploring alternative types of reinforcement. The use of glass fiber reinforced polymer (FRP) bars is a potential solution. However, these bars cannot be used in seismic applications because of their brittleness and inability to dissipate seismic energy. Superelastic shape memory alloy (SMA) is a corrosion-free material with high ductility and unique self-centering ability. Its high cost is a major barrier to use in construction projects. The clear advantage of utilizing both SMA and FRP to achieve durable self-centering structures has motivated the development of a composite SMA-FRP bar. This paper investigates the hybrid use of FRP bars and either SMA bars or composite SMA-FRP in concrete shear walls. An extensive parametric study was conducted to study the effect of different design parameters on the lateral performance of hybrid RC walls. The seismic behavior of the hybrid walls was then examined. The hybrid walls not only solved the durability problem but also significantly improved the seismic performance

Seismic Performance of Hybrid Corrosion-Free Self-Centering Concrete Shear Walls

Reinforced concrete (RC) walls are extensively used in high-rise buildings to resist lateral loads, while ensuring an adequate level of ductility. Durability problems, including corrosion of conventional steel reinforcements, necessitate exploring alternative types of reinforcement. The use of glass fiber reinforced polymer (FRP) bars is a potential solution. However, these bars cannot be used in seismic applications because of their brittleness and inability to dissipate seismic energy. Superelastic shape memory alloy (SMA) is a corrosion-free material with high ductility and unique self-centering ability. Its high cost is a major barrier to use in construction projects. The clear advantage of utilizing both SMA and FRP to achieve durable self-centering structures has motivated the development of a composite SMA-FRP bar. This paper investigates the hybrid use of FRP bars and either SMA bars or composite SMA-FRP in concrete shear walls. An extensive parametric study was conducted to study the effect of different design parameters on the lateral performance of hybrid RC walls. The seismic behavior of the hybrid walls was then examined. The hybrid walls not only solved the durability problem but also significantly improved the seismic performance

Ductility and overstrength of shape-memory-alloy reinforced-concrete shear walls

The unique properties of superelastic shape-memory-alloy (SMA) bars have motivated researchers to investigate their use as reinforcing bars for concrete elements. They were found to decrease seismic residual deformations, while increasing seismic inelastic deformations. This characteristic deformation behaviour requires an assessment of the seismic design parameters of SMA reinforced concrete walls. This paper addresses this requirement by evaluating their ductility and overstrength factors. A total of 972 walls were analyzed under a quasi-static lateral load. Suitable values for the overstrength and ductility factors were estimated for two proposed locations of SMA bars. FEMA P695 was then utilized to evaluate the seismic safety margin for case study buildings, which were designed based on the estimated seismic design parameters