Performance of shape memory alloy reinforced concrete frames under extreme loads

Reinforced concrete (RC) frame structures are commonly used in various parts of the world for resisting lateral loads. Over the last few decades, the influence of extreme loads on structures has received much attention by researchers and practicing engineers. In RC structures steel is mainly used as reinforcing material where its major setback is associated with a high residual deformation after yielding during an extreme load event, which may often result in structural collapse or substantial damages to the structure. Superelastic shape memory alloy (SMA) is a special material, which has the ability to undergo large deformation and recover its shape upon unloading. In the present study, a numerical investigation has been carried out to determine the potential application of SMA rebar in improving the performances of reinforced concrete (RC) frames under extreme loads. Nine RC ductile moment-resisting frames of different stories (3, 6 and 8) designed as per CSA A23.3 located in western Canada are taken into consideration. For each storey type, three different reinforcement detailings have been considered, namely: i) steel reinforcement only (Steel RC); ii) SMA rebar used in the plastic hinge region of the beams and steel rebar in other regions (Steel-SMA RC); and iii) the beams fully reinforced with SMA rebar (SMA RC). For all 3 cases, the columns were reinforced with steel rebars. Nonlinear static pushover analyses, nonlinear incremental dynamic and linear dynamic time history analyses were performed on these buildings to determine the overstrength factor (Ro), ductility reduction factor (Rd) and the response modification factor (R) of the considered buildings. In addition, the supply and demand of the ductility reduction factor were also compared with different frame types. The results indicated that the code proposed response modification factors can be used for the SMA and Steel-SMA RC frames. Seismic vulnerability of the considered frames are also evaluated in terms of peak global roof drift, maximum inter-story drift, maximum residual roof drift and maximum residual inter-storey drift, which are considered as critical response parameters. In addition, the progressive collapse performances of the considered frames have been evaluated as per the General Service Administration (GSA, 2003) guideline by performing linear and nonlinear static and dynamic, analyses. The results showed that the performance of the Steel RC frame is better compared to that of the SMA RC frame under progressive collapse.Applied Science, Faculty ofEngineering, School of (Okanagan)Graduat