Experimental evaluation of ductile fiber reinforced cement-based composite beams incorporating shape memory alloy bars

The objective of the study is to explore the use of two promising materials, i.e., ductile fiber reinforced cement-based composites (DFRCCs) and shape memory alloys (SMA), in structural beams for enhanced seismic performance. DFRCCs are distinguished from regular concrete materials by their tensile strain hardening behavior accompanying by multiple hairline cracks. The unique tensile behavior in the material scale transforms into the enhanced ductility, shear and moment resistance, and damage tolerance in the structural scale. SMAs, a type of smart materials, are featured by their shape memory effect and superelasticity. The properties allow deformed SMAs with a strain as large as 8% to recover their original shape. The cyclic behavior of DFRCC beams reinforced by SMA bars is examined in the study. Four different beam specimens with experimental parameters, including DFRCCs, SMA bars, and bond strength between rebar and DFRCCs, are designed and tested. The results show that the use of DFRCCs to replace conventional concrete materials is able to enhance the energy dissipation capacity and failure pattern of the beam specimen. The reduced bond strength between rebar and the surrounding cement composites in the critical region of the beam is found to improve the ductility of the beam under displacement reversals. The beam specimen that employs SMA bars to replace regular steel bars in the longitudinal reinforcement exhibits appealing self-centering properties with very minor residual deformation after undergoing a drift response of 5%.