Seismic performance and shear strength of coupling beams using engineered cementitious composites with different reinforcement layouts

Abstract

The coupling beam is the key component in high-rise coupled-wall and core-tube structures. To further improve the seismic performance and damage tolerance of traditional reinforced concrete coupling beams, engineered cementitious composites (ECC) becomes a prospective choice, due to the superior characteristics including tension strain-hardening and multi-cracking properties. However, there have been only limited researches on ECC coupling beams, causing the lack of comprehensive understanding of the seismic behaviour and practical design formula. In this study, eight large-scale ECC coupling beam specimens with different aspect ratios, transverse and diagonal reinforcement ratios are fabricated and cyclically tested. The seismic performance of coupling beams is thoroughly investigated in terms of the damage and failure modes, energy dissipation, stiffness deterioration, strength degradation and shear distortion. The contribution of ECC, transverse and diagonal reinforcement to the shear strength is evaluated and compared. Besides, the whole-process hysteretic curves of the axial force are reported for the first time. Finally, a shear strength equation is proposed based on the analysis of nineteen specimens collected from the literature and this study. The test results demonstrate that ECC coupling beams with a hybrid reinforcement layout exhibit superior seismic performance, which is a reasonable choice to balance both the seismic and construction performance. It is strongly recommended that axial force should be considered in the strength prediction of coupling beams, with a 10% axial force ratio suggested for design. The proposed method is verified and can give precise prediction for the bearing capacity of ECC coupling beams.