Seismic behavior of steel reinforced ECC or ECC/concrete composite short columns

Abstract

Engineered cementitious composites (ECC) is an advanced composite material with strain hardening and multiple cracking behaviors. For a reinforced concrete short column, substitution of conventional concrete with ECC can significantly improve the deformation and energy dissipation ability. In this paper, it is proposed that concrete in the bottom region (plastic hinge region) of short columns is substituted with ECC to form ECC/RC composite short columns to improve the seismic performance and economic efficiency. Firstly, two ECC/RC composite short columns, one ECC short column and one RC short column were tested under reversed cyclic loading. The influence of shear reinforcement ratio of the composite columns was investigated as well. Then, a finite element analysis with the software of ATENA was carried out to obtain the optimal height of the ECC layer in the ECC/RC composite column. The mechanical behaviors of RC short column, ECC short column and ECC/RC composite short columns with different heights of ECC layers under combined vertical and horizontal loading were comprehensively studied and compared. The experimental results indicate that the use of ECC in the column bottom can change the failure mode from brittle flexure-shear failure to ductile flexure failure mode. The ECC and ECC/RC composite short column are extremely similar in seismic performance, and have superior ultimate load capacity, ductility and energy dissipation capacity to the RC short column. Due to higher shear strength, ECC can partly replace stirrups and reduce the stirrup ratio of ECC/RC composite short column. The simulation results show that the ECC/RC composite short column, where the ECC layer is 0.8h (h is the depth of the column section) height, can achieve similar mechanical properties of ECC short column. And the ECC zone in this composite column is just the plastic hinge regions of the RC short column. 9th International Conference on Fracture Mechanics of Concrete and Concrete Structures FraMCoS-9 V. Saouma, J. Bolander and E. Landis (Eds) DOI 10.21012/FC9.142 Li Xu, Jinlong Pan and Jingming Cai