The effects of steel fibers and boundary elements on the seismic behavior of high-strength concrete shear walls

Six shear walls using high-strength concrete and high-strength steels were studied by conducting cyclic load tests, including two reinforced concrete shear walls, and four composite walls reinforced by concrete-filled steel tubes (CFSTs). The effects of steel fibers and boundary element forms on the cyclic behavior of the walls were investigated. Research founds that the steel fiber reinforced specimens showed lighter damage degree, lower deformation capacity, and lower proportion of shear deformation than the non-fiber reinforced specimens. Among the three types of specimens with different boundary elements, steel fibers had the greatest influence on the composite walls with concrete-encased CFST columns in boundary zone. Compared the two types of composite walls reinforced by CFSTs which were designed by the principle of "equal vertical bearing capacity of the boundary elements", the walls with outer CFST columns showed better energy dissipation capacity than the walls with concrete-encased CFST columns. Finally, considering the stress characteristics and the constraint effect of boundary elements of different kinds of shear walls, the simplified calculation model of load-carrying capacity and the finite element analysis model were established and verified.