Seismic Performance of RC Split-Foundation Frame Structures with Steel Braces in the Mountainous Area

Abstract

Reinforced concrete (RC) split-foundation frame structures are widely used in mountainous areas. There are two grounding terminals with different heights in the split-foundation frame structures. Under the earthquake, the local damage phenomenon of the structures is severe due to the uneven stiffness distribution. It is one way to improve the seismic performance of the split-foundation frame structures to install steel braces in the upper embedding floor. According to the deformation characteristics of the upper embedding floor, three types of steel braces arrangement for the split-foundation frame structures were proposed: horizontal braces, V-type braces, and V-[Formula: see text] braces. Then based on the ratio of lateral stiffness of steel braces and concrete frame columns, the section of steel brace was designed. A quasi-static test was carried out to analyze the influence of steel braces on the failure mode of the RC split-foundation frame. The reasonable seismic waves were selected to carry out the nonlinear dynamic time history analysis. Then the seismic response and failure mode of the split-foundation frame structures with different braces arrangements were compared. On this basis, fragility analysis was carried out, and the earthquake-induced collapse resistance capacity of split-foundation frame structures with steel braces was preliminarily evaluated. The results show that the horizontal steel brace can improve the phenomenon of damage concentration of the split-foundation frame structures. Furthermore, setting V-shaped braces can significantly reduce the damage degree of the upper embedding end columns and change the phenomenon of locally severe damage of the split-foundation frame structures. Moreover, according to the design method proposed in this paper, setting steel braces can improve the seismic collapse resistance capacity of the split-foundation frame structures.