Earthquake response of large-span reinforced concrete structures with haunch braces under vertical ground motions

A new type of reinforced concrete (RC) frame system with diagonal haunch braces is introduced in a large-span sports education building. In this paper, the nonlinear dynamic responses of the large-span RC frame structures with diagonal haunch braces (RCFB) are studied under vertical near-fault pulse-like and non-pulse-like ground motions. Ten ground motions of the Chichi earthquake event are selected and divided into two groups. The large-span plane RCFB structure is simplified from a practical engineering structure and used to perform a dynamic time-history analysis. The vertical mid-beam displacement and the axial pressure at the base of the bottom column of the structure are compared under vertical pulse-like and vertical non-pulse-like ground motions, and the effects of the structural system parameters on the vertical mid-beam displacement are analyzed. This study shows that the vertical earthquake response of a large-span RCFB structure is significant, especially under pulse-like ground motions, and that the structural system parameters and the impulsive effect of ground motion exhibit a distinct coupled effect on the vertical response. Optimizing the location of haunch braces is very critical in RCFB structural design.