Performance-based plastic design of composite partially-restrained steel frame-reinforced concrete infill walls with concealed vertical slits

In order to reasonably predict the seismic demand of composite partially-restrained steel frame-reinforced concrete (RC) infill walls with concealed vertical slits (PSRCW-CVS) subjected to the near-fault earthquake records with strong velocity-pulse effect, an innovative performance-based plastic design (PBPD) approach is developed in current study. The maximum effective cyclic energy (MECE), which can reflect this phenomenon that the structural dissipated input energy from near-fault pulse earthquake record commonly focuses on the largest yield excursion, is introduced and adopted as a new design indicator (ΔEh,max). The design base shear is determined according to the instantaneous energy balance concept and pre-selected desirable yield mechanism, which considers that the MECE demand obtained from MECE spectrum at target ductility ratio is equivalent to the instant energy supply from structural components. Additionally, the MECE calculating formula of each component of PSRCW-CVS structure is also provided. Four PSRCW-CVS illustrations (5-storey and 10-storey) with different target ductility ratio were designed according to the proposed PBPD methodology, and their seismic behaviors corresponding to the rare earthquake level were assessed through nonlinear time-history analysis method using the selected near-fault earthquake records with velocity-pulse effect. The analytical results show that four PSRCW-CVS structures can achieve the intended seismic behavior in terms of MECE, inter-story drift ratio, and residual inter-story drift ratio. The PSRCW-CVS structure exhibits the ideal progressively developed plastic mechanism. The reliability and reasonability of this PBPD method combined with MECE spectrum are verified, and it can be easily extended to other dual lateral load resisting systems.