Seismic assessment of RC building frames using direct-displacement-based and force-based approaches

The conventional force-based design (FBD) method has been in practice for seismic assessment of RC building frames. In the FBD method, the main focus is on the seismic forces over the structure. In recent years, various shortcomings have been pointed out by research works, for example assumed initial stiffness of structural components, inappropriate response reduction factors, etc. To overcome these limitations of FBD, many new techniques have been developed and implemented. One such method is the direct-displacement-based design (DDBD) method. In this, the basic assumption is that strength is less critical than displacement. DDBD is a design theory in which design criteria are articulated for achieving a specified level of performance goals that are subjected to the defined level of seismic hazards. In this paper, the vulnerability of buildings situated in high seismic regions in India has been assessed. Four- and eight-storey RC building frames are taken into consideration. The non-linear time-history analysis is carried out, and the inelastic behaviour of buildings in the form of base shear, inter-storey drift ratio (ISDR) and maximum displacement is assessed. Also, fragility curves have been developed considering the effect of ISDR. It is concluded that the DDBD approach is more reliable and efficient for designing RC building frames as compared to its counterpart FBD approach.