Unified Performance-Based Design of RC Dual system

Abstract

A dual system building is comprised of frames and shear walls. In dual system the shear wall predominantly carries the lateral loads arising out of earthquake or wind. Frame is primarily designed for vertical load along with a fraction of lateral load. The force-based method of design or codal design method can hardly design building for pre-defined target objectives. The alternative method of design is displacement-based design (DBD). Available displacement-based design, like, Direct Displacement-Based design (DDBD) had been applied to dual system. However, DDBD method satisfied only drift criteria and was silent about the performance level. Also, the member sizes had to be obtained through iterations. Unified Performance-Based Design (UPBD) method can accommodate both drift and performance level as target design criteria. In the present study the theoretical background of UPBD method for dual system has been explained and detailed design steps have been highlighted. The method has been validated through several dual system buildings with different target design criteria. Dual system buildings have been designed using UPBD method for target objectives of (i) Immediate Occupancy performance level (PL) with drift 1%, (ii) life Safety PL with drift 2% and, (iii) Collapse Prevention PL with drift 3%. The nonlinear evaluation of the designed buildings shows that in all the cases the target design criteria have been fulfilled. The UPBD method of dual system also gives the member sizes in the beginning of the design and thus avoids iteration in design.