Performance of Force Based Design Versus Direct Displacement Based Design in Predicting Seismic Demands of Regular Concrete Special Moment Resisting Frames

Abstract

As an approximate method in seismic design, direct displacement based design (DDBD) has been widely accepted in conjuction with the former method, force based design (FBD). In its procedure FBD uses building displacement as the final check to determine the structural performance while DDBD use it as the designed target performance. If the final displacement in FBD larger than the value specified by the standard then the design procedure should be recalculated. On the other hand, under some common practices the procedure of DDBD is more straight forward compared to FBD. Unfortunately, the prospective use of DDBD is not applied well, especially in Indonesia. Therefore, the objective of this study is to evaluate the performance of DDBD on a regular concrete special moment resisting frame compared to two varians of FBD, equivalent lateral force procedure and response spectrum analysis. All methods are designed using the latest Indonesian seismic code and verified using the exact method nonlinear time history analysis. All design method are run in a single cycle of design without any effort to improve the performance level to experience the effectiveness of the each metod in predicting seismic demand. The parameters used for evaluating structural performance are story drift, damage indices, and structural failure mechanism. As the results, DDBD performed better than FBD in predicting story drift. All methods experience excellent damage indices level. Although all methods show tendency poor mechanism, DDBD needs no improvement because the structures fulfill the targeted peformance while FBD needs extra effort to improve the structural performance due to the design procedure should be repeated from the beginning. In this point of view, DDBD procedure is more effective compared to FBD.