ESTIMATION OF THE SEISMIC DEMAND AND CAPACITY OF RC BUILDINGS THROUGH INCREMENTAL DYNAMIC ANALYSIS

Abstract

In the last century major earthquakes have occurred in Albania and numerous buildings have suffered different level of damages. Throughout of its history it is observed that many important cities like Shkodra, Durrës, and Vlora have been destroyed due to severe earthquakes. Most of the buildings are designed according to earlier versions of Albanian Codes and several buildings were constructed without code provisions. Considering the fact that Albania is a moderate seismic country which has been hit frequently by the hazardous ground motions, establishes the need to assess the performance of the existing reinforced structures. The inelastic response of existing reinforce concrete (RC) buildings designed without seismic details is investigated, presenting the results from more than 1200 nonlinear analysis. The seismic performance evaluation is conducted for two buildings, three and seven story residential buildings, which represent the building block in Albania. The overall objective of the current study is to investigate the structural performance of low- and mid-rise RC buildings under seismic loading. For the purpose of this research, two performance earthquake engineering (PBEE) procedures are utilized: static and dynamic non-linear analysis also known as pushover and time-history analysis. Moreover, a new and modern procedure known as Incremental Dynamic Analysis (IDA) or dynamic pushover analysis, is considered for the seismic assessment of building models. Zeus-NL, a finite element analysis program, and SAP2000 are employed for the numerical analysis phase. In addition, a methodology is presented for the process and strategies followed up to generate the IDA curves by interpolation, the performance levels and finally the IDA fractiles. Afterwards, the structural performance under different loading condition is investigated using nonlinear procedures. Results are interpreted based on the code provision followed by FEMA 356. Moreover, capacity/demand ratios are followed to extend the interpretation of the structural behavior. Finally, a comparison between static and dynamic pushover curves is accomplished, in order to find correlation points among those curves. At the end, general conclusions and drawbacks are outlined while recommendation for further studies are suggested.