Dariush Alimohammadi - M.Sc., Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran
Esmaeel Izadi-Zamanabadi - Assistant Professor, Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran

In this study, the effect of using two seismic design approaches, direct displacement based design (DDBD) and traditional force based design (FBD), on the probabilistic seismic performance of an 8-story RC moment resistant building is investigated based on reliability framework. Two probabilistic methods namely assessment by considering the only source of uncertainty and assessment by considering randomness and uncertainty as the sources of uncertainty are used. This research is conducted using the results of incremental dynamic analyses by studying (i) the mean annual frequency (MAF) (ii) seismic demand of limit states (iii) the confidence level of structures under the earthquakes with low to high hazard levels. For this purpose, an analytical model was developed in OpenSees framework environment based on experimental results. The results show that considering aleatory and epistemic uncertainties in the probabilistic seismic performance evaluation can increase the MAF of exceeding the immediate occupancy (IO) and collapse prevention (CP) and thus make the structure more vulnerable. In addition, the MAF has increased significantly by moving from DDBD to FBD approach and the adequacy of DDBD design approach in structural seismic design is demonstrated. Estimating the confidence level variations vs. the maximum drift demand and earthquake intensity, provide the conditions to access different values of demand and confidence level corresponding to different hazard levels. Consequently, the effect of using two DDBD and FBD design approaches on the seismic performance of the studied structure can be determined. It is shown that the structure designed with FBD, unlike DDBD approach has a very low confidence level at high seismic hazard levels and exhibits poor seismic performance.

Direct Displacement Based Design, RC Frame, Incremental Dynamic Analysis, Probabilistic Evaluation,Confidence Level