SEISMIC PERFORMANCE ASSESSMENT OF CONCRETE MOMENT-RESISTING FRAMES WITH CONSTRUCTION ERROR AGAINST NEAR-FAULT STRONG GROUND MOTIONS

Man-made structures have always been subjected to construction errors. Although improvement of construction techniques decreases the mentioned errors; however, to achieve the reliable results regarding seismic performance of structures construction errors must be involved. Seismic performance assessment of sampled moment-resisting concrete frames with construction error is considered as the first goal of this paper. Besides, as the second goal, effects of near-fault strong ground motions on seismic performance of the sampled frames are studied. To achieve the mentioned goals, three concrete moment-resisting frames with 4, 6 and 10 stories has been designed according to the national seismic design code (Standard No. 2800). Nonlinear modeling of the sampled frames was implemented assuming the concentrated plasticity model by OpenSEES tool. The hysteretic formulation of the concentrated hinges is based on Modified Ibarra-Krawinkler (Ibarra et al., 2005) hysteretic model. The modeling parameters have been verified based on relevant experimental results (Haselton et al., 2016). To involve the effects of construction errors, three scenarios are considered. These scenarios consist of frames with no construction error (with no initial drift); columns initial drifts equal to the allowable construction tolerance and columns initial drifts larger than the allowable construction tolerance. The modeled frames for each scenario have been excited with two sets of strong ground motions, which consist of 20 near- and 20 far-fault events. Probabilistic seismic demand model (PSDM) shows the structural demand probability distributions against various strong ground motion intensities. The PSDM corresponding to the design-level intensity is used as the indicator of the seismic performance of the sampled frames. Therefore, the structural time-history analyses are implemented against the strong ground motions which are scaled to the design intensity. For instance, the cumulative probability distributions of structural demand (Maximum Inter-story Drift Ratio (MIDR)) for the 4-story intact frame are shown in Figure 1. The allowable MIDR is shown by the vertical green line. The corresponding probabilities show the probability of MIDR being less than the allowable threshold, which is used as the indicator of seismic performance of structure. Similarly, the relevantprobabilities are presented in Table 1 for the sampled frames and various construction error scenarios.

Keywords:

Near-fault strong ground motions , Concentrated plasticity model , Non-linear time history analysis , Fragility curves , Seismic Performance