Numerical Analysis of Regular Reinforced Concrete Frames under Near-Fault Ground Motions

Near-fault earthquakes are more severe compared to typical ground motions which are used in most of the seismic design codes. Near-fault ground motions with forward-directivity and fling-step can be categorized as the two major types of these earthquakes that impose great demands on structures. This paper considers the effect of near-fault earthquakes on the different reinforced concrete frames which have been modelled based on up-to-date methods by comparing their responses with the ones under far-fault ground motions. Fourteen near-fault ground motion records with forward-directivity and fling-step characteristics and seven far-faults have been selected. Regular frames with 4, 7 and 10 stories are separated into two categories of reinforced concrete moment (RC) frame with and without shear walls. Nonlinear time-history analyses of RC frames have been performed using OpenSees software. In addition, artificial neural network approach is utilized to estimate a relationship between structural response and inherent characteristics of ground motions which illustrates the way each characteristics influences the structural response under different types of ground motion records. The results show that near-fault earthquakes considerably affect the response of both frames for all cases under different ground motion records as it increased the responses by 72 percent for the frames with shear walls, and by 45 percent for those without shear walls on average. Also, the effect of near-fault earthquakes becomes more significant as the number of stories increases. In case of records with fling-step effect, the difference in the behavior of frames with different height is shown to be more noticeable as in some 10 story cases the demands grew by 100 percent, while it was nearly the same in 4 story frames.