near-fault effects on the seismic demand of rc buildings in linear and nonlinear analyses

Strong ground motions of nearfault earthquakes are mostly generated by forwarddirectivity effects. forwarddirectivity effects develop energetic pulses particularly in horizontal velocity history of faultnormal component. the narrowband nature of the pulses results in revealing at least two peaks on the response spectra and also increasing seismic demand especially for midrise and highrise buildings. iranian seismic code (is 280014) presents the coefficient n, for considering nearfault effects. it seems that the n is not efficient for designing in nearfault zone. the accurate nearfault demands can be determined by using nonlinear response history analyses. in the present paper, two 3d reinforced concrete framed structures (rc buildings) are designed according to aci 2014 and is 280014. then, the demands are estimated by employing linear response history analysis (lrha) and also nonlinear response history analysis (nrha) under an ensemble of 11 nearfault ground motions. the results reveal that the design spectrum of is 280014 is incompatible with nearfault spectra and underestimates demands in the long periods range. further, implementation of lrha using response modification factor (ru) and deflection amplification factor (cd) leads to insufficient interstory drift ratios. finally, the influence of enhancing ductility is studied by determining ductility reduction factors for nearfault records.