Evaluating the effects of near-field earthquakes on the behavior of moment resisting frames

Following the 1994 Northridge and 1995 Kobe earthquakes, most of modern structures damaged seriously or devastated totally despite the seismic codes of these countries that had been expected to bear advanced criteria for seismic design of structures. After extensive research, the most probable reason of those destructions was attributed to special specifications of near-field earthquakes. In this paper, in addition to a brief review on the special characteristics of near-field earthquakes, using actual records of these ground motions and pulse like inputs simulating near-filed records, the effects of this type of earthquakes on the distribution of the maximum shear force and flexural moment demands are evaluated. Results show that the response is very sensitive to the ratio of natural period of structure to the governing period of ground shaking pulse, such that, in some cases it leads to increasing force demand ratios of structure and even transmitting its centroid to upper stories.