Abstract
Near-fault ground motion can be identified by the presence of a predominant long duration pulse in the velocity traces mainly due to directivity effect. This pulse exposes the structure to high input energy at the beginning of the earthquake which leads to a higher response in comparison with the ordinary ground motions. This paper investigates 79 earthquake records with different properties to achieve three goals: the first aim is to compare between the linear and nonlinear response of SDOF systems under near-fault and far-fault earthquakes. While the second objective is to examine the parameters that control the characteristics of near-fault earthquakes. Two factors have been studied which is PGV/PGA ratio and pulse period. Finally, the seismic code provisions related to the near-fault earthquakes were evaluated in term of the elastic acceleration response spectrum, the evaluation is adopted for American Society of Civil Engineers code ASCE 7 and Uniform Building Code UBC. The results lead to the following conclusions: with respect to a specific PGA, the near-fault earthquake imposed higher response in comparison with far-field earthquakes. The near-fault earthquakes become severe as the PGV/PGA and pulse period increase. The interested seismic codes can cover the actual behavior based on the average response of a certain amount of data, while it may become non-conservative relative to an individual record.
Highlights
Near-field earthquake identified by limited frequency and high amplitude pulse with a long duration that may or may not appear in the acceleration time history but it is significantly obvious in the velocity traces
It is noted that the previous attempts are dealing with a relatively limited number of ground motions to investigate a specific case study which normally leads to conditional results
It is important to perform comprehensive investigation including a wide range of near-fault earthquakes that has different characteristics such as fault mechanism, site condition, PGA and magnitude
Summary
Near-field earthquake identified by limited frequency and high amplitude pulse with a long duration that may or may not appear in the acceleration time history but it is significantly obvious in the velocity traces This kind of ground motions put the structures under high input energy at the starting of earthquake due to the effect of two phenomena called directivity effect and fling step effect. By examining a set of earthquakes with and without pulselike which has equivalent acceleration response spectrum shapes He noticed that the severity of the near-fault earthquakes cannot be predicted only by the shape of the spectrum and it's important to investigate deeply the pulse properties which have the major effect on the intensity of the ground motion [9].
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