Effect of fling-step removal in near-fault earthquakes on multi-story buildings

Abstract

Near-field earthquakes have two important effects, Forward Directivity and Fling-step, in which Forward Directivity depends on the direction of occurrence of an earthquake, and Fling-step happens due to permanent displacement of the earth due to tectonic deformations and its integration with the tearing mechanism with a velocity pulse with high amplitude and a uniform step in the displacement time history. Considering that few studies have been done on the effects of fling-step on structures other than Forward Directivity, and also in most earthquake data centers, all earthquakes are filtered using filtering methods and the fling-step effect is eliminated, therefore, four types of 4, 8, 12 and 16-story structures are selected and are designed based on the American Seismic Code (ASCE-10), in accordance with the American Steel Regulation (AISC341-10), in accordance with all the criteria for steel special moment frames. 16 records having fling-step effect are selected and applied to the structures. Also, to show effect of neglecting the fling-step on the response of the structures, the same records having no fling-step are applied to the structures and compared to the unfiltered state. The results showed that fling-step has little effect on the structure response, and filtered records can be used on seismic analysis.

Keywords

• fling-step
• forward directivity
• near-field earthquake
• special steel moment frames
• displacement