The influence of forward-directivity pulse-like ground motion orientation angles on structural collapse capacity

Abstract

Near-fault ground motions typically exhibit significant directivity effects, which significantly influence the structural response and collapse capacity. This study examines forward-directivity pulse-like ground motions, assessing how various orientation angles influence the collapse capacity of structures. To ensure the consistency of ground motion time histories from varying orientation angles during an earthquake, the Directionally Consistent Sa_c value (DC-Sa_c) is proposed, based on the Sa (T₁,5 %) value indicative of structural collapse (Sa_c). Building on this metric, the study further explores the collapse capacity of 3-story, 9-story, and 20-story steel frame structures, as well as 3-story RC structures, under ground motion excitations at varying orientation angles. The study reveals that as the angle between the ground motion and the fault strike increases, the destructiveness of the ground motion intensifies, whereas the collapse capacity of the structures decreases linearly.