Parametric study for long-span roof truss subjected to vertical ground motion

Abstract

Generally in the seismic resistant design of structures, effects of horizontal ground motions are mainly considered and effects of vertical ground motions (VGMs) are ignored. However, considering the field evidences of damage of structures due to vertical component of ground motion for near-fault earthquakes, the importance of inclusion of effect of vertical component of earthquake in seismic design has been recognized. Therefore in this paper, a parametric study has been carried out on 25 m long-span industrial steel roof truss with the help of 12 near-fault ground motions without pulse. The parameters related to roof truss as well as an earthquake data are studied to get the response of long-span roof truss under vertical ground motion (VGM) with nonlinear time history analysis using SAP2000V19.2.1 software. From the parametric study, it has been realized that for a chosen long-span industrial roof truss, the parameters such as vertical to horizontal peak ground acceleration ratio, axial force, vertical displacement and base bending moment are identified as critical. From the time history analysis results, it is also found that response of truss under vertical ground motion is critical for ground motions having V/H ratio more than 1 and therefore the long-span structure in near-fault zone should be considered separately in design rather than taken as 2/3 of horizontal acceleration as per given in IS1893:2016 (Part-1).