Seismic response and joint fragility of UHV long-span truss structures with PGA and duration as variables

Abstract

To improve the seismic design of long-span truss structures (LSTSs, supporting-equipment structures) in ultra-high voltage substations and evaluate their seismic risk, the responses, collapse performances, and fragilities of LSTS considering peak ground acceleration (PGA) and duration as variables are examined in this study. The nonlinear finite element model of LSTS-tower-line system is established by considering the tower-line dynamic interaction, and it is excited by 17 far-field ground motions having varying durations (i.e., significant durations, DS90). Seismic responses of LSTS increase linearly with increasing DS90, and more significantly under earthquakes with a higher intensity. The duration effect on LSTS responses consists of excitation-amplifying and damage-cumulating effects, which leads to that the increasing DS90 accelerates the development of plasticity in LSTS subjected to major earthquakes, and thus reduces its collapse load in a nonlinear manner. The displacement-based and IM-based joint probabilistic seismic fragility methods are proposed by regarding the record-to-record, structure-to-structure, and duration-to-duration uncertainties. The fragility curves with DS90 as a variable and fragility planes with PGA and DS90 as variables are generated to provide an important reference for LSTS seismic risk assessment.