Influence of different criteria for selecting ground motions compatible with IEEE 693 required response spectrum on seismic performance assessment of electricity transmission towers

Abstract

Electricity transmission towers are vital in minimizing the risk of disruption of power supply after earthquakes. However, no guidelines currently exist for seismic performance evaluations of electricity transmission towers. Considering electricity transmission towers should have the same desirable performance as electric substations, this research team assessed seismic performance of transmission towers using the Institute of Electrical and Electronics Engineers (IEEE) recommended document for seismic design of substations (IEEE 693). A representative existing system was identified as the prototype. A computer model was developed for Response History Analyses (RHA) of the prototype. Three suites of ground motions matching the IEEE 693 required response spectrum were considered, consisting of one suite of three pre-approved empirical and random records and another two suites of records selected based on different criteria. It was found that the prototype designed according to the equivalent static force method meets the qualification requirements of IEEE 693. Additionally, it was found that a filtered version of the pre-approved empirical record to accommodate the limitations of some shake tables do not always provide results consistent with the un-filtered record. Moreover, analysis results reveal that different historic records selected matching the same target spectrum cause different responses in the prototype, suggesting the need to consider variation of ground motions. Further, it was found that the artificial ground motions may not always be adequate for analyses of transmission towers depending on what criterion is used in record selection. Last, it was found that failure of the prototype is highly non-ductile and seismic performance of the prototype is very sensitive to the amplitude of the input ground motions.