Effect of incident directionality on seismic responses and bearing capacity of OLF1000

Abstract

As a typical and important supporting structure in ultra-high voltage substations, the 1000 kV outgoing line frame (OLF1000) bears the role of supporting electrical equipment and long-span transmission lines. The interaction between transmission towers, lines and OLF1000 makes it exhibit asymmetric stress and deformation states in normal use. For this kind of irregular coupling system (i.e., OLF1000-tower-line coupling system), the seismic incident directionality effect (SIDE) with high uncertainty may be a disadvantage. To investigate the effect of incident directionality on the seismic responses and ultimate bearing capacity of the OLF1000, and provide a reference for its seismic design, this study numerically evaluated the seismic responses of the OLF1000 by considering the dynamic coupling effect between a tower-line system and OLF1000 (DCE-TLS-OLF1000) under 40 multi-direction ground motions. According to our results, the seismic incident directionality significantly affects seismic responses, participation of vibration modes, plastic development law, failure modes, and ultimate bearing capacity of the OLF1000. In contrast, traditional approaches (i.e., 0° directional excitations) cannot ensure the seismic safety of the OLF1000 in arbitrary incident direction as the guarantee rate is less than 50%. Furthermore, the direction-to-direction (DTD) and record-to-record (RTR) uncertainties were theoretically derived; moreover, 95% guarantee models based on the two uncertainties and prediction models by considering the DCE-TLS-OLF1000 and SIDE were proposed to ensure the seismic safety of the OLF1000 under excitations exhibiting arbitrary incident direction and provide a helpful seismic design method for designers.