Influence of Steel Section Configuration on the Seismic Performance of Concrete-Encased Steel Rectangular Bridge Piers

Featured Application: Optimized concrete-encased steel (CES) bridge piers offer a high-ductility, energy-dissipative solution for seismic-resistant bridge design in Canadian conditions. Concrete-encased steel (CES) bridge piers can be considered as a robust alternative to traditional reinforced concrete sections, especially in regions prone to seismic activity. CES piers combine the ductility of steel with the compressive strength of concrete, offering improved energy dissipation and resilience during earthquakes. Given the lack of CES design specifications in the Canadian design code, it is crucial to compile a body of knowledge describing the behavior of the CES bridge pier in order to facilitate the codification of the design guide. This study assesses the seismic performance of CES rectangular bridge piers with a focus on how variations in the steel section configuration affect the pier’s overall behavior under seismic loads. To conduct this assessment, a fiber element model was employed to model CES bridge piers subjected to seismic loading. The thickness and height of the web and the width and the thickness of the flanges of the I-shape steel section were varied to understand their impact on the bridge’s seismic performance. In addition to the I-shape sections, a crossed two-I-shape section was also studied. Spectral analysis, nonlinear pushover analysis and nonlinear time-history analysis was performed on the bridge models in order to better understand the seismic performance of the studied bridge piers. Simulation results indicate that larger flanges increase the pier’s bending moment capacity, allowing it to absorb greater seismic energy and undergo larger deformations without failing. This increases the overall ductility of the pier and enhances its ability to dissipate seismic energy. However, excessively large flanges or web can reduce the concrete cover and reduce the durability of the pier in the context of Canadian extreme-winter conditions. The study concludes that a balance between web thickness and flange width must be achieved to ensure the bridge can resist seismic forces while maintaining sufficient ductility and energy dissipation. Therefore, an optimized design, according to seismic demands, enhances the overall resistance of CES bridge piers.