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UBC Theses and Dissertations

Critical seismic performance assessment of concrete bridge piers designed following Canadian Highway Bridge Design Code Kabir, Md Rashedul


Performance-based design (PBD) method is gradually taking over the traditional force-based design (FBD) for designing bridges in North America. Considering the importance of bridge structures in the transportation network, quantitative performance criteria were adopted in Canadian Highway Bridge Design Code (CHBDC) in 2014 and a supplement to CHBDC 2014 was published in 2016. In this study, a lifeline bridge pier is designed following the FBD method from CHBDC 2010 and PBD approach following CHBDC 2014 and the supplement to CHBDC 2014 to understand the impression of changes in bridge design codes. The dominating performance criteria in the new supplement to CHBDC 2014 for a lifeline bridge is the maintenance of repairable damage at a seismic event of 975 years return period. The performances of the designed bridge piers are assessed using 20 near-fault ground motions through incremental dynamic analysis. Fragility curves for the bridge piers are plotted to perform the seismic vulnerability analysis of the bridge piers designed following three different alternatives. A lifeline bridge pier is also designed following PBD from CHBDC 2014 using different ASTM grade steel of varying strength and fracture elongation in combination with different concrete strength. Performances of the designed bridge piers are evaluated for site-specific ground motion suits. Moreover, the impact of changing reinforcement strength on the designed bridge piers' seismic behavior is checked by fragility analysis. PBD from the supplement to CHBDC 2014 shows the highest damage probability. Whereas, the FBD from CHBDC 2010 and the PBD from CHBDC 2014 substantially reduce the risk of damage and improve the performance of the bridge pier. Practicing high strength steel reinforcement (HSR) in PBD of bridge piers can reduce the required percentage of reinforcement by 50% compared to conventionally used Grade 60 reinforcement. Construction difficulties can be avoided due to less congestion of rebars and cost of construction can be cut down without compromising the seismic performance. Damage vulnerability related to longitudinal steel strain reduces remarkably, and the collapse performance decreases when HSR are practiced in the design of bridge piers. Incorporation of high strength concrete can marginally improve the collapse performance.

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