Performance-Based Seismic Design for the Vancouver Evergreen Line Rapid Transit Project—Process, Challenges, and Innovative Design Solutions

Performance based seismic design has emerged as one of the most rational methods to overcome inherent risks and uncertainties in predicting the seismic performance of structures designed by the force based approach. The Vancouver Evergreen Line Rapid Transit Project is a first known rapid transit project in Canada utilizing the multi-level performance-based design approach for the Guideway structures. The proposed Guideway alignment runs through enormously challenging site conditions prone to soil liquefaction causing variable, large-scale lateral spreading. Ground improvements were mostly precluded due to deep liquefiable layers coupled with a stiff crest near the surface, utility proximity and right of way issues. Innovative and robust structural solutions had to be developed to meet the performance criteria. Non-linear structural analyses incorporating soil-pile-structural interactions and directional ground deformations were carried out to confirm structural performance. As per the Project Agreement, the station building structures were designed based on the single-level and force-based design approach of the 2006 British Columbia Building Code, which presented additional challenges for the interface structural elements. This paper provides a summary of the seismic design criteria specified by the PA, seismic design review and approval process, technical challenges faced and innovative design solutions developed to meet the prescribed seismic performance criteria.