Seaspan Outfitting Pier Case Study: Soil Structure Interaction Analysis

Abstract: A new outfitting pier is currently under construction at the Vancouver Shipyards located in North Vancouver, British Columbia to support the fabrication and assembly of a number of vessels including the Joint Support Ship (JSS) which is the largest in the Royal Canadian Navy, as part of the Government of Canada's National Shipbuilding Strategy. The project is being led by Seaspan with construction by Fraser River Pile and Dredge (FRPD), design by Stantec, project management by Projectwise, and consists of the replacement of an existing 155m long by 10m wide timber structure built in 1966 with a new 272m long by 19.2m wide steel pile and concrete deck structure. The new structure is located in one of the highest risk seismic zones in Canada and a key design challenge was analyzing the soil structure interaction to account for a 35m thick liquefiable layer of subsurface soils which resulted in driving piles over 50m deep which will be verified by PDA testing. The pier is also designed for a 220 tonne mobile crane, 10 tonne tower cranes, and a CL-625 design truck per the bridge code. Due to the environmental constraints involved with the site location, the pier has a unique deck drainage system that fully collects the storm drainage and pumps it back to shore for safe disposal away from the marine environment, including consideration of sea level rise and extreme storm surge events. This paper will present a comprehensive overview of the analysis of the Outfitting Pier, including both geotechnical and structural aspects, with an emphasis on the advanced analytical techniques and collaboration between both disciplines.

How does this project / topic contribute to the advancement of the industry and profession?: This topic can help advance the engineering profession by sharing insights into better understanding pile behavior with respect to soil structure interaction and how seismic resilience was addressed, as well as design optimizations to help save time and cost of the project. Overall this paper will aim to contribute to knowledge dissemination, practical guidance, and improved engineering practices for soil structure interaction of deep pile foundations in liquefiable soil conditions.

Does the project / topic implement new and innovative techniques, materials, technologies, and delivery methods?: Our in-house geotechnical and structural design teams collaborated closely during detailed design development to perform advanced analyses of the pile and deck structure for both gravity loads and extreme seismic loads, including a significant liquefiable layer identified in the subsurface conditions that required deep pile foundations. Multiple iterations were required in the analyses to simulate reasonable pile behavior and achieve target displacements for the structure performance. The structural analysis models were calibrated closely with geotechnical engineering inputs for soil spring parameters, and design assumptions were validated on site through PDA testing of in situ piles.

What was the most challenging aspect of your project / topic and how did you handle it to ensure success?: The accelerated delivery schedule presented many challenges for the project, which were overcome with close coordination between the design team and construction team, early procurement of pile supply, and fast tracking techniques utilized by the contractor. The in-house collaboration between engineering disciplines (i.e. structural, geotechnical, drainage, electrical, mechanical, etc.) and close coordination with our environmental permitting / regulatory team offered advantages during detailed design development to meet accelerated timeframes.

Who is the target audience for this paper?: Engineering colleagues, environmental scientists, port authorities, terminal operators, marine contractors, and other industry professionals will be interested in this case study given the technical complexities, accelerated schedule, and site challenges that were overcome.