Lord Strathcona Elementary School: First Base Isolated Building in Canada

Assigned legal heritage designation by the City of Vancouver, Lord Strathcona Elementary School is one of British Columbia’s oldest continuously operating schools. Three of the five buildings on site were identified as requiring seismic upgrades.

Ausenco’s structural engineering team was brought in to assess, and to then bring the three buildings up to three unique levels of seismic performance: life safety; damage mitigation (post-earthquake occupancy); and operational/heritage preservation.

A variety of linear and non-linear analyses were employed to provide the most efficient retrofit solution for each of the three buildings.Two of the buildings were upgraded through conventional upgrading methods (external concrete buttress walls, internal concrete shear walls) while the third – a load-bearing unreinforced brick/stone building was upgraded using seismic (base) isolation technology.

Completed in December 2016, this represents the first base isolated building* in Canada (new or seismic upgrade). [*occupied building; some very small unoccupied new mechanical control units have been installed using base isolation.]

Critical success factors incorporated into the project execution include:

• an extensive material testing program to confirm the capacity of the original structures and to obtain geotechnical parameters
• extensive sensitivity analysis to account for variations in existing building components and soil-structure interaction behavior
• re-analysis of the base isolated structure using as-tested parameters of both the lead core rubber bearings and the teflon-stainless steel sliders
• specialised remediation of unique building components not identified in the material testing program.

Jacking and load transfer of the base isolated building was key to the success of the project; this was completed while maintaining the elevation at the isolation plane within 3 mm of the original as-constructed level.