Abstract Manager

The Royal Avenue Underpass rehabilitation was part of the City of New Westminster roadwork and structure improvements portion of the overall design-build Pattullo Bridge Replacement Project. Originally designed and constructed in 1954, the structure had exceeded its design life, had durability issues, and did not meet the current seismic design requirements – but was essential infrastructure for the drivers of the 65,000 vehicles per day that crossed the structure.

While complete replacement of the underpass (or at a minimum the superstructure) with a new concrete structure would have been the conventional approach to meeting the design requirements, that approach would have resulted in lengthy road closures and traffic disruptions, and presented environmental concerns as both the demolition and production of concrete result in significant greenhouse gas (GHG) emissions. Through careful investigation and design, Hatch was able to work towards net zero infrastructure objectives in rehabilitating the underpass to meet current seismic standards and project durability criteria, salvaging the original abutments, wingwalls, and approach embankments.

In order to meet current seismic standards, the original cantilever abutment walls were rehabilitated and thickened, including additional front face reinforcing to accompany a change in structure articulation. The new superstructure is fixed to the top of both abutment walls using large cast in anchors, and acts as a prop to stabilize the abutment walls against seismic earth pressures.

The new superstructure was completely assembled off site, and moved into place using a Self-Propelled Modular Transporter (SPMT) for removal and replacement of the superstructure during a single weekend traffic closure. This approach resulted in significant reductions in the use of heavy equipment, reduced concrete demolition and production, and avoided the increased commuter travel times resulting from lengthy detours.

This methodology was successfully implemented on a significantly deteriorated structure in a densely populated area with high seismic demands, and is highly adaptable to many other applications.