Alexandra Bridge Deck Rehabilitation and Seismic Retrofit

In 2009, Associated Engineering carried out a detailed condition and renewal options assessment and recommended rehabilitation of the bridge. Following this, we carried out the rehabilitation design of the structure.

We first conducted a detailed bridge inspection including a visual inspection of all accessible components using a bridge inspection truck for access below deck level. The inspection identified that the steel approach span girders and arch steelwork were in fair condition with minor corrosion; however, the concrete deck had significantly cracking and delamination.

Following the investigation of renewal options and life cycle cost analysis, we developed a renewal scheme that incorporated a partial-depth concrete deck overlay to address concrete deterioration and widen the roadway deck to 12 metres. Our assessment indicated that continuous deck diaphragm action was necessary to eliminate seismic vulnerabilities. This involved re-articulation of the approach spans and installing link decks across the breather joints near the arch crown.