Abstract Manager

In August 2022, a transport tanker carrying a highly flammable liquid crashed into the approach barriers at the Sikanni Chief River Bridge resulting in a full closure of Hwy 97 in northern BC. The fire generated intense heat that resulted in extensive structural damage and brought forward severe concerns for weakening of the bridge. As a lifeline Highway, and critical link to Northern Canada, there was extreme pressure to get this Highway safely re-opened as quickly as possible.

An emergency response was initiated immediately with a rapid damage assessment that enabled light vehicle traffic to be restored shortly after the incident. The emergency response and structural assessment continued until full unrestricted truck traffic was restored on the bridge. While the primary focus was forensic review and structural evaluation for load rating, several concurrent bridge engineering teams were mobilized to work in parallel to develop contingency plans that were on hand in case the structural evaluation determined insufficient capacity for truck traffic to be restored. Concurrent Teams completed forensic review; load testing; structural evaluation for load rating of the bridge in its damaged state; detour planning; fibre-reinforced polymer strengthening detail design; and external strengthening detail design.

For the structural evaluation and load rating, destructive and non-destructive testing was performed along with petrographic examination of the concrete to determine heat profiles throughout the reinforced concrete bridge deck and within the prestressed concrete girders. Prestressing strands, mild reinforcing steel, and concrete cores were all extracted from the bridge for testing. Strengths results were adjusted for heat profiles determined from the petrographic examination and were then used for structural capacity determination of the bridge in its damaged state. Load testing results were used to validate a 3D Finite Element Model of the bridge to accurately determine structural demands. The structural evaluation and load rating determined that the structure had sufficient capacity in its damaged state for unrestricted loading and the bridge was re-opened to full legal truck traffic 24 days following the incident.

This presentation highlights key lessons learned when responding to fire/heat damaged structures and what to triage and prioritize in the response.