Concorde Overpass Collapse: Structural Aspects

This paper describes the structural aspects of the collapse of the Concorde overpass, crossing Autoroute 19, in Laval, north of Montréal. The original design and the reinforcing details for the thick cantilever slab that failed are discussed. Results from testing a simulated portion of the bridge with as-designed and as-built details are presented. The structural analysis results, by using various bridge design codes to determine the design forces, are compared. The results from nonlinear finite-element analysis, simulating the concrete deterioration, are used to explain the cause of failure of the thick cantilever slab under essentially its self-weight after 36 years in service.