Structural Monitoring of a Closure Strip in the Staged Construction of a Slab-on-Girder Bridge on Highway 401

Highway bridges are routinely rehabilitated or replaced in stages to avoid lane reductions. In recent years, the Ontario Ministry of Transportation (MTO) has seen an increase in inquiries and concerns from engineers and contractors related to staging. Some of the potential problems relate to settlement and movement of plastic concrete due to live load vibration, and shear and rotation at the construction joint, resulting in compromised reinforcement bond and reduced concrete quality at the construction joint. In support of a recent guideline advising designers of issues that shall be considered when designing bridges rehabilitated or replaced in stages, the MTO monitored the Hwy 401 Westbound Collectors Bridge over the Ramp from the Hwy 401 WBL Express to DVP/Hwy 404, during replacement. The paper describes the bridge’s behaviour as the closure strip concrete sets up. The relative ratio of strain between girders across the closure strip provides an indication of the development of load transfer over time.