2019 CSCE Annual Conference - Laval (Greater Montreal)

2019 CSCE Annual Conference - Laval (Greater Montreal) Conference


Title
BEHAVIOUR OF 27-YEAR OLD PRESTRESSED CONCRETE BRIDGE GIRDERS

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Author
Ms. Zhaohan Wu, University of Alberta (Presenter)
Abstract

Prestressed concrete is one of the favored construction materials around Alberta due to its better stiffness and cost saving than normal reinforced concrete. Recently a bridge on Highway 763, built in 1991, was found to be seriously deteriorated, so Alberta Transportation had to close the bridge. During subsequent inspections, it was also found that the material properties of these bridge girders are unclear. Questions arose immediately on how much loads these girders can carry before it actually fails. Since the code is relatively conservative; the design of these bridges are continually being pushed. Since the bridge is deteriorated, it is uncertain how much loads it can take before it fails. Alberta transportation turned to University of Alberta to help; the goal is to investigate the residual capacity of these damaged girders. The first stage of this project is to use the original properties of the damaged girder to calculate moment capacity of the “as new girder”. Later on experimental testing will be carried out on these 9 damaged girders to investigate the failure modes. Vector 2 is used to calculate the moment capacity of the original girders. This finite element modeling program can give reaction forces as an output with a corresponding failure mode of the model. These girders will be transferred to University of Alberta structural lab. Each girder is under flexure cracking test to determine their actual capacity. All girders are simply supported on 4 steel pedestals with electrometric bearing pads. In order to achieve 4 points bending, a spreader beam is placed on top of the experimental girder to distribute the forces from hydraulic ram. The experimental result will be compared with the modeling data to see how the deterioration affected the capacity of these girders. The finite element modelling method showed a capacity of 1358KNm for the "as new girder". The girder fails in flexure and concrete crushed after steel yields. This capacity data provided by VecTor 2 gives a good understanding of how these girders will perform under testing. Experimental data will be available in December 2018 after testing these girders, so it can give a better perspective of the material properties and damages on the girders.