Shear Strengthening Using Frp Sheets for a Idghw a Y Bridge in Manitoba, Canada

The use of heavier trucks demanded upgrading of a twenty-seven year old bridge in Winnipeg, Manitoba, Canada. Analysis of the precast prestressed concrete girders using the current AASHTO Code indicates a deficiency in the shear capacity. Shear strengthening using Carbon Fibre R_einforced Polymer (CFRP) sheets provides a low-cost solution by increasing the speed of construction and reducing traffic interruption when compared with conventional methods. Due to a lack of information on the use of CFRP sheets for shear strengthening of I-shaped concrete AASHTO girders, an experimental program has been undertaken at the University of Manitoba. Four ten meter long scale model prestressed concrete girders have been tested to failure at both ends, using six configurations for three types of CFRP. The contribution of the CFRP sheets to the enhanced shear capacity of the girder has been evaluated. This paper presents preliminary conclusions and recommendations for the use of this strengthening technique on this particular girder shape. INTRODUCTION The city of Winnipeg, Manitoba, Canada, is considering an upgrading of the Maryland bridge in response to the demand for using increasingly heavier truck loads. The twin five-span continuous prestressed concrete structures were designed in 1969 according to the American Association of State Highway and Transportaion Officials (AASHTO) Code. Rehabilitation analysis using the current AASHTO Code indicates that while the flexural strength of the I-shaped girders is adequate, the shear strength of the girders is not sufficient to withstand the increased truck load. Carbon Fibre Reinforced Polymer (CFRP) sheets provide an excellent solution for shear strengthening since they are light-weight, corrosion-free, and have a high tensile strength. When compared with conventional methods, this technique provides a low-cost solution due to significant reduction of construction time without traffic interruption. Due to a lack of information on the use of CFRP sheets for shear strengthening of I-shaped concrete AASHTO girders, an experimental program has been undertaken at the University of Manitoba, Canada, to test scale models of the Maryland bridge girders strengthened with CFRP sheets. Four prestressed concrete beams are tested to failure at each end to determine the most efficient strengthening scheme. This paper summarizes preliminary test results and recommendations for the use of this strengthening technique on this particular girder shape. EXPERIMENTAL PROGRAM F our prestressed concrete girders were tested at the University of Manitoba, Canada. The ten meter long beams are 1:3.5 scale models of the I-shaped Maryland bridge girders. All of the beams had a depth of 4!5 mm with a top slab of 480 mm wide and 60 mm deep as shown in Fig.! and Fig. 2. The slabs were casted a minimum of seven days after the casting of each beam. The beams were pretensioned with three 13 mm straight steel 7-w;re strands and one draped strand. I~ 480