MEDICINE RIVER BRIDGE REHABILITATION

The Medicine River Bridge is located in central Alberta on Highway 11, midway between Red Deer and Rocky Mountain House. The bridge is a three span cast-in-place concrete girder bridge constructed in 1954. It has a clear roadway of 8.5 metres. With traffic volumes in the order of 5000 AADT the bridge is an important link for local commuters to Red Deer and for oilfield traffic to west-central Alberta. Two deficiencies were identified regarding the functionality of the bridge. First, the bridge’s load capacity was in question due to shear cracking of the girders and second, the narrow bridge clear roadway and out-of-date bridgerails were identified as being a safety concern. An assessment of the bridge and development of rehabilitation alternatives showed that bridge rehabilitation was more economical than bridge widening or bridge replacement. A load evaluation of the bridge was carried out in accordance with the Canadian Highway Bridge Design Code (CHBDC). This load evaluation showed that the girders were deficient in negative moment capacity but not in shear capacity. The girders were strengthened by attaching carbon fibre reinforced plates to the bottom of the bridge deck. The existing bridgerails were upgraded by mounting a new steel HSS rail in front of the existing bridgerail posts and in line with the existing curb roadway face. To protect traffic from the ends of the bridgerail the approach rail guardrail was securely fastened to the ends of the new HSS rails and locally stiffened to meet crash test requirements. Rehabilitation of the bridge was carried out in the fall of 2002. This paper describes the deficiencies identified in the Medicine River Bridge, the assessments carried out to select an appropriate rehabilitation strategy and the design and construction of the selected bridge rehabilitation strategy.