| This thesis report examines six decommissioned pre-tensioned concrete channel girders which were part of the Canadian National Railway overpass on the Trans-Canada Highway No. 1 (CN Overpass on TCH Site No. 0709-00) east of Portage La Prairie constructed in 1965. The six girders are representative of the various levels of deterioration observed on the in-service bridge.The primary objective of this research was to determine the remaining capacity of the 40 year old girders in flexure and shear when subjected to monotonic loading. Non-destructive testing was also carried out including material sample testing (concrete strength, air-void content and chloride ion content). Additionally, the girders were load rated using both the Canadian Highway Bridge Design Code: Bridge Evaluation and the American Association of State Highway Officials: Load and Resistance Factor Rating methods.Given the analysis of the data of the six girders that were comprehensively examined, their experimentally observed capacities surpassed the theoretical capacity on the order of 27 and 47 percent for bending and shear respectively. The concrete strength testing demonstrated an increase of 36 percent to that of the design value. The material tests revealed the cause of the deterioration of the girder webs was due to cyclic freeze-thaw affects.Using the experimentally observed moment and shear capacities allowed the CHBDC load rating method to achieve a favorable rating. However, the AASHTO LRFR method did not achieve a passing rating for all girders.In the summer of 2006, UMA Engineering Ltd. (now AECOM) was contacted by Manitoba Highways and Infrastructure to inspect the Trans-Canada Highway rail overpass. Several of the girders in the center span were said to be in poor condition. The webs had been subject to water leakage through the shear keys and concrete cover loss ranging from 25 mm to 100 mm from the bottom of the webs was observed.As a result ofthis research work it was recommended that research of pre-stressed girders be conducted to reduce the level of conservatism of flexure and shear capacities calculated within the Canadian and American design codes, that within Manitoba bridges of this nature should be load tested to increase the accuracy of the load rating analysis, and that post service bridge components be experimentally examined to narrow the gap between theory and qualitative analysis, and quantitative performance characteristics to increase the level of understanding and knowledge of bridge component reactions to expected service inputs. |
