Old concrete slab bridges. I: Experimental investigation

Old reinforced concrete slab bridges designed for smaller truck loads are called on to carry the modern, heavier, loads. These bridges, when rated according to the current American Association of State Highway and Transportation Officials procedures, are found to be structurally deficient. The present paper reports the experimental part of the investigation carried out to understand the behavior of this category of bridges, both at service and ultimate load levels in order to rate them more realistically. A five-span reinforced concrete slab bridge, built in 1938 and decommissioned since 1972, was tested destructively. The destructive test was performed by applying loads that simulated the presence of two trucks side-by-side on the bridge. Also, six three-span reinforced concrete slab bridges were subjected to service load tests. Two dump trucks, each weighing approximately 222.5 kN, were used to carry out the service load tests. Experimental results indicate that reinforced concrete slab bridges possess much higher strength than that indicated by current rating procedures.