A proof test is described on a short-span reinforced concrete T-beam bridge without construction drawings, in the absence of which the bridge was posted by using only engineering judgment, to a maximum vehicle weight of 9t. A systematic proof test conducted with the help of controlled incremental loads, and some instrumentation, confirmed that the posting on the bridge can be safely increased to 14t. Observed tensile strains on the bottom faces of the concrete girders were found to be extremely small. It is suggested that the behaviour of the girders of the bridge is significantly enhanced by an internal arching action. As evidence of the arching action, two examples of thin deckslabs are presented, which are supported by girders at spacing of up to 13.5 times their thickness, and which contain no tensile reinforcement.
B. Bakht and L.G. Jaeger