Study of In-Service Bridges Constructed with Prestressed Panel Sub-Decks (145-1)

This report describes the results of a field inspection and load test of three prestressed concrete highway bridges which have a prestressed panel subdeck. The panels, which are precast and pretensioned, span from beam-to-beam and serve as the bottom form for a cast-inplace concrete deck. The bridges examined were located in Grayson County, Texas, and were opened to traffic in August of 1963.|Crack patterns in the surface of the cast-in-place deck of two of the bridges were mapped. With only a few exceptions, the cracks found coincided with a butt joint between prestressed panels. The cracks were judged to extend approximately halfway through the cast-in-place deck. No cracks were found in the prestressed panels. Soundings to detect delamination between prestressed panel and cast-in-place deck were taken in one traffic lane of one of the bridges. No significant delamination was found. Core samples were taken from one span of one bridge, and an examination of these cores revealed no bond failure between panel and cast-in-place deck.|Electrical resistance strain gages were placed on a span of one bridge to measure transverse and longitudinal strains in the prestressed panel and cast-in-place deck. The instrumented span was subjected to both static and dynamic forces from a loaded truck. The results of these tests indicated continuity of action between prestressed beam, panel and cast-in-place deck was present.