BRIDGE SLAB CONCRETE PLACED ADJACENT TO MOVING LIVE LOADS

Traffic in lanes adjacent to a deck that is being widened or reconstructed causes deflections and vibrations in the fresh concrete deck. A study of the effects of these disturbances in concrete decks is reported here. Decks in service for years were inspected for signs of deterioration; deflections and virations were measured during concrete placement and initial curing; bridge deck cores were analyzed for cracks and signs of bonding problems in the reinforcing steel and tested for strength and pulse velocity. Laboratory beams were constructed and tested to simulate a transverse strip of a deck slab. Periodic deflections and vibrations were applied from time of casting to one day age. No deterioration that could be attributed to traffic during construction and curing of the decks was found in existing decks. The study of the cores showed no difference in cracking in cores taken from disturbed areas of the deck from that in new concrete around certain rebars dowels bent at right angles in a horizontal plane upon emerging from the old concrete. This situation was found only in cores taken at the joint between old and new concrete. The study shows that no detrimental effects in deck concrete supported by steel and prestressed concrete beams spanning up to about 100 ft should be expected when the decks are widened or reconstructed under normal traffic.