Response of Slab Bridges Before, During, and After Repair

Abstract

Continuous reinforced concrete slab bridges rely on reinforcing steel bars near the top of the deck over the piers to carry negative moment. Transfer of forces in these bars may be jeopardized by deterioration and repair procedures that involve variable depth removal of deteriorated concrete around the bars. Partial or full loss of continuity could overstress the bottom reinforcement. Truckload testing of three bridges with various levels of damage was conducted before, during, and after repair in an attempt to quantify the level of loss of continuity and to examine the effectiveness of repair in terms of increasing the load transfer and enhancing the overall stiffness. Test results show loss of stiffness during repair but increased stiffness after completion of repair. The continuity was found to be lost during repair, and the slab dead load positive moments may be increased by as much as 50%. After repair, the continuity was restored, and the live-load distribution was essentially unaltered. For the test bridges, the redistribution of dead-load moment to the positive-moment zones did not appreciably affect the overall bridge rating factor. The amount of moment redistribution may be controlled through planning of repair steps.