Experimental Testing and Behavior Of TxDOT "Poor-Boy" Link Slab Details for Multi-Span Bridge Decks

Abstract

This research investigated the behavior and performance of link slabs in bridge decks, focusing on details for Texas Department of Transportation (TxDOT) standard bridges and modifications to those details. Several bridge specimens featuring link slabs were constructed and subjected to load to induce negative bending across the link slab. Two of these specimens followed existing TxDOT "poor-boy" joint details, one using flush panels and the other using offset panels. Two other specimens focused on retrofitting existing details, while the last specimen featured debonding from the girders and the addition of top reinforcement for crack control. These specimens were constructed and tested at the Center for Infrastructure renewal at Texas A&M University. It was found that the continuity provided by the link slab did not significantly impact girder end rotations, as observed through the near-linear load vs. rotation response for each specimen, confirming previous literature. The strain distribution in the link slab varies depending on detailing, distance from the center of the link slab, and reinforcement distribution. Strains are generally concentrated at the center of the link slab, but debonding can result in these strains being distributed over a larger portion of the deck. Crack widths were also observed and were found to be influenced by crack location, overall detailing, and reinforcement distribution in the deck. The number of cracks varied with deck detail, with debonding resulting in distributed cracking rather than concentrated cracking. Based on these findings, several modifications are recommended for future TxDOT "poor-boy" joints. These include adding additional top reinforcing, incorporating a debonded layer, and re-evaluating the flush panel detail for the presence of the wooden board. Future work should be performed to consider the effect of bridge geometry and skew as well as the effects of temperature gradient and the effects of putting the link slab into positive bending.