Experimental Testing and Behavior of TxDOT "Poor Boy Joint" Link Slab Detail Using Flush Panels

Abstract

Expansion joints are commonly used in bridge decks to provide relief from thermally induced stresses. While beneficial in this regard, the presence of these joints presents opportunities for damage to form in the bridge deck and substructure if proper maintenance is not performed. Continuous bridge decks, or link slabs, have been used to reduce the number of expansion joints and have had promising results. Previous studies in literature have focused on debonded link slabs. A full-scale experimental test has not been presented in literature for a fully bonded link slab let alone for the “Poor Boy Joint” link slab detail used by TxDOT.

This thesis involves the development of an experimental test setup capable of loading the “Poor Boy Joint” and assessing its performance. In service, this detail is susceptible to forming a single transverse crack that may result in undesirable wear in the deck, corrosion of deck reinforcement, and damage to the substructure due to water infiltration. In some cases, secondary cracks offset from the primary crack have been observed. A two-span, two-girder line experimental test setup was designed, instrumented, and tested under symmetric and asymmetric loading to simulate service demands caused by thermal and live loads.

The loaded specimen experienced damage comparable to that observed in bridges currently in service, providing insight into the underlying conditions for crack formation. This damage included transverse primary and secondary cracks, transverse bottle-neck cracks, and diagonal torsion cracks.

Along the primary crack, crack measurements were taken in 13 locations. The widest cracks formed in the deck between the two girder lines. The next largest cracks formed in the deck between the girders while the cracks in the overhang were the smallest. The measurements were plotted with respect to the average total rotation of the girder lines.