Experimental investigation on steel-concrete composite beams with expansion joints in concrete slab

This study examines experimentally the mechanical performance of composite steel and concrete beams with expansion joints in the concrete slab. Four composite beams with expansion joints in the concrete slab were tested, and various aspects of such beams including the effects of expansion joint locations (L/4, 5L/ 12, and L/2, where L = span length), expansion joint sizes (through and half-through of the concrete depth), and loading conditions (positive bending moment and negative bending)etc., were investigated. Load versus vertical deflection responses at key sections, and the strain development and distribution on the steel beam were measured. To explore the behavior of shear connectors on or near the expansion joint sections, the normal strain on shear connectors was measured. The bending strain and axial strain of shear connectors on joint sections were also discussed in detail. The theoretical methods for predicting the rigidities and ultimate load-carrying capacities of the composite beams were examined, and it was found that the current AASHTO-LRFD criterion without considering expansion joints in a concrete slab can still provide conservative estimations of ultimate loads of such beams under a negative moment. For composite beams under a positive bending moment, however, they are not applicable, due to the different failure modes. The test results from this research provide new information for improving the design, construction, management, maintenance, and structural health assessment of such beams that can be used in bridges and buildings, etc.