Mechanical Performance of Steel-Concrete Composite Beams Subjected to a Hogging Moment

Limited experimental results have been reported in the literature on the fatigue and ultimate static loading behavior of composite beams subjected to negative bending moment. This paper examines experimentally the behavior of composite steel-concrete beams. Eight composite specimens were tested to study the various aspects of composite beams under a negative bending moment, including the effects of repeated loading, shear connectors (studs and PBLs), rubber-latex mortar coating, and steel fiber-reinforced concrete (SFRC) on their structural performance. Load versus midspan deflection, crack formation and its developing process, slip distribution on the steel-slab interface, and the flexural strain results of shear connectors were measured and studied. The test results show that the initial cracking-level repeated load did not show obvious effects, while the stabilized cracking-level repeated load can reduce the rigidity and loading capacity of composite beams. The experimental results indicate that the plastic bending moment criteria in the current AASHTO load and resistance factor design specifications are typically conservative for composite beams under a negative bending moment. In addition, the effects of SFRC on crack width control and adhesion bonding effects of rubber latex on the steel-slab interface were confirmed in the testing.