Stiffness and cracking of web-embedded U-shaped steel-concrete composite beam under negative bending moments

This paper discusses the deformation behavior of web-embedded U-shaped steel and concrete composite beams (WUSCB) under negative bending moments. A negative bending moment test was carried out on eight WUSCB specimens. The mid-span vertical deflection, relative slip between slab concrete and U-shaped steel, and main crack width of concrete slab were measured. The specimens have stable initial stiffness and secondary stiffness, and exhibited the final bending failure mode. Meanwhile, the WUSCB express good integrity and deformation ability, which is attributed to the good shear connection performance of the web-embedded shear connectors. Based on the test, the calculation methods of initial stiffness, secondary stiffness and main crack width of concrete slab are proposed, which are in good agreement with the experimental results.