Experimental study on mechanical performance of checkered steel-encased concrete composite beam

This paper presents a new type of checkered steel-encased concrete composite beam, which utilizes a convex checkered pattern in the steel beam to improve the bonding effect between steel and concrete and their cooperative performance. In theory, the checkered pattern arrangement can effectively reduce the number of bolts and enhance the slipping-resistance property of the composite beam. Thus, the new pattern improves the mechanical behavior of the composite beam. To investigate the real bending and slipping performance of the new-type composite beam, the authors conducted static load tests on six simply-supported beams. These tests enabled a thorough analysis of the experimental process of failure, load-deflection curves, strain distribution curves, load-slipping curves and slip distribution curves along the six specimen beams. The experimental results showed that given the same sectional dimensions and reinforcements, as the anti-slipping connection degree of the new-type composite beam increases, its flexural bearing capacity and ductility increase, the end slip decreases, and the failure mode of specimen changes from shear slip failure to bending failure. Based on our experiments, new theoretical formulas are given to calculate the slip and deflection of the new checkered pattern composite beams. These calculations effectively prove the bonding effect value between the checkered steel plate and concrete. The elastic and ultimate bending capacity of the composite beams were derived, considering the additional deflection caused by slip effect. It has been shown that theoretical values of the deflection and bending capacity calculated by the formulas are in agreement with experimental values.