Analysis for effective width considered slippage of composite steel-concrete beam with lightweight aggregate

Based on energy-variational method, the interface slippage of composite beams and the variation of the effective width are analyzed. Assuming that the longitudinal displacement of composite steel-concrete beam with lightweight aggregate flange follows cubic parabola in the transverse direction, with interface relative slippage function for composite beam as unknown function, the control differential equation can be established based on minimum potential energy principle for solving theoretical distribution of longitudian stress. After solving the flange longitudinal stress, the flange effective width can be investigated. Calculating formula of the flange effective width for simple support composite beam under the continuous load, the concentrated load and the symmetrical concentrated load on two points is derived. Random sectional effective width can be analyzed with the calculation formula. As a calculating example, longitudinal variations of the effective width for composite steel-lightweight concrete beam under the different distributed loads are discussed. Considering the relative slippage influence, the flange effective width along beam length is basically constant regardless of loading conditions. Under continuous load, the flange effective width is the widest at the middle span and diminishes slightly toward the supports. Under the concentrated load, the flange effective width is the minimum at the load position and increases gradually toward two end supports.