Research On The Mechanical Behavior Of Steel-concrete Composite Slim Beams In Assembled Steel Frame

Using composite slim beams in the assembled steel structure will bring good economic and social benefits. It can lower structural height, shorten the construction period and reduce the project cost. In order to realize rapid assembly of steel frame structure, this paper studied the mechanical behavior of steel-concrete composite slim beams, which can use steel as shear connector to connect the channel steel prefabricated floor slab and column reliably. The experiments focus on research of the flexural performance of 7steel-concrete composite slim beams and 1 reinforced concrete composite beam. A total of8 flexural members were tested to investigate failure process, bearing capacity, deformation performance and strain distribution in the condition of different sectional dimensions,different effective width, different reinforcement ratio and different distance of shear connector. This paper has provided the basis test materials for further theoretical analysis and engineering design proposals, which help to realize industrialized and standardized production of building components.The experiment result showed most of steel-concrete composite slim beams can accord in section assume in the elastic stress stage. With load increasing, the neutral axis moved up gradually but changed little. When the load exceeded 0.75 Pu, the tension zone of the steel beam has stepped into the stage of yield gradually, then the stiffness of composite slim beams reduced. Because of redistribution, load-deflection curve shows obviously non-linear relationship. The failure partly caused by the top of concrete flange crushed,which bring about the bearing capacity dropping rapidly, and the failure pattern is divided into flexural failure, flexural shear destruction and longitudinal shear failure. The concrete flange height、width and steel height are crucial for deciding position of the neutral axis.The lower longitudinal reinforcement, the smaller distance of shear steel plate, the sooner transverse cracks appeared, the greater crack length, and the more likely to appear the end slip phenomena. Compared with reinforced concrete composite beam, the ultimate bearing capacity of steel-concrete composite slim beams increased by 35.7% ~ 63%, and the bending stiffness increased by 8.8%~16.8%.Comprehensive three-dimensional finite element models were presented for test specimens using the ABAQUS nonlinear finite element program, the material nonlinearity and geometric nonlinearity were considered when simulation analysis. FEM results wereagree well with the experimental results. On that basis, further studies are carried out, the effects of shear connector distance on the ultimate bearing capacity are discussed. The results showed that the influence on the ultimate bearing capacity decided by the disposing space of shears, the optimal distance is 400 mm to 450 mm.The steel-concrete composite slim beams formulas of flexural rigidity in elastic stage and bearing capacity in limit state were proposed based on experimental study and simulation analysis, according to mechanics theory of materials and computing method of equivalent rectangular stress. Comparison between the proposed formulas and experimental data demonstrated that they can accurately predict the flexural rigidity and bearing capacity of compression members, which showed these methods are feasible.This paper has important significance in illustrating the mechanical behavior and failure mechanism of steel-concrete composite slim beams, revealing the quantitative relationship for the influence of distance of shear steel plate and other factors on flexural rigidity and bearing capacity of composite slim beams, improving the existing steel structure design theory, promoting the design philosophy of assembly construction, and achieving the goal of China’s steel housing industry.