Experimental Investigation On The New-Type Outer-Plated Steel-Concrete Continuous Composite Beams And Joints

The outer-plated steel-concrete composite beam is a new type of composite beam, which evolved from the steel-concrete composite beam, and possesses favorable long-term potential by having the merits of steel-saving, good stability, large stiffness and high load-bearing capacity. The study on the outer-plated steel-concrete composite beam is therefore important in both theory and application. Based on the model test and theoretical analysis, this research investigates the load-bearing performance of both the outer-plated steel-concrete continuous composite beam and the joint connecting beam and column. The accomplished primary works and obtained achievements include:(1) The static load tests were conducted for two simply supported outer-plated steel-concrete composite beams and two outer-plated steel-concrete continuous composite beams. Test results indicate that effective cooperation can be achieved by the shear-resistant connection between the reinforcement in the negative moment area and the outer-plated steel beam. The concrete filling inside the cross section of U-shaped steel beam enhances the entire and local stability of the outer-plated steel beam. In the load-bearing limiting state, the plastic strain on sections of both the negative maximum moment and the positive one develops fully so that relatively ideal plastic hinges are formed.(2) Theoretical analyses are made and also the corresponding computation methods are proposed for the ultimate bending capacity, ultimate shearing capacity and correlation between bending and shearing of outer-plated steel-concrete composite beam, as well as the longitudinal shear-resistant performance on the interface between flange plate and web plate. The computational solutions correlate well with test results. The redistribution of internal force and the moment modulation factor of inner supports are studied for the continuous composite beam.(3) The cracking moment of concrete flange, the maximum crack width and deflection are analyzed for the outer-plated steel-concrete composite beam under the action of negative bending moment. The suggested method of calculation provides a good imitation of deformation performance for the outer-plated steel-concrete continuous composite beam in normal service state.(4) The low-cycle repeated load tests were conducted for four joints connecting the outer-plated steel-concrete composite beam and reinforced concrete column, and another four joints connecting the outer-plated steel-concrete composite beam and shaped-steel concrete column. Tests indicate that significant shear-resistant capacity and satisfying ductility and energy dissipation ability can be obtained by appropriate constructional measure so as to satisfy the engineering requirement.(5) The force mechanism of joint is investigated and the formula for calculating the shear capacity of core area of joint is presented. Some design suggestions are also given for the constructional form and measure of joint.