Experimental Study On The Static Behavior Of Steel-concrete Composite And Laminated Beam

A steel-concrete composite and laminatied beam consists of reinforced concrete roof,steel webs with the upper and lower flange,concrete floor and connectors,where in the upper flange of the steel beam and the concrete roof with uplift restricted-slip free connectors to form a laminated interface;and the bottom flange of steel beam and concrete slab by ordinary stud connectors,form a composite interface.The uplift restricted-slip free connector is applied only to the laminated interface of the negative moment area of continuous composite beams,while the connections in positive bending area are still in the form of traditional uplift shear connectors.Based on theoretical analysis and model test of simply supported steel-concrete composite and laminatied beams,the static characteristics of the beams under negative bending moment are systematically studied.The main work accomplished includes the following:Considering the frictional resistance of the surfacing surface but unable to separate vertically,the cross-sectional bending stiffness is obtained theoretically.The basic mechanics method is applied to the theoretical analysis of the slip effect of the laminatied interface of a steel-concrete composite and laminatied beam,the slip formula and the slip strain formula under uniformly distributed load and concentrated load are derived respectively,the sliding characteristics of the laminated interface under the action of uniform load and concentrated load of a steel-concrete composite and laminatied beam in the elastic stage are analyzed by numerical examples.According to the working characteristics of the steel-concrete composite and laminatied beam,the cross-section of the negative bending moment region is obtained.The calculation formulae for the cracking moment and the elastic ultimate bending moment;taking into account the material plasticity of the steel and concrete,the calculation formula for the flexural bearing capacity of the cross section of the steel-concrete composite and laminatied beam in the negative bending moment region is obtained.Two pieces of steel-concrete composite and laminatied beams and one piece of double steel-concrete composite beam were tested in reverse static loading.The strain distributions,deflections,cracks in the concrete roof,and slippage of the converging surface with load were measured.The cracking load,yield load,ultimate load,and other characteristic values were obtained.the test results of two kinds of beams are contrasted,and the test results and the theoretical deducing part of the bearing capacity are verified each other.The experimental data and theoretical analysis show that steel-concrete composite and laminatied beam can hardly weaken the overall stiffness and ultimate bearing capacity of the composite beam in the negative moment area,meanwhile,it can significantly improve the crack resistance of the concrete slab in the negative bending area.