| Steel-concrete composite beams can give full play to the advantages of steel beams and concrete materials,and have the characteristics of high bearing capacity and convenient construction,which has been widely used in the industry.However,with the development of China’s construction industry,the industrialization of building structure has become the trend of future construction industry development.The shortcomings of existing steel-concrete composite beams,such as low assembly rate and large wet operation on site,gradually appear.Therefore,in order to solve the above problems,a steel-variable-step precast composite slab structure with higher assembly rate is proposed.Based on the original composite slab,a new type of peripheral composite precast floor slab is used in the steel-variable precast composite slab composite beam,which makes the assembly rate of the floor slab system in the composite beam increase to over 70%.In order to further shorten the connection width of the post-cast strip,improve the assembly rate,a connection method using ultra-high performance concrete UHPC as the material of the post-cast strip is put forward,and the bending performance of the steel-pre-cast composite beam with the connection method is studied.The main research work and achievements of this paper are as follows:(1)The experimental research on the flexural behavior of steel-variable-step precast composite slab composite beams is carried outSix steel-stepped precast composite slabs connected with ordinary concrete,one steel-stepped precast composite slabs connected with UHPC and one steel-ordinary concrete composite slab were designed.Through three-point loading test on eight composite beams,the bending performance of steel-stepped precast composite slabs under different design parameters was compared and analyzed.The test results show that the failure rules of all composite beams are basically the same,and the ultimate failure modes are bending failure.The ultimate flexural capacity of steel-stepped precast composite slab composite beams connected with ordinary concrete is similar to that of steel-ordinary concrete composite beams,while the ultimate flexural capacity of steel-stepped precast composite slab composite beams connected with UHPC is higher than that of other two types of composite beams.(2)Finite element parametric analysis of bending performance of steel-variable-step precast composite slab composite beams is carried outOn the basis of the test,the finite element foundation model of effective steel-ordinary concrete composite beam specimen SCB8,steel-variable precast composite slab composite beam specimen SCB1 under ordinary concrete connection and steel-variable precast composite slab composite beam specimen SCB7 under UHPC connection is established by using ABAQUS software.Based on the finite element model,parametric analysis is carried out.The results of the finite element model show that the strength of steel beam is one of the main parameters that affect the ultimate flexural capacity of steel-stepped precast composite slab composite beams,while the strength of ordinary concrete in post-cast strip,transverse reinforcement ratio and the laying length of stepped precast composite slab have little influence on the flexural capacity of composite beams.At the same time,it is found that the steel-fully precast floor composite beam connected by UHPC also has good bending bearing capacity.(3)This paper discusses the calculation method of bending bearing capacity of steel-variable-step precast composite slab composite beamsBased on the existing formulas for calculating the flexural capacity of steel-concrete composite beams,this paper discusses the calculation method of the flexural capacity of steel-variable precast composite slab composite beams.Through theoretical calculation and analysis,it is found that the elastic bending bearing capacity of steel-stepped precast composite slab composite beams can be calculated by the converted section method,the ultimate bending bearing capacity can be calculated by the simplified plastic analysis theory,and the deflection deformation in the elastic stage can be calculated by the reduced stiffness method. |
