| The steel-concrete composite beam has the advantages of high bearing capacity,good seismic performance,convenient construction,short construction period,material saving and convenient installation of pipelines.However,in the process of using,the continuous steel-concrete composite beam will produce the adverse situation of concrete tension and steel beam compression in the negative moment area,which will cause the concrete cracking,resulting in the decrease of the rigidity and durability of the composite beam.In the design of steel-concrete composite girder bridge,how to prevent the concrete slab cracking in the negative moment area has become a key problem.At present,a kind of uplift restricted-slip free connectors has been used in the steel-concrete composite continuous beam bridge.It can increase the prestress application efficiency of the concrete deck in the negative moment area by releasing the longitudinal constraint between the concrete slab and the steel box girder.Based on the engineering background of Xiaoqinghe No.1 Main Bridge in the high and wide section of Changshen expressway,this paper studies the mechanism of the influence of the uplift restricted-slip free connectors on the structural stiffness,deformation and stress,as well as the degree of its influence on the bearing capacity.The main work and research results are as follows:(1)In this paper,the finite element model of steel-concrete composite continuous beam is established,and the correctness of the finite element model is proved by the real bridge monitoring data.On this basis,the finite element model is improved.Based on the original model,the connection form is modified,and the finite element model of steel-concrete composite continuous beam bridge with traditional stud is established.Based on the above two models,the paper compares the relationship between the types of shear connectors and the basic mechanical characteristics of the structure,in order to further clarify the influence of the types of connectors on the mechanical characteristics of the structure.(2)In order to reflect the relationship between the change of shear stiffness and the mechanical properties of the whole structure,the paper sets up the continuous change of shear stiffness to reflect the influence of the change process on the mechanical properties of the bridge.The results of finite element analysis show that the uplift restricted-slip free connectors can effectively improve the effect of prestressing and the compressive stress reserve of concrete in the negative bending moment area,but it will also weaken the overall stiffness and bearing capacity of the structure,increase the vertical deformation of the structure and generate greater relative sliding of the interface in the negative bending moment area.At the same time,the research of shear stiffness shows that the shear stiffness of the connection in the negative moment area has a great influence on the stress,deformation and relative slip of the structure when the shear stiffness of the traditional stud is 0 ～ 20%.(3)In order to reflect the influence of the uplift restricted-slip free connectors on the basic mechanical characteristics of continuous beams,the paper selects the parameters of the bridge deck concrete strength,the bridge main span,the longitudinal arrangement density of connectors,the transverse arrangement density of connectors,the arrangement range of the uplift restricted-slip free connectors,and the web height for sensitivity analysis.The results show that,for the composite beams with uplift restricted-slip free connectors,changing the ratio of the moment of inertia between the concrete part and the steel box part in the composite beam section,changing the density of the connectors in the negative moment area have no effect on the stress distribution in the negative moment area;the main beam span and the layout range of the uplift restricted-slip free connectors are the main factors affecting the effect of the connectors. |
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