Study On Mechanical Properties Of Steel-concrete Composite Beams Based On Multi-scale Finite Element Method

In recent years,with the large-scale construction of transportation infrastructure in China,the steel-concrete hybrid bridge,which combines the advantages of steel structure bridge and concrete structure bridge,is rising day by day.As one of the main structural forms of the steel-concrete joint section,the front and rear pressure plate type has complex structural forms and significant difference in material properties.The mechanical behavior of the steel and concrete joint section is still not clear to design researchers.Different construction methods have a great impact on the final force of the steel-concrete joint section.In this paper,the multi-scale modeling method can be used to simulate the construction of the steel-concrete joint section,and the research results can provide guidance for the modeling method.Parameter analysis and structural replacement of the steel-concrete joint section are carried out,and the research results can be used as guidance for the design of the steel-concrete joint section.The main research contents of this paper are as follows:1.Four models,namely beam element model,fine full bridge model,fine local model and multi-scale model,were established simultaneously.The precision full-bridge model is used as the verification group,the multi-scale model is used as the experimental group,and the beam element model is used as the comparison group.The calculation results of the three models illustrate the correctness and advantages of the multi-scale modeling method.With the refined full-bridge model as the verification group,the multiscale model as the experimental group,and the refined local model as the contrast group,the stress and displacement results of the three models are used to illustrate the disadvantages of the local and refined models and the advantages of the multi-scale model.2.Taking the concrete section of Zhongwei Yellow River Bridge(special-shaped arch bridge)and the common T-beam section as the research object,the concept of effective length of local fine model is proposed,and the finite length value of these two sections is calculated.3.The multi-scale finite element model of the full bridge is established and its correctness is verified.At the micro level,stress and stress gradient are used as indexes to compare and analyze the stress of each member of the steel-concrete joint section under different construction procedures.At the macro level,the ratio of internal forces between steel structure and concrete structure in steel-concrete joint section under different working procedures is compared,and different indexes are proposed to evaluate it.The section is taken as the whole to partition,and the working efficiency of different parts in the whole section is analyzed.4.According to the proposed axial force transfer index of the steel-concrete joint section,the influences of parameters such as the length of the steel-concrete joint section before and after the pressure plate,the thickness of the rear pressure plate and the height of the steel lattice cell on the internal force transfer performance are further analyzed.5.Under the multi-scale modeling method,the original single concrete lattice structure is replaced by double concrete lattice structure,and the influence of different structures on the axial force transfer and bending moment transfer is discussed.