Research On The Mechanical Behaviour And Force Transfer Mechanism Of Steel-Cement Combined Sections Of Large Span Steel-Concrete Hybrid Beams

Steel-concrete hybrid continuous girder bridges use steel box girders in the span to substantially improve the spanning capacity and navigability requirements of girder bridges,and are widely used in China’s plain cross-lake areas.The steel-mixed section connecting the steel box girders to the concrete girders is a key factor in the success or failure of the design of a steel-concrete hybrid continuous girder bridge in terms of structural construction and load bearing performance.At present,the research on the steel-mixed section is mostly at the finite element simulation stage,and there is a lack of comparative analysis of field test data.This paper takes the Hanzhuang Canal Special Bridge as the engineering background and uses finite element simulation analysis and field tests to study the mechanical behaviour and force transfer mechanism of the steel-cement combined section.The main research contents are as follows.（1）Setting and force transfer mechanism of steel-concrete hybrid continuous girder sections.By studying the structural form of different steel-cement sections of bridges and analysing the overall force performance of the sections and the force transfer ratio of each member in them,it is concluded that a reasonable range of values for the side to centre span ratio k₁is 0.4-0.5 for a full bridge of 350m,and a reasonable range of values for the centre span steel box girder length ratio k₂is 0.3-0.45.Under this range of values,the bending moment of the critical section is small and no negative bending moment occurs.（2）Steel-concrete hybrid continuous girder bridge force analysis.Midas civil was used to model the rod system of the Hanzhuang Canal Special Bridge and to analyse the load carrying capacity of the bridge during the construction and operation phases.The design of the steel-composite section was verified to be reasonable and to provide parameters for the refined modelling and analysis of the mechanical properties of the combined section girders.（3）Analysis of the stresses in the steel-hybrid combined section beam.ABAQUS was used to build a solid refinement model of the steel-cement section,and the internal force data extracted from the rod system model was loaded into the solid model for calculation,and the stresses and force transfer mechanisms of the main force transfer members of the steel-cement section under different working conditions were analysed.24.9%and 19.8%respectively.The stresses are within the safe strength range.（4）Field stress testing and verification.The stresses in each section at different stages were measured using string strain gauges and compared with the model calculation results in the finite element.This reflects the good construction control of the bridge and also verifies the reliability of the model calculation results.