| Based on the engineering background of Jiahua rail rigid frame bridge,this paper analyzes the mechanical properties,design parameters and force transfer mechanism of steel-concrete transition section of steel-mixed structure bridge,as well as the relationship between section stress and acceleration when steel box girder is hoisted,and verifies the reliability of the results with field measured data.The main research contents are as follows:The whole bridge section was selected to establish a simplified Midas Civil model.The stress checking calculation under six load combinations was carried out,and the reliability of the results was verified by combining with the field measured data.The influence of two parameters,the span of the side span and the length of the steel box girder,on the structure stress was analyzed.The results show that with the increase of the length of the steel box girder and the span of the side span,the mid-span deflection of the main span decreases continuously,and when the length of the steel box girder and the span of the side span approach the design values of 87 m and 138 m,the negative bending moment of the unbalance on both sides of the main pier is the minimum.Under six different load combinations,the maximum stress of the mid-span section is 86.5MPa,the maximum deflection is 21.64 cm,and the compressive stress range of the concrete in the mid-span of the side span is 5.65-5.84 MPa,which is consistent with the measured data range of 5.33-6.85 MPa.A steel-concrete bonding section of 18.7m was selected to establish ABAQUS model to study the stress characteristics of steel-concrete bonding section under three different load combinations and analyze the reliability of the results by combining with the measured data.The results show that the stiffness transition of steel-concrete bonding section is smooth.For PBL connectors,the stress at the roof is greater than that at the bottom plate,and the stress at the outside is greater than that at the inside.The stress of the roof of the steel box girder changes obviously near the web,and the stress of the bottom of the steel box girder increases greatly behind the bearing plate.The error range between the simulation data and the measured data of steel-concrete bonding section is less than 20%,and the model can better simulate the actual stress state of steel-concrete bonding section.Based on the finite element theory,the element stiffness matrix of PBL connector under unidirectional load and bidirectional load is derived,and the element stiffness matrix under plastic condition is briefly analyzed,which provides some reference for the unit secondary development of finite element.A steel box girder of 87 m was selected to build ABAQUS model to simulate the stress state of the steel box girder under different hoisting conditions and analyze the relationship between the section stress of the steel box girder and the hoisting acceleration,which was compared and analyzed with the measured data.Research results show that the cross-section of floor stress and lifting point section stress and a linear relation with the hoisting acceleration,using the theory of equation and uniform state of stress were5.72 MPa and 2.23 MPa,the stress and the cross section in the roof hoisting acceleration presents three nonlinear relation,uniform stress state theory is 0.69 MPa,above all error with experimental data and the theory of stress range is within 20%;When the steel box girder is hoisted by four sling cables,the tensile stress at the lifting point of the steel box girder is relatively small.Once one sling fails,the tensile stress at the section of the lifting point will increase sharply,and the increase rate will reach more than 10 times. |
