| Composite girder Bridges with corrugated steel webs have been widely used in bridge construction because of their advantages such as high prestressing rate,reasonable distribution of shear moment and high shear strength.However,initial defects(including initial geometrical defects and welding residual stresses)will inevitably occur in the process of manufacturing,transportation and hoisting of corrugated steel web beams,which will inevitably have certain adverse effects on deformation,stability and fatigue resistance of corrugated steel web beams.Therefore,this paper studies the influence of initial defects on the buckling performance of corrugated steel web structures by combining experiment and numerical simulation.The specific research contents and results are as follows:(1)The welding residual stress test of the corrugated steel web beam was carried out,and the general temperature distribution of the structure in the welding process and the whole process of welding strain changes were determined.The results showed that:the five test sections formed a significant temperature gradient on the temperature line at the same position from the weld,and the temperature variation trend was basically the same on the same temperature gradient line;The strain variation trend at each measuring point of steel web and bottom plate is the same.Different from steel web,the strain variation at each measuring point of bottom plate presents a zigzag pattern of alternating tension and compression during the heat source phase.(2)The causes of initial geometrical defects of corrugated steel web beams are summarized and analyzed.By comparing the limit requirements for the initial geometrical defects of steel members in various countries,and summarizing the research status of the initial geometrical defects of corrugated steel webs beams by domestic and foreign scholars,it is found that the initial geometrical defects of corrugated steel webs beams present a sinusoidal distribution.In the subsequent nonlinear buckling analysis of corrugated steel web beams,the local defects and welding residual deformation of corrugated steel web beams are taken as equivalent geometric defects by referring to the European specification EN1993-1-5,and the amplitude of the initial geometric defects is uniformly taken as 1/200 of the height of the web,which is more safe.(3)The thermodynamic finite element calculation theory of welding was summarized,the finite element model of welded member with corrugated steel web beam was established,and the distribution of the lateral and longitudinal residual stresses of the welds along the weld,perpendicular to the length of the bottom plate and parallel to the height of the web was analyzed,and the calculated results were compared and verified with the test data.Based on the results of thermal-mechanical coupling analysis,the parameters of the existing welding residual stress model of corrugated steel webs were adjusted and simplified to make it more convenient to apply to the finite element model,so as to carry out the mechanical analysis considering the welding residual stress.(4)A finite element model which can simulate the initial geometrical defects and residual stresses and accurately analyze the shear buckling performance of welded corrugated steel webs was established.The initial stiffness,ultimate buckling capacity and ultimate post-buckling capacity of the components were investigated,and the reliability of the finite element model was verified by the relevant test results of other scholars.The verified finite element model was used to analyze the shear buckling properties of corrugated steel webs.The effects of the type of corrugated steel webs,the thickness of the webs t_w,the height of the webs h_wand the height of the webs h_ron the shear properties of corrugated steel webs were studied under different steel strength levels.(5)By changing the thickness of corrugated steel webs t_w,the height of corrugated steel webs h_wand the depth of corrugated steel webs h_rof three different types of corrugated steel webs beams,144 finite element examples are generated in total.According to the distribution characteristics ofρ-λ_scurve,the formula for calculating the lower limit of shear strength of high strength steel with corrugated steel webs is obtained by multiple linear regression fitting.The results show that the mean value and coefficient of variation of the ratio between the fitting formula and the finite element result are 1.18 and 0.018,respectively.The fitting formula can be used to calculate the lower limit of shear strength of corrugated steel webs. |
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