A Study On Shear Lag Effect Of Continuous Box Girder Under Vehicle Load

At present,few studies have been focused on the shear lag effect of multi-span continuous curved box girder,and even fewer studies have been focused on the practical calculation formula of shear lag coefficient.In the specifications,the calculation method of shear lag coefficient has not been available,while the shear lag effect inherent in curved box girder has a great influence on the safety and durability of curved box girder structure.In this work,the shear lag effect of three-span continuous curved box girder under vehicle load has been investigated,and the analysis model of three-span continuous curved box girder has been established to carry out the finite element analysis by using the general large-scale finite element software ANSYS.At the same time,the plexiglass curved box girder model with the same dimension has been fabricated to verify the reliability of the finite element analysis.Finally,the least squares method is used to implement regression analysis on the shear lag coefficient of the three-span continuous curved box girder,and the practical computational formula of shear lag coefficient is proposed.Our work is specifically summarized as follows:(1)The finite element analysis model of three-span continuous curved box girder has been established,and the distribution law of shear lag effect of seven typical cross-sections in three-span continuous curved box girder is analyzed by selecting the vehicle load and designing nine kinds of working conditions and the control sectional areas of four sections at the span center of the side span,span center of the midspan,side-bearing,inner-bearing have been determined.(2)The plexiglass curved box girder model which has the same dimension as that of numerical simulation model has been fabricated and the vehicle load test has been carried out.The experimental test has been conducted to compute coefficients of shear lag for the four control sections under nine kinds of working conditions.From the obtained distribution profiles of coefficients of shear lag,it is found that the load capacity and speed of vehicle have no obvious effect on the shear lag coefficient.By comparing with the results of the finite element analysis,the correctness and reliability of the numerical simulation method can be verified.(3)In order to further explore the influence of structural parameters on the three-span continuous curved box girder under vehicle load,15 finite element analysis models with different width-diameter ratios,height diameter ratios and depth-width ratios has been designed to obtain the distribution law of shear lag coefficient for each model section.Finally,the least squares method is used to carry out regression analysis on the shear lag coefficient to obtain the computational formula for shear lag coefficient by numerical fitting.