| The double is used frequently in concrete cable-stayed bridge with double cable plane.The bridge panels is so thin and wide that shear lag effect should put more attention on.By talking Xiantao Hangjiang bridge as the project background,to study the shear lag effect in cable-stayed bridge with double main ribbed,some factors of the shear lag analyses basing on finite element were carried out during the finished bridge state,such as the transverse slope、thickness of section roof and cross diaphragm.This dissertation includes four parts as following.(1)The development of the study on shear lag at domestic and overseas is mentioned in three aspects,including calculation theory、influence factors and effects on bridge.(2)With the energy variation method,shear calculating formula of lag effect can be further explored.According to the finite element principle,the software Midas Civil establish is used to establish the full-bridge model,at the same time,the solid model of full-bridge is established by using the finite element software Midas Fea.And the factors of changing shear lag effect,including the transverse slope、thickness of section roof and cross diaphragm were analyzed by establishing different finite element model.(3)Transverse slope makes change of longitudinal normal stress near the middle area of the deck,when the section is only under self-supporting effect obviously.By changing the section parameters,transverse slope affect the shear lag effect,the section parameters refer to transverse slope.With all factors considered,2.0%transverse slope is the best choice.(4)The thickness change of section roof has influence on section parameters,as a result,it has influence on shear lag effect.When the section parameters is minimum,the thickness of section roof is 30cm.With all factors considered,30cm is the best choice,which means the reference value of minimum section parameters.(5)Cross diaphragm can improve the stress distribution obviously by decreasing the longitudinal normal stress near the middle area of the deck and increasing the longitudinal normal stress near the ribs,which makes the longitudinal normal stress in homogeneous distribution.As a result,The significant effect of cross diaphragm should be considered when calculate the shear lag effect. |
