Study On Shear Lag Effect In Prestressed Concrete Continuous Box Girder During Cantilever Construction

ABSTRACT:With the superiority of large torsional rigidity, light weight, great spanning capacity and easy construction, the thin-walled box girder has been widely used in modern bridge, but it exists shear lag effect which has impacted on the structure safety. The cantilever construction is widely used to build the most of prestressed concrete continuous box girder bridge in China, and the shear lag effect is prominent during cantilever construction. It will make the structure unsafe if the shear lag effect is ignored during construction. The shear lag effect of the beam during cantilever pouring construction which studied rare in China was tested and calculated in this paper. The main research contents are as follows:(1)Several strain sensors were placed in the top plate and bottom plate in certain cross section of prestressed concrete box girder during cantilever construction. The section stresses under the beam weight, hanging basket gravity, concrete pouring, prestressed tensioning etc. were monitored.(2)The measured stresses along the lateral distribution in the top plate and bottom plate of box girder were analyzed, and the rules of shear lag about stress were discussed.(3)The shear lag effects of the top plate and bottom plate stress of box girder during cantilever construction stage were simulated with the space finite element analysis software, and the comparasions with the experimental data were disscussed.(4) The change of the shear lag along the longitudnal direction was analyzed with the space finite element analysis software, and the wide-span ratio which affects shear lag was discussed deeply.(5)The temperature effect on the shear lag caused by the environmental temperature change was measured and analyzed.