Test Researching On Shear Lag Effect In Continuous T Beam

Due to its good mechanical properties,box beam and T-beam has been widely used in bridge engineering.Box beam and T-beam is characterized by reasonable in structure,economical in cost,strong in anti-bending and anti-twisting,however,the shear lag effect is extremely prominent.In the 1970 s,numerous box girder bridges were damaged due to the stress concentration which is caused by the ignorance of shear lag effect in design.After that,shear lag effect is gradually brought to the forefront by international scholars.In previous studies,the unknown displacement function is assumed to solve the shear lag problem in box girder while the bending moment and shear force on the effect of shear lag and strain distribution along plate thickness direction are usually ignored.For the shear lat problem of multi-span continuous T beam varies along the flap transverse direction in the stress state,this report has done the following work:Firstly,the self-produced experimental model is introduced in this paper.Moreover,the material property experiment and the arrangement of measuring points on the cross section are also introduced.In order to research the problem of continuous T beam during the loading process comprehensively,we arrange the strain sheets in the surface of concrete,fixture in the flank-web and belly-web and internal concrete.So,we get a large amount of data in the experiment,which it provides data support for analysis of shear lag later.In order to research the strain distribution problem under the different stress state,we arrange totally six sections which are provided with typical force characteristic.They are respectively: The distance from A-A section to edge-seat is about 100 mm.The bending moment is small and it mainly bears shear force.B-B section is 750 mm away from edge-seat.It bears the joint effect of shear and bending moment.C-C section and D-D section are located in symmetrical position of the loading point.They have different bending moment and same shear which have theopposite direction.E-E section only bears the shear force and this location has no bending moment.F-F section is 100 mm from the middle bearing,by the combined effect of negative moment and shear.Then this report introduces the experimental research concrete wide-flange continuous T beam concentrated force loaded,and analyzes T beam typical sectional strain distribution along the transverse and thickness rules,shear lag coefficients along horizontal and vertical rules,and also study the effect of shear force and bending moment on shear lag.The research results show that the shear lag effect of T beam in the middle bearing is obvious.The phenomenon of shear lag is not apparent in the section of pure shear and edge-seat.In general,the shear lag in internal surface of slab is more obvious than in external surface.With the bending moment increasing,the shear lag effect of typical sections is more significant.