The Shear Stress Transfer In The Junction Of T-beam And The Stress Distribution In The T-beam

The problems of shear lag have been studied since 1920 s.Though several ten years developed, some achievements has been made in the research of shear lag. Despite these achievements can sole some pratical engineering problems, there are still many unresolved promblems needed to be a further research about the effect of shear lag.Previous studies mostly focus on the research of thin-walled box girder, but little study has been done for the shear lag of T-beams with wide flanges, and less study of shear lag has been done when the flanges of T-beams change. In the aspect of the experiment studies, the component has deadweight when the member is placed horizontally. But the studies of shear lag did not consider the role of dead load, this would cause the inaccuracy and uncertainty of studies on the mechanism of the shear lag effect.In this dissertation, the above two issues are studied by test-researching and analyzing. The conclusions and outlook are obtained at last. The main contents are the followings.(1) In order to eliminate the impact of the component weitght on shear lag, a test device is designed that can make cantilever T-beam model become a vertilcal structure, and horizontal loads can be loaded.(2) Plexiglass T-beam models are made with different flange width, divided into four sections in the longitudinal which are A section,B section, C section and D section from bottom to top. Strain-gauges are stuck onto flange plate surface and the surface of the web around in each section at the same time. And also strain gages are pasted in the junction of the web and flange plates. So the bending strain can be measured along the width direction.(3) Four loading schemes are introduced, which include the free end load, pure bending load, the anti-bending load and mid-span load. In the free end loading, with the bending moment and shear force increase, the shear lag effect more obvious; In pure bending secions, the flange plate shear lag effect is basically the same on A andB sections; At the curved section, acting only by shear stress, the strain is basically zaro on the sureface of flange pate up and down. In the case of mid-span loading, C section appear negative shear lag effect on the flange plate.(4) With the strain of junction researched in the four loading model, it is known: in the case of the free end loading, along the longitudinal direction, from the fixed end to the free end, the strain increases; As the load increasing, the junction strains are increasing gradually in A and B sections; In the case of pure bending load, the junction strains are the same in A and B sections; In the case of the anti-bending load, with load increasing, the value of junction strain in A section increases, but the junction strain of B section essentially zero; Under the mid-span loading, along the longitudinal direction, from the fixed end to the free end, the junction strain decreses, and the strain of C section is negative.(5) Though the comparion of the shear lag coeffient and strain cure in different width of the T-beam flange, it is known: Under the free end loading, the shear lag coefficient of A section is increasing with the increase of flange width, and shear lag effect is more and more obvious; In the case of pure bending load, the degree of shear lag effect does not change with the vary of wing plat width.