| The spline function method is used to have a systematical analysis of shear-lag effect in frame-tube structure subjected to various horizontal loads. According to the hypothesis of continuum, a tube with the corner strengthened is gained to make an equal of the frame-tube. B3-spline functions and parabola functions are applied to simulate the displacement functions of the frame-tube. The system of equations about the undetermined coefficients of displacement functions is deduced by using energy-variational principle, by solving which the displacement of the frame-tube is gained. Then the internal forces in the columns and beams of the former frame-tube are obtained according to the principles of elasticity mechanics. A program (FTSF) to analyze frame-tube structure is made independently under MSVC++6.0, by using which we can get the deflection displacement of frame-tube structure under three usual types of load. To verify the B3-spline function method, a comparison of results by other methods and those from the method in this thesis is made, which has shown good agreement. It proves that the method in this thesis for frame-tube structure is reasonable and the accuracy meets the need of general engineering. In addition, the time cost of calculation is very low. Based on the former work, detail analyses of shear-lag effect in frame-tube structure as well as several factors that may influence the effect are made. The axial force and shear force of the columns, the shear force of the beams and the deflection displacement are analyzed. The effects of the load type, the stiffness of the corner columns, the ratio of length to width and the ratio of height to width on the shear-lag effect is also studied. The results show that the deflection displacement aroused by the shear-lag effect should be considered. The load type, the stiffness of the corner columns and the ratio of length to width have little effect on the shear-lag effect. But the ratio of height to width is at work. |
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