Space Deformation Analysis Of Thin-walled Structure

Thin-walled elements greatly externalize the light-weight and high-strength character of the steel structure, and as the light steel structures are built more and more, the problem of the use of thin-walled elements is becoming more and more serious. This paper firstly introduces "warping theory" presented in literature cite[1], then use it to solve a lot of examples. It's pointed out that "warping theory"is not only all correct and advanced in the field of theory but also useful and effective in engineering practice. This paper mainly finished these following jobs:(1)General introduction of "warping theory", It represents the basic hypotheses and calculation model, considering thin-walled element as member structure composed of a lot of narrow rectangle section elements which linked at spine, and it regards the thin-walled element as a kind of hypostatic structure. "Warping theory" presents two conception: moment vector and angle radius vector, and with them the uniform equation used to calculate inner force and deformation is deduced. At the same time, it creates a new method: dynamic coordinate method. "Warping theory" unifies "plane bending theory" and "constraint twist theory", it also transplants the methods of "plane bending theory" to "warping theory", and this brings great goodness in calculation of stress and deformation, especially to the beam with complexes or the variable section beam. It also clarifies the action of free torsional stiffness and points out that free torsional stiffness should be put at second analysis.(2) Based on the space deformation calculation of thin-walled elements, when the free torsional stiffness is ignored, a simple hypostatic beam is solved by force method and displacement method to explain the use of "warping theory".(3) Space deformation analysis of thin-walled pallet. The effective hypothesis of plane frame is transplanted to thin-walled pallet, and a new calculation model is presented, which points out that when the loads is perpendicular to the plane which is composed of lines joined by shear center, the thin-walled board-frame can be calculated according to across-beam-series; and when the loads is parallel to that plane, according to the conception of "single-layer frame", it can be calculated on the base of plane frame. By this way, it is not trouble by coupling blank tear, at the same time, calculation is greatly simplified and the deformation is very clear to us.(4) The variable section beam is solved with matrix displacement method. It breaksthrough the traditional restricts, and with the method of directly calculating the space deformation of thin-walled elements, it deduce the element flexible matrix at first, then associating conditions of balance and deformation compatible the space deformation of the thin-walled beam is given. It also deduces element stiffness matrix of thin-walled structure, and use matrix displacement method solving the same beam. The results suggest that these two method are both correct. And it tells us that in the calculation of thin-walled structure, displacement is better then force method, because the data in the element stiffness matrix is more simplify.Of course, the work need pushed on. For example, how to use matrix displacement in calculation of multi-layer thin-walled space frame, how to use dynamic method in the nonlinear field and the field of dynamic analysis, and how to consider the sectional aberration, and so on, all these problems need much labour.