THE Ultimate Strength Analysis Method of Thin-Walled Beam Structures by Using of Rigid Body-Spring System Models

建立了适用于薄壁梁的S离散模型。通过建立描述弯扭现象的运动场，对由刚性梁单元和弹簧系统组成的模型进行了分析所需的公式，并对薄壁刚性单元-弹簧系统进行了数值分析，以考察该方法的有效性和实用性。(1)薄壁梁在弯曲和扭转作用下的弹性空间行为。(2)薄壁梁在弯曲和轴力共同作用下的弯扭屈曲问题。(3)薄壁梁在弯曲和扭转作用下的极限性能。(4)薄壁梁在弯曲作用下的弹塑性侧向屈曲。(5)大变形问题，如梁柱的后屈曲行为，数值处理结果令人满意。应用这种离散化的分析方法，可以处理薄壁构件的弹塑性屈曲和后屈曲行为，以及薄壁结构的极限强度分析。

S discrete model which is useful for the thin-walled beam, is developed. By setting up the appropriate kinematic field which accounts for flexural-torsional phenomenon, the formulation required for the analysis is carried out for the model which consist of rigid beam element and spring systems.The following cases are analyzed numrically using the proposed model, that is thin-walled rigid element-spring systems, for the purpose of investigating the validity and the practicability of this method. (1) Elastic spatial behavior of thin-walled beams under bending and torsion. (2) Elastic flexural-torsional buckling of thin-walled beams under bending and axial force. (3) Ultimate behavior of thin-walled beam under bending and torsion. (4) Elasto-plastic lateral buckling of thin-walled beam under bending. (5) Large distortion problem such as post buckling behavior of beam-column.The numerical treatments are found to be satisfactory. By applying the method of analysis involving discretization, such as the one described, it is possible to treat problem such as inelastic buckling and post buckling behavior of the thin-walled members, as well as the ultimate strength analysis of thin- walled structures.