Clarification of the occurrence mechanism of out-of-plane deformation of steel beam-columns subjected to cyclic bending and theoretical prediction of the critical states

本文通过理论分析和试验研究，阐明了钢压弯构件平面外变形的发生机理，并建立了平面内极限承载力的预测方法.针对由刚性框架和具有线性应变硬化特性的弹塑性弹簧组成的四自由度悬臂空间梁柱模型，证明了面内行为极限的存在，并探讨了面外行为极限的发生机理。平面变形已得到澄清，在一个封闭形式的分析解决方案的整个滞回响应的模型，以循环弯曲程序，逐步增加振幅。建立了一种无需跟踪整个滞回响应就可以预测平面内行为极限的理论.本文将平面内性能极限理论推广到一维连续四翼缘梁柱模型，分析了四翼缘梁柱的平面内性能极限。 ...更多信息 得到了面内行为极限的理论解.建立了空间梁柱的平面内性能极限理论，并将其应用于更符合实际的空间梁柱模型。这一理论为制定改进的钢梁和柱设计公式提供了基础数据。(1)A本文提出了一种考虑截面翘曲变形的任意形状实心截面空间钢梁柱弹塑性大挠度分析的新的有限元模型。（2）建立了该模型的面内行为极限理论。对于服从Prager和Zieglar随动硬化定律的材料，导出了除交变塑性状态外的所有变化模式下，与稳态增量变化有关的应力速率和应变速率之间的关系。(3)A编制了基于该极限理论的数值分析程序.本文对方钢管和H形截面钢梁柱试件进行了逐步增幅的全周反复弯曲试验。试验结果证明了面内行为极限和稳态极限的存在，并证实了理论研究的几个主要发现。少

Theoretical and experimental investigations have been carried out in order to clarify the occurrence mechanism of out-of-plane deformation in steel beam-columns subjected to reversed cyclic bending and to establish a prediction method of the in-plane behavior limits.1. For a 4 degree-of-freedom model of cantilever space beam-column, which consists of a rigid frame and elastic-plastic springs with linear strain-hardening characteristics, the existence of in-plane behavior limits has been proved and the occurrence mechanism of out-of-plane deformation has been clarified by obtaining the analytical solution in a closed form of the entire hysteretic response of the model to a cyclic bending program with gradually increasing amplitude. A theory, which can predict in-plane behavior limits without tracing the entire hysteretic response, has been established.2. The in-plane behavior limit theory has been extended to a one-dimensional continuum beam- column model with four flanges and the analy … More tical solutions to the in-plane behavior limits have been obtained.3. The in-plane behavior limit theory has been developed for a more realistic model of space beam-column. This theory is expected to provide the basic data used in constituting improved design formulas for steel beams and columns. (1)A new FEM model has been proposed, which permits large deflection analysis of elastic-plastic behavior of a steel space beam-column with an arbitrary shaped solid cross-section taking into account warping deformation of cross-sectional planes. (2)The in-plane behavior limit theory has been constructed for this model. The relations between stress rates and strain rates associated with the increment variation of steady state have been derived for all patterns of variation except those from the states of alternating plasticity for the materials subject to Prager's and Zieglar's kinematic hardening,laws. (3)A computer program for the numerical analysis based upon this limit theory has been made.4. Completely reversed cyclic bending tests with step-wisely increasing amplitude have been carried out for steel beam-column specimens with square tubular and H-shaped cross- sections. The test results have demonstrated the existence of in-plane behavior limits and steady state limits and confirmed several major findings from the theoretical studies. Less