巨型截面短深钢梁力学性能

Shear deformation is negligible for huge-section steel beam with smaller span-height ratio. However, the current analysis theory and design code for steel structure can not represent the real mechanical behavior of steel beam with bigger sectional dimensions and smaller span-height ratio. In this proposal, a first-order beam theory is developed which includes the effects of shear deformation due to bending and torsion. Displacement mode of new beam element is obtained through the solution of differential equation of the first-order beam theory, which avoids the shear locking. And then the new spatial beam element model is developed, which includes the effect of shear deformation caused by coupling of bending and torsion as well as P-δ effect. Gradual yielding along the section and length of steel beam is modeled through infinitesimal area on cross-sections. The corresponding finite element analysis program is developed, which can be used for the short-deep steel beam. Experimental studies and finite element analysis are carried out to explore the mechanical property of huge-section and short-deep steel beam. Through the studies in this project, it is expected that, in theory, the effect of shear deformation on the flexure and torsion behavior of huge-section short-deep steel beam is revealed, the definition of huge-section and short-deep steel beam is specified, and also, the spatial beam element for short-deep steel beam is built up, the rules of stress distribution and deflection are illustrated. In practice, analysis procedure is provided for the analysis of steel structure and relevant theoretical evidences are provided for the design of huge-section short-deep steel beam

巨型截面钢梁截面尺寸大，跨高比一般较小，剪切变形影响不能忽略，当前钢结构分析理论与规范并不能真实地反映巨型截面短深钢梁实际受力性能。本项目拟建立同时考虑弯曲和扭转剪切变形的一阶梁理论。以一阶梁理论微分方程的解为基础得到新型梁单元的位移模式，推导适用于短深钢梁，综合考虑弯曲和扭转剪切变形、弯扭耦合以及P-δ效应等影响因素，可跟踪塑性发展的新型空间梁单元模型。在此基础上编制相应的有限元分析程序。同时，对巨型截面工字钢梁进行试验研究与有限元分析，研究各参数对短深钢梁的静力力学性能的影响。通过本项目研究，希望能在理论上揭示剪切变形对短深钢梁弯扭性能的影响，明确巨型截面短深钢梁的尺寸界定，建立适用于短深钢梁的梁单元模型，阐明钢梁各参数对其应力分布和挠度变形影响的规律；在应用上，可为短深钢梁及其钢框架提供分析工具，并对以后巨型截面短深构件的设计提供理论依据。

为了考虑剪切变形对薄壁钢梁力学性能的影响，在Vlasov薄壁梁理论的基础上发展了考虑剪切变形影响的一阶薄壁梁理论。由于截面剪心的特性，薄壁钢梁的弯曲与扭转是解耦的，可以单独推导相应理论。于是，分别对薄壁构件的弯曲和扭转问题进行了分析研究，建立了相应的微分方程。在新型薄壁梁单元推导的基础上，利用面向对象的C++语言编制了非线性分析程序，并利用数值算例进行了验证。算例分析表明，建立的有限单元模型可以给出更精确的结果，并且避免了剪切自锁现象的发生。.对巨型截面短深钢梁进行试验研究，试验对象包括8根构件，其中4根为普通工字钢梁构件，2根为均质叠合梁，2根为混合钢种叠合梁，构件的跨高比均在3~6之间。在叠合梁试验结果基础上，总结了叠合梁与普通工字型钢梁的主要力学性能差异，证实了混合钢种叠合梁的设计经济性，并提出了具体的设计建议。通过静力荷载试验和相应的有限元分析，证实了短深钢梁整体稳定和局部稳定问题的相关性。为研究设计参数对钢梁力学性能的影响规律，引入了分类设计的概念，并基于有限元数值分析的结果，分别提出了工字型截面构件在弯剪作用下的截面分类及构件分类方法，为构件设计方法的发展提供参考。.通过试验和有限元分析，已证实局部稳定对构件整体的力学性能存在显著影响。尤其对于跨高比较小的工字型短深钢梁，由剪力主导的破坏模式有腹板局部失稳的显著特点。然而，一阶梁理论中包含了刚周边假定，即无法考虑板件的局部屈曲作用。为进一步建立合理的短深钢梁力学模型，引入了非线性广义梁理论模型，并利用FORTRAN编制了相应程序，进行算例分析和讨论。算例分析表明，广义梁理论模型能准确模拟构件的力学性能，不但包含了板件局部屈曲变形和中面剪切变形，亦可对各类变形的影响程度进行量化。