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连续组合梁的极限承载力由侧向畸变屈曲、局部屈曲,或者由两者的相互作用决定,这一点与纯钢梁的扭转屈曲破坏模式完全不同。利用有限元模型对负弯矩区的组合梁进行了弹塑性有限元分析,其中考虑了初始几何缺陷和残余应力,最终发现有限元分析结果与试验结果吻合良好。另外,对负弯矩区的预装体外钢筋的组合梁进行了参数研究。分析了影响组合梁承载能力和屈曲弯矩抗力的因子,如初始几何缺陷、钢梁的残余应力、力比值、预应力范围、负力矩钢筋、板、翼缘和梁的宽厚比。利用有限元法对负弯矩作用下的25组共200根具有不同截面参数、初始几何缺陷、残余应力和不同力比值的组合梁进行了分析。将计算出的屈曲弯矩率与改进宽厚比的曲线与中国规范中钢柱设计曲线进行了对比。结果证实:对于改进了的宽厚比值,本文依据中国规范的设计曲线推导出来的设计方法可以用于对组合梁屈曲强度的评估。
The ultimate bearing capacity of continuous composite beams is determined by the lateral buckling, local buckling, or the interaction between the two. This is totally different from the torsional buckling failure mode of pure steel beams. The finite element model was used to analyze the elasto-plastic finite element analysis of the composite beam with negative moment area, in which the initial geometric defects and residual stresses were considered. Finally, the results of finite element analysis were in good agreement with the experimental results. In addition, the parameters of the composite beams with pre-installed external reinforcement in the negative moment area were studied. The factors that affect the bearing capacity and flexural moment resistance of composite beams are analyzed, such as initial geometric imperfections, residual stress and force ratio of steel beams, prestressing range, aspect ratio of negative moment bars, plates, flanges and beams. A total of 200 composite beams with different cross-section parameters, initial geometric imperfections, residual stresses and different ratios of forces under negative bending moment were analyzed by finite element method. The curves of buckling moment rate and improvement of width-to-thickness ratio were compared with those of steel bars in China code. The results show that the design method deduced from the Chinese design curve can be used to evaluate the buckling strength of composite beams.