高温作用后新型高强QN1803不锈钢轴压构件局部稳定性能研究

Study on Local Stability of Novel High-strength QN1803 Stainless Steel Axial Compression Members after Elevated Temperature

通过建立新型高强度QN1803不锈钢工字形和方矩形截面短柱的有限元模型对其高温作用后的局部稳定性能进行了数值模拟分析.通过参数分析探究了残余应力、局部初始几何缺陷及温度工况对构件局部稳定性能及极限承载力的影响.研究结果表明:对于方矩形构件及截面正则化长细比小于1.0的厚实工字形构件,残余应力对承载力的影响较小;对于薄柔工字形构件,残余应力会降低其截面承载力,且降低幅度随着温度的升高而下降.此外,随着温度升高,初始几何缺陷对不锈钢工字形构件承载力产生显著影响且正则化宽厚比的影响限值变大,对不锈钢方矩形构件承载力的影响则相反.最后,本文基于参数分析结果,评估了现行欧洲规范EN 1993-1-4、美国规范ASCE/SEI-8-02以及中国《不锈钢结构技术规程》(CECS 410:2015)中不锈钢构件局部稳定性能常温设计方法的适用性,发现了现有设计方法中对高强不锈钢轴心受压构件的高温作用后设计指导尚存在不合理之处并提出了优化建议.

The nonlinear finite element(FE)models of stainless steel I-section and rectangular hollow section(RHS)stub columns were established to analyze the local stability of the novel high-strength QN1803 stainless steel axial compression members after elevated temperature.Parametric analysis was carried out to analyze the effects of residual stress,initial local imperfections,and elevated temperature conditions on the local stability and bearing capacity of the members.The results show that for RHS and“non-slender”plate of I-section members with non-dimensional plate slenderness ratio less than 1.0,residual stress has little effect on bearing capacity;for“slender”I-section members,residual stress reduces the section bearing capacity,and the reduction decreases with the increasing temperature.In addition,with the increase of temperature,the limit value of non-dimensional plate slenderness ratio at which the initial local imperfections have a significant impact on the bearing capacity of stainless steel I-shaped members becomes larger,and the influence on the bearing capacity of stainless steel RHS members gradually becomes smaller.Finally,an assessment of the applicability of the design provisions for stainless steel structures at room temperature,as given in the European code EN 1993-1-4 and ASCE/SEI 8-02,together with the Chinese specification CECS 410:2015,to the design of stainless steel stub columns after elevated temperature is subsequently performed through comparisons against the obtained numerical data.It is found that the existing design codes at room temperature are not fully applicable to the design and prediction of stainless steel stub columns after elevated temperature.And there were still unreasonable aspects in the post-fire design in the existing research.It is suggested to further optimize the evaluation method of local stability of stainless steel members after elevated temperature.