Equivalent bow imperfections for use in design by second order inelastic analysis
Equivalent bow imperfections for use in design by second order inelastic analysis
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通过二阶非弹性分析进行设计时使用的等效弓形缺陷
DOI：
10.1016/j.istruc.2020.03.065
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发表时间：
2020
期刊：
影响因子：
4.1
通讯作者：
Walport F
中科院分区：
文献类型：
--
作者：
Walport F
受压构件的稳定性通常通过屈曲曲线来评估，该曲线包括初始几何缺陷和残余应力的影响。或者，通过使用考虑几何缺陷和残余应力的等效弯头缺陷进行弹性或非弹性二阶分析，可以更直接地获得承载力。对于二阶弹性分析设计，遵循EN1993-1-1的建议，可以对给定的构件反算等效弓缺陷的大小，以得到与构件屈曲曲线相同的结果，或者可以更简单地将其视为构件长度的固定比例。在这两种情况下，还需要随后的M-N(弯曲+轴向)横截面检查，检查可以是线弹性的，也可以是线塑料的。对于二阶非弹性分析设计，也称为具有缺陷的几何和材料非线性分析设计(GMNIA)，目前还没有合适的建议来确定当量弯头缺陷的大小，如本文所示，通常不适合使用基于弹性分析的当量弯头缺陷。因此，本文建立了适用于二阶弹塑性分析设计的等效弯头缺陷。用几何和材料非线性分析生成的基准有限元结果校准等效的弓缺陷，几何缺陷为L/1000(L为构件长度)和残余应力。在此基础上，提出了钢和不锈钢构件的当量弓缺陷幅值e0=αL/150(α是EC3中的传统缺陷因子)，并给出了准确的结果。采用EN1990提出的一阶可靠度方法，以有限元极限荷载为基准，对该方法的可靠性进行了评估，结果表明，钢材的部分安全系数为1.0，不锈钢的部分安全系数为1.1。
The stability of compression members is typically assessed through buckling curves, which include the influence of initial geometric imperfections and residual stresses. Alternatively, the capacity may be obtained more directly by carrying out either an elastic or an inelastic second order analysis using equivalent bow imperfections that account for both geometric imperfections and residual stresses. For design by second order elastic analysis, following the recommendations of EN 1993-1-1, the magnitudes of the equivalent bow imperfections can either be back-calculated for a given member to provide the same result as would be obtained from the member buckling curves or can be taken more simply as a fixed proportion of the member length. In both cases, a subsequent M–N (bending + axial) cross-section check is also required, which can be either linear elastic or linear plastic. For design by second order inelastic analysis, also referred to as design by geometrically and materially nonlinear analysis with imperfections (GMNIA) there are currently no suitable recommendations for the magnitudes of equivalent bow imperfections and, as demonstrated herein, it is not generally appropriate to use equivalent bow imperfections developed on the basis of elastic analysis. Equivalent bow imperfections suitable for use in design by second order inelastic analysis are therefore established in the present paper. The equivalent bow imperfections are calibrated against benchmark FE results, generated using geometrically and materially nonlinear analysis with geometric imperfections ofL/1000 (Lbeing the member length) and residual stresses. Based on the results obtained, an equivalent bow imperfection amplitudee0=αL/150 (αbeing the traditional imperfection factor set out in EC3), is proposed for both steel and stainless steel elements and shown to yield accurate results. The reliability of the proposed approach is assessed, using the first order reliability method set out in EN 1990, against the benchmark FE ultimate loads, where it is shown that partial safety factors of 1.0 for steel and 1.1 for stainless steel can be adopted.
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