SENSITIVITY ANALYSIS OF THE ULTIMATE RESISTANCE OF STEEL PLANE FRAMES TO IMPERFECTIONS

Abstract eng:
In research prioritization is on which imperfection is most deserving of further additional analysis or measurements on steel plane frames. Methodology based on Sobol’s variance is used for the sensitivity analysis. Input imperfections are of random origin. Geometrical nonlinear finite element solution is used systematically within the Monte Carlo framework, such that input uncertainties are always propagated through to the output. Majority of the input imperfections were measured and their random realizations computed using their histograms whilst employing the Monte Carlo method. The output random quantity is the load carrying capacity of the frame. The influence of initial imperfections on the load carrying capacity of frames with (i) columns under tension and (ii) columns under compression is illustrated. In the case of (i) the interactions of higher orders between input variables have a significant influence on the load carrying capacity. The influence of these interactions is quantified using Sobol’s sensitivity higher order indices. The dominant input variables are identified. In the event of (ii) the dominant variable is represented by system imperfections, which is burdened with high epistemic uncertainty. The fuzzy analysis of the influence of epistemic uncertainty of system imperfections on the uncertainty of the load carrying capacity is worked out at the end of this article.

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