Analiza wrażliwości geometrycznie niedoskonałej jednopiętrowej konstrukcji szkieletowej ze stali – porównanie dwóch trybów obciążenia

Abstrakt

"In this study, two methods to numerically analyse a single-storey vertically loaded steel frame structure with initial geometrical
imperfections are compared. The first method is deterministic, where the initial imperfections, sway of the frame and local bow
imperfections of the columns are based on the corresponding European standard to design steel structures, Eurocode 3 (EC3).
The second, probabilistic method, where the imperfections are defined by the random stochastic parameters is using the first
order reliability method (FORM) along with numerous numerical finite element analyses in order to estimate the ultimate
resistance of the structure. In this FORM method, the statistical values of these input imperfections are derived from the
European standard for allowed erection and manufacturer tolerances, and these data corresponds with the experimentally
measured imperfections on real structures. Material parameters, as Young’s modulus and yield stress are also considered as
stochastic variables. Design ultimate resistance based on EC3 is compared with the 0.1% quantile of the stochastic ultimate
resistance of the FORM method. In general, assumptions of the deterministic EC3 approach are sometimes considered as
overly conservative. The main objective of this study is to verify and evaluate these assumptions by comparison with more
precise probabilistic method. Moreover, for both methods (EC3 and FORM), the resistance is determined under two loading
modes, one by increasing of the force load, the other by prescribed displacement. The loading conditions of these two loading
modes are applied analogically to each other, hence similar resistances for the corresponding method are expected. However,
this assumption needs to be verified within the probabilistic analysis conditions, what is the secondary objective of this paper."