Keywords: steel frames, corrosion, simulation-based reliability assessment, Monte Carlo, simulations, reliability, safety.

The transition from the pre-computer era to the era of advanced computer technology leads to the introduction of qualitatively new probabilistic structural reliability assessment concepts. This paper focuses attention on the application of one of the advanced concepts, the simulation-based reliability assessment (SBRA) method applicable in codes and in designers' everyday work.

Using a pilot example the probabilistic safety, serviceability and durability assessment of steel planar frame structures according to the SBRA method [1] is explained and the assessment procedure is indicated. Special attention is paid to the modelling and evaluation of possible corrosion effects. All input variables are expressed using non-parametric distributions. The load effect combinations, the effects of global and local imperfections and the variation of mechanical and geometrical properties of individual structural components are evaluated using direct Monte Carlo technique [2]. The P-Delta and P-delta second order theory transformation model applied in order to evaluate the response of the structure to the load combinations leads to non-traditional local and global stability check. The safety, serviceability and durability criteria are checked by comparing the calculated probability of failure P_f and the target probability P_d. The calculation of the probability of failure P_f, referring to individual cross-sections, leads to a plot of so-called "probability of failure curves" [3]. Using the P_f-curves, it is very easy to identify sections in the structure with increased risk of exceeding the introduced reference value. A structural engineer so obtains an overview about the reliability level of particular components of the structure. It is also possible to utilize the P_f-curves for an optimization of the load carrying system.

The probabilistic assessment procedure was implemented in the new designed software MCD 1.2 that is used for the reliability evaluation of steel frame structures exposed to corrosion effects. The user interface is similar to common static software products. The program MCD 1.2 is not, in any case, a universal static software for probabilistic reliability assessment of steel structures exposed to corrosion. The main goal was to develop a user-friendly application that would indicate efficient utilization of probabilistic simulation-based methods in the sphere of reliability assessment of newly designed as well as existing steel structures exposed to corrosion.

1

P. Marek, M. Guštar, T. Anagnos, "Simulation-Based Reliability Assessment for Structural Engineers", CCR Press, Boca Raton, Florida, 1996.

2

P. Marek, et al., "Probabilistic Assessment of Structures using Monte Carlo Simulation. Background, Exercises and Software", (2nd edition), ITAM CAS, Prague, Czech Republic, 2003.

3

V. Krivý, P. Marek, "Zur probabilistischen Bemessung von Stahlrahmen", (in German), Stahlbau, v. 76, n. 1, p. 11-20, 2007.

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