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The paper is focused on the deterioration of industrial reinforced concrete chimneys caused by carbonation. It is considered that a chimney has to be repaired when more than 30% of its surface is affected by visible corrosion-induced cracks. An optimal maintenance strategy aims at the postponement of this state beyond the intended service life of the chimney with minimum maintenance costs.

The contribution is focused on quantifying model uncertainty of crack width estimates for reinforced concrete beams. Predictions obtained by the model provided by the fib Model Code 2010 are compared with results of tests of beams having different longitudinal and shear reinforcement ratios and concrete cover. Trends of model uncertainty with basic variables are investigated.

The contribution is focused on reliability of balcony girders of a Czech national heritage monument. As preliminary reliability assessment suggests insufficient resistance, a series of nondestructive tests supplemented by a single tensile test are performed and evaluated by the statistical methods. Values of material properties, recommended in standards for historic materials, seem to be overly conservative and it is advised to specify properties of historic metallic materials by tests.

The specification of risk and reliability acceptance criteria is a key issue of reliability verifications of new and existing structures. Current target reliability levels in standards appear to have considerable scatter. Critical review of risk acceptance approaches to societal, economic and environmental risk indicates that an optimal design strategy is mostly dominated by economic aspects while human safety aspects need to be verified only in special cases. It is recommended to specify the target levels considering economic optimisation and the marginal life-saving costs principle, as both these approaches take into account the failure consequences and costs of safety measures.

This paper is focused on the reliability analysis of an existing reinforced concrete bridge from 1908. The load bearing capacity is assessed in accordance with valid standards using updated partial factors and the partial factors for structural design. Load bearing capacities obtained by these methods are critically compared. The application of the updated partial factors leads to 15% higher load bearing capacity than the ordinary partial factor method used for structural design.

The target reliability levels recommended in national and international documents vary within a broad range, while the reference to relevant costs and failure consequences is mentioned only very vaguely. In some documents the target reliability index is indicated for one or two reference periods (1 year, 50 years or life-time) without providing appropriate links to the design working life. This contribution attempts to clarify the relationship between the target reliability levels, costs of safety measures, failure consequences, reference periods and the design working life

Parameter estimation uncertainty is often neglected in reliability studies, i.e. point estimates of distribution parameters are used for representative fractiles, and in probabilistic models. A numerical example examines the effect of this uncertainty on structural reliability using Bayesian statistics. The study reveals that the neglect of parameter estimation uncertainty might lead to an order of magnitude underestimation of failure probability.

Carbonation-induced corrosion is a degradation processes, which causes significant economic losses to the operators of an aging large, reinforced concrete (RC) structures such as cooling towers. Due to large variability of basic variables, the probabilistic approach is suitable to describe carbonation ingress. In this study, the probabilistic model is developed for service life assessments of large RC structures exposed to environmental effects. For existing structures, carbonation ingress in normally described using carbonation depth data from in-situ surveys. The shape of a time-dependent carbonation depth curve, essential for long-term predictions, is expressed through the weather function which accounts for the effect of environmental exposure of the structure. This study indicates how a probabilistic model of carbonation ingress can be established; numerical illustration is focused on existing cooling towers located in the Czech Republic. It appears that when long-term observations of carbonation depth are unavailable, the shape of a time-dependent carbonation depth curve can be determined on the basis meteorological data. [ABSTRACT FROM AUTHOR]

Thin-web steel girders are attractive to be used because of their efficiency in bending. For such girders, the issue of ensuring local buckling becomes very relevant. Calculation formulas in most cases are complex and have a limited scope of application. The calculations based on numerical models make it possible to consider all the specifics of the designed element more universally. The article deals with the calculation of the buckling of the web girder under the combination of patch and shear loading by finite element modelling. Numerical models have been created, and a comparative analysis with experimental results has been carried out. The presented principles for constructing FE models (mesh size, material model, etc.) are recommended to follow when analysing the resistance and behaviour of beams with a thin web. Sensitivity analysis of the FE model with respect to the input parameters revealed the most important parameters (yield strength of steel, web thickness, geometry), the uncertainty of which needs to be taken into account when creating FE models. The convergence of the results supports the use of the finite element method in the design of steel beams for a qualitative and quantitative assessment of resistance. However, further development of unified principles for creating FE models and their verification on a larger amount of experimental data is required, as well as the determination of partial factors considering the variability and uncertainties in the obtained results and specified reliability level. [ABSTRACT FROM AUTHOR]

This paper presents the comparison of advanced semi‐probabilistic methods for the design and assessment of concrete structures represented by mathematical models solved by non‐linear finite element methods. The special attention is given to the advanced methods focused on the estimation of the coefficient of variation of structural resistance. Numerical examples represent a replication of laboratory experiments of beams with different failure modes. The obtained results are discussed with respect to the accuracy of the employed methods and the influence of the assumed statistical correlation among basic variables. Simplified methods give a good estimation of the design values, though their accuracy is dependent on the type of the failure mechanism. Moreover, it is shown that mutual correlations among random variables may significantly affect the design value of resistance, and they should be carefully defined and modeled. [ABSTRACT FROM AUTHOR]

Non-linear finite element analysis (NLFEA) has become a widely used tool in the reliability verification of reinforced concrete (RC) structures. Reliability assessment of RC structures is a challenging task and simplified approaches to reliability verifications are needed to allow for routine applications. Simplified semi-probabilistic methods such as the partial factor method (PFM) or the Method of Estimation of Coefficient of Variation (ECoV) may yield over- or under-conservative approximations. This contribution investigates such errors related to the applications of these two methods to series systems; the design resistances obtained by the probabilistic approach are considered as a reference level. It appears that PFM provides good approximations as the method is focused on critical members in the cases under consideration. ECoV may overestimate up to 20% in situations where NLFEA based on mean and/or characteristic values fails to identify a dominating failure mode. The maximum observed error is attributed mainly to the failure in identifying the type of distribution of the system resistance. The presented limited analysis indicates several directions for further research (analysis of other types of structural systems, cases with non-lognormal resistances, effects of a number of system components, and their mutual correlations, and performance of advanced methods for reliability verification). Recommendations on how to identify situations when a significant error can be expected should be provided for practical applications of simplified semi-probabilistic methods. [ABSTRACT FROM AUTHOR]