Uncertainties of Crack Width Models

Červenka, Vladimír; Marková, Jana; Mlčoch, Jan; Caldentey, Alejándro Pérez; Sajdlová, Tereza; Sýkora, Milan

doi:10.1007/978-3-319-59471-2_190

Cited by 6 publications

(6 citation statements)

References 8 publications

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“…The bias in the EC2 model predictions for mean crack width is slightly less than two and the coefficient of variation reduces to 0.25 for crack width levels of 0.4 and 1 mm. The recent study [6] shows that crack widths can by well predicted by FEM. However, uncertainty in maximum crack width estimates seems to be in all cases much larger than that related to the models for Ultimate Limit State verifications [7].…”

Section: Crack Width Model Based On MC 2010mentioning

confidence: 93%

Uncertainty in Crack width Estimates According to Fib Model Code 2010

Mlčoch¹,

Marková²,

Sýkora³

2017

Transactions of the VŠB – Technical University of Ostrava, Civil Engineering Series.

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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. KeywordsCrack width, model uncertainty, concrete cover, reinforcement ratio.

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Section: Crack Width Model Based On MC 2010mentioning

confidence: 93%

Uncertainty in Crack width Estimates According to Fib Model Code 2010

Mlčoch¹,

Marková²,

Sýkora³

2017

Transactions of the VŠB – Technical University of Ostrava, Civil Engineering Series.

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“…The value of V E considered in this study can be related to EN 1992 (Equations and ) and model uncertainty from a related contributions . If a different predictive model, for example, Model Code 2010 should be considered, the resulting action‐effect distribution may take on different value, yet in a reasonable range as shown by a different study.…”

Section: Example: Water Retaining Structurementioning

confidence: 99%

“…Moreover, model uncertainty may be viewed just as important parameter in obtaining the required reliability level. The influence of high model uncertainty can be mitigated by the use of advanced simulations such as nonlinear FE models where the simplified approach offered by the code is replaced by a refined analysis and model uncertainty can be therefore reduced.…”

Section: Example: Water Retaining Structurementioning

confidence: 99%

A comparative study of target reliability index derivation for reinforced concrete structures governed by serviceability limit state

Lenner

Viljoen

Nierop

2018

Structural Concrete

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Typical design of reinforced concrete structures is governed by the ultimate limit state (ULS), while serviceability limit state (SLS) is checked. The target reliability index for ULS is recommended based on cost optimization and back calibration of existing practice. Many design cases, such as prestressed concrete, are, however, governed by serviceability conditions and the background for the current recommendations for target reliability index of irreversible SLS as provided by ISO 2394 is unclear. This contribution reviews previously developed generalized framework for determination of SLS target reliability by taking into account a cost ratio and statistical parameters of action‐resistance variable. Target reliability index βt,SLS can be then obtained from the previously introduced table with a minimum effort. A case‐specific approach to the cost optimization with FORM analysis is introduced in order to validate the results of the generic approach. It is found that there is a discrepancy in terms of the obtained value of target reliability index. This can be attributed to the influence of the decision parameter d in the cost optimization process. It affects the probability of failure pf(d) at the different rates for different formulations of SLSs. The nearly linear assumption in the generic formulation may not necessarily apply in other cases, and care should be taken when specifying target reliability index βt,SLS as the effectiveness of the decision parameter must be observed.

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“…o μ θ = 0.90 and V θ = 0.30 for long-term loading (n = 25).  The same authors [2] investigated flexural crack widths: o μ θ = 1.16 and V θ = 0.51 for short-term loading (n = 620) -note that Cervenka et al [5] obtained μ θ = 1.1 and V θ = 0.35 for short-term flexural crack widths predicted by FEM. o μ θ = 1.42 and V θ = 0.34 for long-term loading (n = 50).…”

Section: Probabilistic Verificationmentioning

confidence: 99%

“…The FEM analysis can take into account more realistic stress distribution for given structural geometry and also time-dependent effects of initial strain development due to temperature, shrinkage, and creep. Consequently, unbiased estimates of crack widths are obtained and dispersion of model uncertainty reduces [5]. To indicate the scope of application of engineering and FEM approaches and reach the balance between model and input parameter uncertainties, the analysis of their model uncertainties and sensitivity analysis with respect to effects of basic variables is needed.…”

Section: Fem Predictionsmentioning

confidence: 99%

Towards Optimum Design for Crack Width Limit States: The Need for Further Developments

Sýkora

Holický

Marková

2018

WIT Transactions on the Built Environment

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Serviceability limit states including cracking are of increasing importance and often dominate the design of reinforced concrete structures. Furthermore, actual crack widths and their shape play an important role in the assessment of service life of existing reinforced concrete structures. Crack width is inherently a random variable of considerable scatter due to randomness of material properties, geometry of the structure, loading and model uncertainty in crack width estimates. The state-of-the-art concepts for serviceability verifications were recently presented in fib Model Code 2010 that is jointly with Eurocode EN 1992-1-1 considered as key background materials in this study. To assess the sufficiency of code requirements and design procedures, crack widths of water retaining structures are investigated in detail using probabilistic methods of structural reliability. The current codes seem to be well calibrated to reach a target reliability index of 1.5 in the serviceability limit states. The two variables dominating structural reliability are uncertainty in crack width model and concrete cover. Numerous topics need to be further investigated including revision of crack width limits, improvements of mechanical models, quantification of model uncertainty, methodology for load combinations, treatment of spatial variability for large structures, and optimisation of target reliabilities.

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Uncertainties of Crack Width Models

Cited by 6 publications

References 8 publications

Uncertainty in Crack width Estimates According to Fib Model Code 2010

Uncertainty in Crack width Estimates According to Fib Model Code 2010

A comparative study of target reliability index derivation for reinforced concrete structures governed by serviceability limit state

Towards Optimum Design for Crack Width Limit States: The Need for Further Developments

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