Abstract
Fibre reinforced concrete (FRC) is increasingly used for structural purposes owing to its many benefits, especially in terms of improved overall sustainability of FRC structures relative to traditional reinforced concrete (RC). Such increased structural use of FRC requires safe and reliable models for its design in ultimate limit states (ULS). Particularly important are models for shear strength of FRC members without shear resistance due to the potential of brittle failure. The fib Model Code 2010 contains a model for the shear strength of FRC members without shear reinforcement and the same partial factor accepted for RC structures is accepted for FRC elements. This approach, however, is potentially on the unsafe side since the uncertainties of some design-determining mechanical properties of FRC (i.e., residual flexural strength) are larger than those for RC. Therefore, in this study, a comprehensive reliability-based calibration of the partial factor γc for the shear design of FRC members without shear reinforcement according to the fib Model Code 2010 model is performed. As a first step, the model error δ is assessed on 332 experimental results. Then, a parametric analysis of 700 cases is performed and a relationship between the target failure probability βR and γc is established. The results demonstrate that the current model together with the prescribed value of γc = 1.50 does not comply with the failure probabilities accepted for the different consequences of failure of FRC members over a 50-year service life. Therefore, changes to the shear resistance model are proposed in order to achieve the target failure probabilities.
Highlights
Significant advances in research on fibre reinforced concrete (FRC) over the last 20 years have led to its increasing use in structural applications
The results demonstrate that the current model together with the prescribed value of cc = 1.50 does not comply with the failure probabilities accepted for the different consequences of failure of FRC members over a 50-year service life
This paper presented a comprehensive reliabilitybased calibration of the partial factor cc for the shear design of FRC members without shear reinforcement according to the fib Model Code 2010 model
Summary
Significant advances in research on fibre reinforced concrete (FRC) over the last 20 years have led to its increasing use in structural applications. The differences in the model errors found between researchers can principally be attributed to the databases they used and their sizes as well as the values of residual strengths of FRC; e.g. Lantsogh [29] used an analytic expression to predict residual strength, whereas Cuenca et al [36] relied on experimentally reported values While these results are commensurable with model uncertainties for RC members without shear reinforcement, these are inconclusive about the reliability of SFRC shear design since the probability of failure remains unquantified. The aim of this study is to perform a probabilistic analysis of the MC2010 model for the shear strength of FRC members without shear reinforcement and calibrate partial factor cc required for achieving codeprescribed failure probabilities Pf according to different consequence classes For this purpose, first, the model error was determined on a database of experimental results. The results and conclusions presented are expected to provide a contribution for future revisions of the national and international design codes for FRC members, such as the currently ongoing efforts on the preparation of the fib Model Code 2020 [38]
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