Resistance partial factor calibration for SFRC elements without shear reinforcement subjected to punching shear according to EN 1992-1-1:2023

Punching shear failure is often the governing design criterion of flat slabs at Ultimate Limit State and may potentially lead to progressive collapses. The latest version of Eurocode 2 (EN 1992–1–1:2023) introduces a new punching shear design model for fibre reinforced concrete (FRC) slabs in its Annex L. According to this approach, the concrete and shear reinforcement contributions are estimated based on the Critical Shear Crack Theory and the beneficial influence of the fibres is considered by means of the residual tensile strength of FRC. The model of EN 1992–1–1:2023 moves towards more rational approaches based on physical models. However, it appears that the reliability and applicability of the new formulation require further validation and calibration, particularly regarding the fibre contribution to the shear resistance. This paper is addressed at this topic, in an effort to provide a consistent safety format and calibrated values of the partial factors for the punching shear resistance of FRC. To that aim, an extensive literature review was conducted compiling a comprehensive database of steel fibre reinforced concrete (SFRC) slab-column connections without shear reinforcement. A total of 261 tests from 29 studies were collected. This database was subsequently filtered, considering only specimens with usual amounts of fibres and dimensions in construction, resulting into 67 representative tests. This database was later used to perform a probabilistic reliability-based calibration of the resistance partial factor associated with the fibre contribution γ V,FRC consistent with the FORM principles. The calibration considered different levels of scatter in the residual tensile strength of FRC, along with the target reliability index prescribed in the Eurocodes. The results show that a value of the resistance partial factor for the fibre contribution γ V,FRC equal to 1.30 may be adopted for expected scatters in the residual tensile strength of FRC up to 20 %, covering a wide range of practical applications. For higher levels of scatter, up to 30 % as a reasonable estimate of the maximum acceptable scatter in typical applications, a value γ V,FRC = 1.40 is suggested. For other cases, with even higher scatter or outside the range of parameters analysed, a detailed reliability analysis might be required. • Database of 261 tests compiled, subset of 67 used for reliability calibration of SFRC punching shear model in EN 1992-1-1:2023. • Study confirms EC2 safety format but proposes adjusted partial factors for fibres to align with target reliability levels. • Probabilistic calibration supports adjusted partial factors for fibres, based on SFRC variability, to meet reliability goals. • EN 1992-1-1:2023 punching shear model shows consistent accuracy and low variability versus experiments, confirming applicability.