Development of a probabilistic finite element model for the validation of strut-and-tie models in half-joint girders

Discontinuity regions in concrete structures, such as half-joints, exhibit complex stress distributions that challenge traditional design approaches.This study presents a probabilistic assessment of the structural capacity of a concrete half-joint by comparing strutand-tie models (STMs) with detailed finite element models (FEMs), taking into account parameter uncertainties.A validated 3D FEM is employed as a benchmark to evaluate the conservative nature of the STM and to compare the reliability index and failure probability.These are calculated using Latin Hypercube sampling in combination with the FEM simulations or the STMs and the first-order reliability method (FORM) and by using the FORM directly in combination with the STMs.Results show that the STM provides a safe lower bound estimate of capacity, but with some margin for improvement, particularly if the models are applied for assessment situations.A significant overexceedance of the probabilistically calculated reliability index with respect to its target design value and the corresponding conservativeness of the designed structure is observed.Further, distinct failure mechanisms observed in the FEM simulations highlight the limitations of STMs in capturing post-yield behaviour and load redistribution.This work underscores the potential of probabilistic FEMs as a validation tool for the calibration of simplified STM-based approaches and stresses the advantages and shortcomings of the current state-of-the art application of these approaches.