A Reliability-Based Assessment and Design Calibration of the Modified Strut-and-Tie Model for Steel Fiber Reinforced Concrete Deep Beams

A reliability analysis is performed on a modified Strut-and-Tie Model (STM), which accurately predicts the shear capacity of Steel Fiber Reinforced Concrete (SFRC) deep beams. However, inherent uncertainties are not considered when calculating the model's performance. This study implements a reliability analysis using Monte Carlo Simulation (MCS) on a dataset of 22 large-scale experimental samples, including samples with a simple supported and a two-span continuous configuration. In addition, a limit state function was established based on the modified STM model. Specifically, the analysis quantified the inherent safety of the uncalibrated model, revealing a reliability index (β) between 0.5 and 2.0. A reliability-based calibration was performed to address the issue of its composition not conforming with modern codes. For the Load and Resistance Factor Design (LRFD) format, a resistance factor (φ) of 0.50 was calculated, ensuring that different beam configurations achieve a consistent target reliability level.