Impact of half‐joint failures on RC girder bridges: A robustness quantification study

The robustness of bridge structures is critical to ensuring safety and service continuity, particularly in aging infrastructure exposed to degradation and unexpected loads. Reinforced concrete (RC) half-joint bridges—widely built in Italy between the 1950s and 1970s—exhibit specific vulnerabilities due to inspection challenges, durability concerns, and susceptibility to progressive collapse. Although increasingly studied, the literature lacks comprehensive robustness assessments accounting for full nonlinear system behavior under local damage. This study addresses this gap by developing a refined finite element (FE) modeling approach to simulate the global response of RC half-joint bridges following localized damage. The model includes material nonlinearities throughout the structure and evaluates robustness indicators using a notional removal strategy. The methodology is applied to the Annone viaduct, which collapsed in 2016 in northern Italy. The case study serves to analyse failure mechanisms linked to Gerber saddles. Results demonstrate the effectiveness of robustness indicators in capturing force redistribution and progressive collapse in half-joint bridges. The study offers insights into beam–slab interaction and shows how numerical models can support risk-based maintenance and decision-making. The proposed framework enhances assessment strategies for structurally critical bridges and supports future monitoring and mitigation guidelines.