Response and Failure of Los Grillos Bridge to a Slow-Moving Landslide

Abstract A reconnaissance mission was organized by the American Concrete Institute, Committee 133, to visit the Los Grillos Bridge in Colombia on September 13, 2023. The bridge is a post-tensioned cast-in-place segmental cantilever structure featuring a box girder spanning 180 m. Situated on a slow-moving landslide, the bridge failed on August 20, 2023. Analyses indicated that the concrete crushing of the bottom slab of the 180-m-long box girder triggered the failure. This case study demonstrates that similar structures can withstand large relative deformations in the transverse direction and differential settlements, yet they remain quite vulnerable to displacement in the longitudinal direction. It also highlights the susceptibility of bridge structures in unstable geological regions.