Regresar

A real-life resiliency experiment: The Los Caras bridge of Ecuador

Abstract:

Resiliency after an extreme event was demonstrated by the performance of the Los Caras Bridge following the 2016 Mw7.8 Muisne earthquake. With a 2-km length main span, the Los Caras Bridge in the province of Manabí is the longest bridge in Ecuador. The project was designed and constructed by the Ecuadorian Army Corps of Engineers (EACE) using seismic protective Triple Friction Pendulum (TPF) isolation devices at each of the 152 bearings in the central section. While it is estimated that the ground accelerations may have reached 1 g at the bridge site, with possible soil softening or liquefaction phenomena, it remained fully functional with minimal, mostly aesthetic repairs needed. Rapid post-event inspections by the Army Corps team identified that some bearings experienced the largest-ever recorded deformation for a TPF device, reaching 65 cm at Pier 12. Following the earthquake, the bearing at Pier 12, where likely the accelerations exceeded design levels, showed no visible damage; however, following several EACE inspections, it was determined that Pier 12 was more flexible than expected during design due to low lateral support of the upper soil layers at that location, concluding that this pier should be replaced with a new installed TPF. This paper presents information about the Los Caras Bridge design, details of the subsurface conditions, the used seismic isolation system, observations of ground motion records in the site vicinity, and comparisons with contemporary design criteria. The post-Muisne EACE inspection results of Pier 12 and multiple other locations along the bridge are discussed, along with the protocol and procedures applied to replace the bearings at Pier 12. Finally, the importance of the proven performance of advanced seismic protective systems in this major infrastructure project that became a symbol of resilience with positive impact on the people of Ecuador that faced the devastation of a major earthquake is highlighted.