Evaluation of the True Behaviour of the End Supports in the Carbajal de La Legua Old Bridge

Bridges are prone to bearing deterioration due to environmental causes or traffic overloading. For example, a bridge originally designed as simply supported may be behaving differently due to bearing aging and deterioration. The latter can lead to damage, not only to the bearings, but also to the rest of the structure. In this paper, load testing is used to evaluate the true behavior of the boundary conditions of an existing bridge and how they affect the overall structural response. For this purpose, a 16 m span concrete bridge is subjected to the forces applied by a truck loaded with quarry aggregate. Static measurements are obtained for several positions of the vehicle while dynamic ones are also
obtained as the truck crosses the bridge at speed. These data is used to tune a 3D finite element model until achieving an accurate resemblance with the measurements. Boundary conditions are idealized with linear springs, which allow to consider all possible scenarios at both ends. Finally, spring constants that best fit the measurements are used to measure the impact of the boundary conditions on the distribution of internal forces in the structure.