Structural health monitoring method for curved concrete bridge boxgirders

摘要

Curved concrete bridge girders have very complex internal forces, stress and strain distribution. As a consequence oftheir shape, not only the usual bending moments and shear forces are generated, but also important torsion moments arecreated. These moments "rotate" the axes of principal tensional stresses increasing the risk of cracking. Post-tensioningcan prevent the cracks, but the added compression forces introduced in different directions increase the complexity ofstress and strain fields. Therefore, the curved post-tensioned concrete girders must be particularly designed and carefullyconstructed. However, the real structural behavior should be verified, and risks and uncertainties related to structuraldesign and quality of construction minimized. Structural health monitoring is a natural solution for these issues.Structural health monitoring method, based on the use of fiber optic interferometric technology including long-gagesensors and inclinometers, is presented in this paper. A 36 meters long curved post-tensioned bridge box girder isequipped with so-called parallel and so-called crossed sensor topologies, and inclinometers, in order to monitor axialstrain, both horizontal and vertical curvature changes, torsion, average shear strain and rotations in both vertical plans.Important parts of structure life such as construction, post-tensioning and first years of service are registered, analyzedand presented.