Damage tolerance of the prestressing steel in a bridge stay-cable after thirty years of service in a graded, extremely adverse environment

Abstract

The paper assesses the damage tolerance of the presstressing steel composing a 30 m-long bridge stay-cable subjected for decades to the singular environmental conditions originated at a hidden fault, which behaved as a latent defect and produced the sudden failure of the stay cable 30 years after construction. The structural design of the bridge was redundant, meaning that the failure did not entail consequences other than those derived from taking it out of service for inspection and subsequent repair to restore its structural and functional integrity. Removal of the failed stay-cable provided a hardly repeatable opportunity of analyzing and correlating the tensile behavior, deterioration condition and damage mechanisms of the component strand-wires. The latent defect created a graded-adverse environment for the prestressing steel, which produced a damage gradient high enough to supply a wide-ranging series of samples for the exhaustive assessment of its damage tolerance. The instrumented tensile testing and scanning electron microscopy (SEM) analysis of these samples allowed assessment on a comparative basis, comprising tensile behavior and damage mechanisms, and providing highly encouraging results as to the contribution of prestressing steel to the structural integrity of the stay-cables.