Probabilistic Capacity Models for Corroding Posttensioning Strands Calibrated Using Laboratory Results

• Published in: Journal of engineering mechanics Vol. 135; no. 9; pp. 906 - 916
• Main Authors: Gardoni, Paolo, Pillai, Radhakrishna G, Hueste, Mary Beth D, Reinschmidt, Kenneth, Trejo, David
• Format: Journal Article
• Language: English
• Published: Reston, VA American Society of Civil Engineers 01.09.2009
• Subjects: Applied sciences; Bridges; Buildings. Public works; Concrete bridges; Corrosion; Corrosion mechanisms; Exact sciences and technology; Fracture mechanics (crack, fatigue, damage...); Fundamental areas of phenomenology (including applications); Metals. Metallurgy; Physics; Solid mechanics; Structural and continuum mechanics; Suspension bridges. Stayed girder bridges. Bascule bridges. Swing bridges; TECHNICAL PAPERS; Time frequency domain method; Structural reliability; Test bar; Modeling; Voids; Cavity; Stayed girder bridge; Capacity; Chlorides; Humidity; Water content; Tension; Strand; Bayes estimation; Probabilistic approach; Ducts; Large pipe; Rupture; Probability; Experimental study; Florida; Posttensioning; Bridges; Corrosion; Concrete construction; Wire rope; Porosity
• ISSN: 0733-9399; 1943-7889
• DOI: 10.1061/(ASCE)EM.1943-7889.0000021

The presence of air voids, moisture, and chlorides inside tendons or ducts was cited as a reason for the early age strand corrosion and failure in the Mid-bay, Sunshine Skyway, and Niles Channel posttensioned (PT) bridges in Florida, United States. Although rare, these incidents call for frequent inspection and structural reliability assessment of PT bridges exposed to moisture and chlorides. This paper develops and presents probabilistic strand capacity models that are needed to assess the structural reliability of such PT bridges and recommends a time frequency of inspection. A total of 384 strand test specimens were exposed to various void, moisture, and chloride concentration conditions for 12 and 21 months; the remaining tension capacities were then determined. Using this experimental data and a Bayesian approach, six probabilistic capacity models were developed based on the void type. The mean absolute percentage errors of these models are less than 4%, indicating that reasonably accurate prediction of the strand capacity is possible, when void, aggressive moisture, and chloride conditions are present.