Thesis (M.S. in Engineering)--University of Texas at Austin, 2004. / Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (M.S. in civil engineering)--Washington State University, May 2006. / Includes bibliographical references (p. 147-151).

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

Recent findings regarding corrosion of post-tensioned bridges have highlighted the urgent need to develop reliable methods to predict the behavior of the structural system after damage has occurred and inspection techniques to assess the condition of the structure. Corrosion in strands is undesirable in that it often progresses without visual signs of distress, but may cause a brittle failure. To complicate the inspection, access to the strands for visual inspection is usually blocked by the concrete cross section. To date, significant efforts have been taken to improve the durability of the post-tensioned bridges. However, the behavior of the post-tensioned bridges with corrosion damage is not clearly understood and the currently available inspection techniques tend to provide only limited information about the nature and extent of the damage. The research project discussed in this dissertation was developed is to evaluate the feasibility of using the vibration technique to detect and estimate the extent of damage in an external tendon due to corrosion. To accomplish this goal, damage was induced in five specimens, which were monitored periodically to correlate the measured changes in the frequency response to the level of damage. The induced damage simulated the degradation of a post-tensioned structure from corrosion. This dissertation describes the experimental program and the numerical scheme used to estimate the condition of the specimens. Three types of specimens were tested during the experimental phase of the research: individual strands, cables specimens, and external tendons. A series of tension tests of individual strands were conducted to investigate changes in the uniaxial behavior after damage was induced. Simulated damage included uniform corrosion of the strand, mechanical wire cuts, and an initial defect in one wire. Three cable specimens and one tendon specimen were subjected to fatigue loading. The loading was selected to simulate the loss of cross-sectional area in the strands, and also caused grout damage. The frequency response of the specimens was recorded periodically during the fatigue tests and acoustic sensors were used to detect the occurrence of wire breaks. A second tendon specimen was exposed to an acid solution to simulate the hydrogen induced cracking in the strand at three different locations along the length of the specimen. A number of wires fractured during the exposure test and damage was inspected visually. Natural frequencies were also measured periodically. The residual prestressing force in of the specimens was extracted from the measured natural frequencies. The stiff string model was used to determine optimum values of tension and flexural stiffness from the frequency response. The numerical results from this optimization demonstrated the feasibility of using the vibration technique as a nondestructive testing method for external tendons.

published_or_final_version / abstract / Civil Engineering / Master / Master of Philosophy

Not available / text

Flexible fillers has recently been implemented as corrosion protection for post-tensioning tendons used in bridge structures in Florida. There are two different explanations why corrosion could take place: 1. water is able to reach the steel 2. Microbiologica l ly Influenced Corrosion. The aim of this research is to evaluate corrosion protection effectiveness of five differe nt microcrystalline waxes under different environmental conditions. Specimens tested ranged from 7-wire steel strands to single wires (12-16 cm). Another aim is the appraisal of wax degradation by fungi species. Single wires coated with each of the investigated protection materials, were sprayed with suspensions of three different fungi species and a mix of them. For single wires, independent of the environmental condition the specimen with more corrosion was Nontribos, as well as the filler coated wires contaminated with Fungi. Fungi species investigated were able to utilize the waxes as carbon source and caused differe nt extents of MIC. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection