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Title:Flexural distress and degradation mechanisms in pretensioned concrete beams and railroad crossties
Author(s):Cesar Bastos, Josue
Director of Research:Barkan, Christopher P. L.; Edwards, J. Riley
Doctoral Committee Chair(s):Barkan, Christopher P. L.
Doctoral Committee Member(s):Tutumluer, Erol; Lange, David A; Rizos, Dimitris C
Department / Program:Civil & Environmental Eng
Discipline:Civil Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Prestressed concrete
concrete crossties
concrete sleepers
flexural distress
concrete degradation
cyclic loading
water damage
Abstract:Crossties (sleepers) are an essential component of ballasted railroad track and concrete is a commonly used material for crossties in demanding locations such as heavy axle load (HAL) freight railroads, high-speed rail lines, and rail transit systems. Concrete crossties are often designed as prestressed concrete beams, but their use in the track structure differs greatly from other prestressed concrete beam applications. Although such beams are typically safety-critical structural components, individual concrete crossties can fail with relatively low risk to railroad operating safety. Consequently, crossties can continue to function satisfactorily despite some degree of deterioration. This can be accounted for in both design and maintenance practices. If flexural distress can be properly controlled, more economical crosstie designs combined with proper track maintenance practices may greatly benefit the overall railroad efficiency. Analytical and laboratory procedures were used to characterize the flexural distress of prestressed concrete beams and determine how the presence of water in cracks affects their degradation under repeated loading. North American crossties are rarely post-tensioned, so the principal focus was on pretensioned concrete. This dissertation describes research on the following topics: a flexural characterization of crossties, including a derivation of a statistical model for expected center-negative bending capacity; identification of damage mechanisms in pretensioned beams due to interaction of water with cracks through testing of multiple working hypotheses; and a stress estimation method for cracked pretensioned beams that serves as a tool for cyclic loading damage estimation, which is a novel application of section analysis of concrete beams. Experimental results showed little variability in the performance of North American crosstie designs, which often have high reserve flexural capacity and stiffness. Cyclic loading tests indicated accelerated deterioration in the presence of water, likely due to hydro-abrasion. Concrete deterioration led to flexural failure even when cracks were in the tensile region, which is attributed to loss of the tendon-concrete bond and the change in concrete properties in water. The novel procedures described in this dissertation will also contribute to improved practices of design, testing, and maintenance of concrete crossties and similar pretensioned concrete beams. These findings will contribute to advancing the development of mechanistic-empirical design processes for railway track components.
Issue Date:2020-04-24
Rights Information:Copyright 2020 Josué César Bastos
Date Available in IDEALS:2020-08-27
Date Deposited:2020-05

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