Time-Dependent Deformations in Segmental Prestressed Concrete Bridges
Marshall, Vernon
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Permalink
https://hdl.handle.net/2142/66900
Description
Title
Time-Dependent Deformations in Segmental Prestressed Concrete Bridges
Author(s)
Marshall, Vernon
Issue Date
1981
Department of Study
Civil Engineering
Discipline
Civil Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Civil
Language
eng
Abstract
A rational analytical procedure for estimating the time-dependent behavior of segmental prestressed concrete bridges built by the cantilever method was presented. This analytical procedure was aimed specifically at those bridges where segments are precast and adjacent cantilevers are made continuous. It was based on a step-by-step numerical procedure which attempts to account for most of the important parameters that influence the time-dependent behavior of these structures, and was incorporated in a computer program.
A procedure for estimating the creep of concrete subjected to a varying state of stress was introduced. This procedure was intended primarily for use when a limited number of experimentally determined specific creep curves are available, and was based on both the rate of creep method and the method of superposition.
In order to gauge the effectiveness of the analytical procedure introduced in this study, the Kishwaukee River Bridge was analyzed and the results compared with measured deformations of the structure. The structure was analyzed using material properties for concrete as experimentally obtained from outdoor stored and laboratory stored specimens, and those prescribed by the recommendations of the European Concrete Committee (C.E.B.)
The comparison of calculated and measured concrete strains indicated that shrinkage had the dominating effect on the development of the time-dependent strains. It was only the analysis that made use of concrete material properties obtained experimentally from outdoor stored specimens which correctly predicted the time-dependent development of concrete strains in the structure because the seasonal variation of shrinkage was correctly included in this analysis. The results of this analysis were in close agreement with measured strains.
The time-dependent changes of prestressing force, concrete stress and bending moment obtained from the time-dependent analyses of the Kishwaukee River Bridge were presented and discussed to illustrate some of the characteristics of the time-dependent behavior of this structure. These quantities were found to be relatively insensitive to the material properties assigned to the concrete, as opposed to the time-dependent deformations which were found to be highly sensitive to the concrete material properties.
The effects on the time-dependent behavior of the Kishwaukee River Bridge of actual loads applied during the construction of the structure were investigated and were found to be negligible for practical purposes.
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