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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Shear behavior of spliced post-tensioned girders

Moore, Andrew Michael, 1984- 24 October 2014 (has links)
By its nature a spliced girder must contain a number of post tensioning tendons throughout its length. The focus of the experimental program described in this dissertation is the evaluation of the strength and serviceability of post-tensioned girders loaded in shear, and, more specifically, how a post-tensioning duct located in the web of a girder affects the shear transfer mechanism of a bulb-tee cross-section. Due to the limited number of tests in the literature conducted on full-scale post-tensioned girders, eleven shear tests were performed on seven prestressed concrete bulb-tee girder specimens. Of these tests, ten were conducted on specimens that contained a post-tensioning duct within their web and additional pretensioning reinforcement in their bottom and top flanges. The remaining shear test was conducted on a control specimen that did not have a post-tensioning tendon but contained the same pretensioning reinforcement as the post-tensioned girder specimens. The behavioral characteristics of these eleven test specimens at service level shear forces and at their ultimate shear strengths were evaluated in regards to five primary experimental variables: (i) the presence of a post-tensioning duct, (ii) post-tensioning duct material (plastic or steel), (iii) web-width, (iv) duct diameter, and (v) the transverse reinforcement ratio. The findings of this experimental study are described in detail within this dissertation, but can be summarized by the following two points. (i) No differences were observed in the ultimate or service level shear behavior in girders containing plastic grouted ducts when compared to those containing steel grouted ducts and (ii) The current procedure of reducing the effective web width to account for the presence of a post-tensioning duct is ineffective because it addresses the incorrect shear transfer mechanism. A method that correctly addresses the reduction in shear strength due to the presence of a post-tensioning duct was developed and verified using the tests performed during this experimental program and tests reported in the literature. / text
2

Behavior of the cast-in-place splice regions of spliced I-girder bridges

Williams, Christopher Scott 17 September 2015 (has links)
Spliced girder technology continues to attract attention due to its versatility over traditional prestressed concrete highway bridge construction. Relatively limited data is available in the literature, however, for large-scale tests of post-tensioned I-girders, and few studies have examined the behavior of the cast-in-place (CIP) splice regions of post-tensioned spliced girder bridges. In addition to limited knowledge on CIP splice region behavior, a wide variety of splice region details (e.g., splice region length, mild reinforcement details, cross-sectional geometry, etc.) continue to be used in the field. In response to these issues, the research program described in this dissertation was developed to (i) study the strength and serviceability behavior of the CIP splice regions of spliced I-girders, (ii) identify design and detailing practices that have been successfully implemented in CIP splice regions, and (iii) develop design recommendations based on the structural performance of spliced I-girder test specimens. To accomplish these tasks, an industry survey was first conducted to identify the best practices that have been implemented for the splice regions of existing bridges. Splice region details were then selected to be included in large-scale post-tensioned spliced I-girder test specimens. Two tests were conducted to study splice region behavior and evaluate the performance of the chosen details. The failure mechanisms of both test girders were characterized by a shear-compression failure of the web concrete with primary crushing occurring in the vicinity of the top post-tensioning duct. Most significantly, the girders acted essentially as monolithic members in shear at failure. Web crushing extended across much of the test span and was not localized within the splice regions. To supplement the spliced girder tests, a shear-friction experimental program was also conducted to gain a better understanding of the interface shear behavior between precast and CIP concrete surfaces at splice regions. The findings of the shear-friction study are summarized within this dissertation. Based on the results of the splice region research program, design recommendations were developed, including recommended CIP splice region details.

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