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Use of 0.7-in. Diameter Prestressing Strand in Bridge Girders: Bond Behavior and Girder Stability

Alabdulkarim, Abdullah (2021) Use of 0.7-in. Diameter Prestressing Strand in Bridge Girders: Bond Behavior and Girder Stability. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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In prestressed concrete bridge girders, the use of 0.7-in. diameter strand will allow 35% increase in prestressing force than 0.6-in. diameter strand and 92% increase than 0.5-in. diameter strand. This increase in prestressing force will theoretically permit longer span lengths, shallow girders or fewer girders across the width of a given bridge. AASHTO bridge design and construction specifications do not specify the use of 0.7-in. diameter strands for precast prestressed girders. Lack of data on the use, and particularly the bond behavior, of 0.7-in. diameter strand prevent its wide use in bridge construction. In this thesis the bond behavior of 0.7-in. diameter strand is evaluated. In addition to geometric and material characterization, five strands of each diameter (0.5, 0.6 and 0.7-in.) were tested to evaluate the Hoyer effect. Test results indicate that the dilation ratio of the strand exceeds that predicted by the Poison ratio alone. A parametric investigation using the finite element method was conducted to evaluate the effects of strand dilation over the expected transfer length of the strand. Single-strand models were used to illustrate the Hoyer effect and four-strands models to investigate the effect of strand spacing. Potential for local cracking resulting from the Hoyer effect is identified.
Thirty beam-end specimens having straight and 90o hooked anchorages with different embedment lengths in different weight concretes were tested to evaluate the relative bond capacity of the strands. Test results indicate a predictable variation in bond behavior not attributed to the strand size. All tests exhibited shorter development lengths (i.e., better bond) than that prescribed in design. The potential benefits of hooked anchorage are identified in resisting high longitudinal tensile forces related to beam-end shear effects.
With the potential for longer girders, stability is a concern during all the stages of girder construction and erection. A few previously designed girders that had been optimized for length are evaluated for stability following the PCI method. Analysis indicated that stability generally could be achieved. When necessary, increasing the width of the top flange since Iy/Ix has the pronounced effect on improving stability.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Alabdulkarim, AbdullahAAA209@PITT.EDU
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairHarries,
Committee MemberShahrooz,
Committee MemberKhazanovich,
Committee MemberLin,
Date: 13 June 2021
Date Type: Publication
Defense Date: 12 January 2021
Approval Date: 13 June 2021
Submission Date: 15 March 2021
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 219
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Civil and Environmental Engineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: girder design; long girders; debonded strands; Abaqus simulation; smeared crack concrete; construction safety
Date Deposited: 13 Jun 2021 18:16
Last Modified: 13 Jun 2021 18:16

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