Date of Graduation

12-2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Civil Engineering

Advisor/Mentor

Hale, W. Micah

Committee Member

Heymsfield, Ernest

Second Committee Member

Spearot, Douglas E.

Third Committee Member

Martí-Vargas, Jose R.

Keywords

Applied sciences; Bonds; Cracks; Development length; Pretensioned cooncrete; Strand bonds; Transfer length

Abstract

This research examines the relationship between concrete compressive strength and strand bond. The goal of this research was to develop an equation that relates strand bond to concrete compressive strength at strand release (approximately 1 day of age) and at 28 days of age, and those equations are presented in this investigation. Strand bond is assessed by measuring the transfer length and development length for prestressed beams cast in the laboratory. In the U.S., strand bond is predicted using transfer length and development length equations provided by the American Concrete Institute (ACI-318) Building Code and American Association of State and Highway Transportation Official (AASHTO) LRFD Bridge Design Specifications which were developed based on the 1950´s investigations. The equations provided by both ACI and AASHTO do not address concrete strength while equations, developed in this investigation, do account for the compressive strength of concrete at release and testing time. Although there has been much research conducted in this matter, this research provides a reliability data analysis relating to transfer and development lengths of prestressed concrete beams. Unlike many of the previous programs, this research includes strands of a known quality, the largest database of test specimens, and a variety of concrete mixtures and concrete strengths. This research concludes with the development of an analytical model to predict transfer length which includes concrete strength at release with fracture propagation around the strand.

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