Semester

Fall

Date of Graduation

2008

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

Julio F. Davalos

Committee Co-Chair

Indrajit Ray.

Abstract

In 2006, the Federal Highway Administration statistics showed that approximately one out of every 13 reinforced concrete bridges in the USA is structurally deficient. As infrastructure continues to age and deteriorate, there will not be sufficient funds to replace every deficient bridge. Therefore, effective and durable repair methods must be developed and implemented. In this research, an experimental study is presented to determine both the short- and long-term efficiencies of concrete retrofit with externally-bonded carbon fiber reinforced polymer (CFRP) fabrics. The primary objective is to determine effective concrete-repair and CFRP-retrofit approaches for rehabilitation of deteriorated concrete bridge girders, based on potential for long-term durability and costs. This two-part study consisted of 35 large-scale reinforced concrete beam specimens. Part I consisted of 14 beams with dimensions 6x8x108" and Part II consisted of 21 beams with dimensions 6x8x78". The beams were cast using chloride contaminated, low-strength and highly porous concrete; and they were aged using an induced electric current technique. Supplementary tests were also conducted on specimens and materials, including cylinder compression, rebound hammer, ultrasonic pulse velocity, FRP-concrete pull-off, FRP direct tension, and crack measurement.;In Part I two substrate repair methods were compared, epoxy crack-injection and complete replacement of concrete cover using polymer-modified concrete, and long-term durability was studied by inducing additional corrosion after repair. In Part II the performance of three unique FRP anchorage schemes were compared under both static and cyclic loading. Scheme 1 consisted of only flexural FRP without anchors, scheme 2 consisted of only two strategically placed anchors on each beam, and scheme 3 consisted of eight anchors evenly spaced along each span. In Part I, it was found that polymer concrete patch repair with corrosion inhibitors was by far the most durable substrate repair method, although all beams experienced further deterioration and loss in strength upon additional corrosion. In Part II, there were not significant differences in load capacity, deflection, or stiffness among the three anchoring schemes. The fatigue cyclic loading affected the failure mode of the beams. The accelerated corrosion process used in this research was adjusted using trial beam samples, and became successful and dependable in producing consistently artificially-aged specimens. This research provided further insight into future bridge rehabilitation and contributed to practical guidelines for concrete patch-repair and CFRP retrofit of concrete girders, to assure long-term adequate performance under environmental and mechanical loads.

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