Use of CFRP Overlays to Repair Fatigue Damage in Steel Bridge Girders and Components

Abstract

Fatigue damage in steel girder bridges built prior to the mid-1980s is common due to distortion-induced fatigue. Different repair techniques have been developed and implemented to retrofit bridges of this era with existing fatigue damage. An experimental and analytical evaluation was conducted on the use of Carbon Fiber Reinforced Polymer (CFRP) as an alternative repair technique. Experimental testing was conducted on component specimens tested under pure tension loading conditions. Comparisons between specimens were based on the axial stiffness of the repaired specimen, a method commonly used in the Aerospace Engineering field. The analytical evaluation comprised of a suite of Finite Element models. A simplified steel girder section was modeled with two main objectives. The first was to evaluate the effect of bending and cross-frame forces on fatigue-crack location. The second was to compare the use of CFRP overlays as a repair technique to two techniques currently being used; drilling of crack-stop holes and attachment of steel splice plates. The intention of this research was to test the use of CFRP as a repair technique and validate its use for further testing more applicable to actual field conditions. This thesis is organized into two primary parts. The first, entitled "Use of CFRP Overlays to Repair Fatigue Damage in Steel Plates under Tension Loading" details the experimental testing on component specimens. The second, entitled "Evaluation of Fatigue Damage Repair Measures in Welded Steel Plate Bridge Girders" details the analytical evaluation of different repair techniques and loading conditions. Procedural appendices have also been included to aid in future research in involving the testing of CFRP overlays. These appendices include the manufacture and attachment procedures of CFRP developed at the University of Kansas, an operational manual of sorts for the two testing machines used to complete Part 1 of this study, and the manufacture and attachment procedure of clamps used to control de-bonding of the CFRP overlays.