Heat-Straightening Repair of Damaged Steel Bridge Girders: Fatigue and Fracture Performance
ATLSS Engineering Research Center -- Lehigh University
Dr. Robert J. Connor (Purdue University)
The project final report is available as NCHRP Report 604.
For many years, heat-straightening of damaged steel bridge girders has been more an art than a science. As a result, its use as a repair technique has been limited by concerns about its effects on the properties of the steel. Even with this limited use, heat-straightening has often proven to be an effective repair procedure.
Recent research has better quantified heat-straightening in engineering terms. Key factors such as heating temperatures and patterns required for specific damage configurations as well as methods for calculating degree of damage and for predicting movement during heat-straightening are now better defined. Less certain, however, are the fracture and fatigue performance of heat-straightened steel compared to undamaged steel and the degree to which the damage and heat-straightening history of the steel affect that performance. These questions have been prompted by situations in which field-repaired beams subsequently fractured.
This project will evaluate the fatigue and fracture performance of heat-straightened steel to better understand issues such as the engineering properties of repaired materials and the limits on the degree of damage reparable by heat-straightening. An upcoming pooled-fund project to be undertaken by Louisiana DOTD and the Federal Highway Administration will develop criteria for the field use of heat-straightening considering the degree of damage and the required jacking forces as well as the application of this repair process to high-performance steels. The complementary work of these two projects will promote more rational use of heat-straightening for bridge steel repair.
The objectives of this study were to (1) determine the relative effects of damage and subsequent heat-straightening on the fatigue and fracture performance of steel girders; (2) identify and quantify the material and process parameters that may affect the fatigue and fracture performance of heat-straightened steel girders; and (3) establish guidelines, including limits on initial damage and critical process parameters, to minimize the potential for fracture and fatigue problems in heat-straightened steel girders.
Product Availability: The project final report is available as NCHRP Report 604: Heat-Straightening Repair of DamagedSteelBridge Girders: Fatigue and Fracture Performance.