Effects of Realistic Heat-Straightening Repair on Damaged Steel Beams

Abstract

Realistic implementation of heat straightening in the field can include imperfections such as temperatures much higher or lower than recommended values, overstraining, mechanical hot bending, and multiple heat straightening. Experimental investigations were performed to evaluate the effects of realistic heat straightening with imperfections on damaged steel beams. Six steel beam specimens were fabricated from A36 steel plates and tested to evaluate the effects of various damage and repair parameters on realistic heat-straightening repair. Test specimens were statically damaged by using a hydraulic actuator, and heat-straightening repaired by applying Vee heats and restraining forces in the plastically deformed region. The damage and repair parameters considered in the test were damage magnitude, restraining force, maximum heating temperature, and number of multiple damage–repair cycles. The material properties, including the structural properties, and the fracture toughness of the damaged–repaired beam specimens were determined and evaluated. Specimens subjected to overheating (up to 1,400°F) during repair and those subjected to heating up to 1,200°F had similar structural properties and fracture toughness values after repair. Specimens subjected to one or three damage–repair cycles had similar structural properties and fracture toughness. However, specimens subjected to mechanical hot bending [i.e., heat-straightening repair with underheating (temperature less than 1,000°F and excessive restraining force over 50% of the plastic moment capacity of the section)] had poor fracture toughness values.

Effects of Imperfections in Heat Straightening Repair of Steel Beam Bridges

“…Experimental investigations were conducted to evaluate the effects of damage followed by realistic heat straightening repair (with imperfections) on the material properties and serviceability of large-scale steel beam bridges. The test bridge was constructed following an analysis of an Indiana Department of Transport database developed during previous research ( 1 , 2 ). The analysis indicated that: (i) A36 was the most frequently damaged-repaired steel type, (ii) composite continuous bridges were the most frequently damaged-repaired structure type, and (iii) considering elastic rebound of the damaged steel, 30 times the yield strain (ε y ) was typically the maximum average damage amount.…”

“…In previous research ( 2 ), the most detrimental deviations commonly found in field applications of heat straightening were: (a) underheating below 1200°F (about 800°F), (b) overheating above 1200°F (about 1400°F), (c) overstraining above the recommended restraining force limit, and (d) multiple heat straightening of the same beam more than two times.…”

“…The primary focus of prior research on heat straightening repair has been on: (i) developing effective heating patterns and techniques, (ii) determining thermo-plastic deformations, (iii) determining the structural properties of steels after heat straightening, and (iv) developing guidelines implementing the heat straightening repair process. It is important to note that most prior research has not included the effects of imperfections in the heat straightening repair process other than Sohn and Varma (1,2). have conducted detailed experimental investigations to evaluate the effects of multiple damage-heat straightening repair cycles on the structural properties, fracture toughness, and microstructure of A36, A588, and A7 bridge steels.…”

“…Sohn and Varma ( 1 , 2 ) have determined the effects of realistic imperfections including multiple damage–heat straightening repair cycles, overheating, underheating, large damage, and overstraining and their combinations on the structural properties, fracture toughness, and microstructure of A36 bridge steel beams. In summary, the major findings were that multiple damage-repair cycles (up to three times) and overheating (temperatures up to 1400°F) could be acceptable imperfections in heat straightening repair.…”

“…Heat straightening is one of the most effective and efficient methods to repair the damage (permanent deformations) caused by over-height vehicle impacts. An evaluation of the Indiana heat straightening repair database indicated that the most frequently damaged-repaired bridges in Indiana were made of A36 steel ( 1 , 2 ).…”