Fundamental Concepts of Heat-Straightening Repair for Damaged Steel Bridges

Avent, R. Richard; Mukai, David

doi:10.3141/1680-08

Cited by 3 publications

(8 citation statements)

References 5 publications

(5 reference statements)

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“…It has been shown by Avent, Fadous, and Boudreaux (1991), Mukai (1998), andRoeder (1986), that the amount of movement during heat straightening of damaged flexural members is directly proportional to heating temperature up to at least 870°C (1800°F). Permanent movement can occur with heating temperatures as low as 370°C (700°F).…”

Section: What Temperature Limits Are Necessary When Heat Straightening?mentioning

confidence: 99%

“…There are several basic types of heats that are frequently used as illustrated by Avent et al (1991), Avent and Mukai (1998), Ciesicki and Bulter (1968), and Holt (1955, 1965, 1971, 1977. For some applications only one type is required.…”

Section: What Are the Basic Types Of Heats?mentioning

confidence: 99%

“…Of more significance are the properties of damaged plates (or rolled shapes) after experiencing the large number of heats required to fully straighten the member. Avent, Robinson, Madan, and Shenoy (1993a), Avent and Mukai (1998) conducted tests on seven plates and four beams which were damaged to strain ratios ranging from 30 to 100 and then heat straightened. In general, it was found that the yield stress in the heated regions increased approximately 10 percent over that of the unheated member.…”

Section: What Is the Impact Of Heat Straightening Repair On Yield Str...mentioning

confidence: 99%

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What You Should Know About Heat Straightening Repair of Damaged Steel

Avent,

Mukai

2001

Eng J

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The repair of damaged steel through the application of heat has long been considered an art rather than a science. As such both the methodology and results have varied considerably from one practitioner to another. Because steel tends to be a forgiving material, successful repairs outnumber failures. Yet material properties may be compromised resulting in a weakened in-place structure. In addition, it is not unusual for a fracture to occur during the repair process. As a result, the use of heat straightening (or flame straightening) has had limited application. Many engineers are reluctant to allow heat straightening because of the lack of an established method of application as well as the lack of quantification of steel properties after the repair is complete. The purpose of this paper is to provide some engineering guidelines for use of the heat-straightening process.

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Section: What Temperature Limits Are Necessary When Heat Straightening?mentioning

confidence: 99%

Section: What Are the Basic Types Of Heats?mentioning

confidence: 99%

Section: What Is the Impact Of Heat Straightening Repair On Yield Str...mentioning

confidence: 99%

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What You Should Know About Heat Straightening Repair of Damaged Steel

Avent,

Mukai

2001

Eng J

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“…The combination of restraining force and heating produces thermo-plastic strains and deformations that are opposite to the permanent damage deformations. Several repetitions of the combined restraining force and heating are required to reverse (repair) the permanent deformations to acceptable levels within tolerance ( 3 – 5 ).…”

mentioning

confidence: 99%

Effects of Imperfections in Heat Straightening Repair of Steel Beam Bridges

Sohn

Varma

Connor

2018

Transportation Research Record

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A 40 ft. long two-span continuous steel bridge with two composite beams was constructed in the laboratory and subjected to damage followed by heat straightening repair. A36 steel section (W30 × 90) was used for the main girders (beams). Four spans (specimens) of the test bridge were statically damaged at each midspan using a hydraulic actuator, and subsequently repaired by applying Vee heats and restraining forces in the damaged region. Restraining force magnitude (corresponding to 0.4 Mp: 6.2 kips and 0.6 Mp: 9.5 kips), maximum heating temperature (800°F, 1200°F, and 1400°F), and the number of multiple damage-repair cycles (one and three cycles) were considered as the test parameters. The steel material properties were measured by taking samples from the repaired areas, and compared with undamaged steel material properties. Samples taken from specimens subjected to overheating (up to 1400°F) had similar structural properties and fracture toughness values as those taken from specimens subjected to normal heating (up to 1200°F). Specimens repaired with overstraining (0.6 Mp) combined with underheating (up to 800°F) required the largest number of heating cycles to fully repair the same damage. The fracture toughness of samples taken from specimens subjected to multiple (three times) damage-repair cycles was lower (decreased to about 84%) than the fracture toughness of samples taken from specimens subjected to only one damage-repair cycle. Therefore, multiple heat straightening repairs of a damaged beam should be performed with caution. With reference to serviceability performance for AASHTO HL-93 live load, the midspan deflections of beam specimens subjected to damage and heat straightening repair were comparable to those of undamaged beam specimens.

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“…Two methods are used: (1) heat straightening and (2) cold straightening. In heat straightening, localized heat is applied in accordance with established procedures (Avent and Mukai, 2001). In cold straightening, rectification is achieved by applying loads.…”

mentioning

confidence: 99%

Fabrication Aids for Cold Straightening I-Girders

Gergess,

Sen

2004

Eng J

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Fabrication out-of-straightness in steel girders can be rectified using heat straightening or cold straightening. While heat straightening has been extensively researched, little information is available on cold straightening where loads are used to achieve the same result. This paper provides an analytical framework for an innovative cold straightening (also referred to as cold bending) system developed by a fabricator. Maximum safe limits on loads, out-of-straightness and load frame configurations that are consistent with prevailing "Load and Resistance Factor Design" (LFRD) criteria are proposed. Fabrication aids for Grade 250 (Fy = 36 ksi) and 345 (Fy = 50 ksi) steel are developed and their application illustrated by three numerical examples.

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Fundamental Concepts of Heat-Straightening Repair for Damaged Steel Bridges

Cited by 3 publications

References 5 publications

What You Should Know About Heat Straightening Repair of Damaged Steel

What You Should Know About Heat Straightening Repair of Damaged Steel

Effects of Imperfections in Heat Straightening Repair of Steel Beam Bridges

Fabrication Aids for Cold Straightening I-Girders

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