Extending Bridge Service Life Through Field Welded Repairs and Retrofits (2016) / Chapter Skim
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Pages 7-17
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From page 7... ...
8 improvement, capacity strengthening, and corrosion and impact damage repairs or retrofits. Fatigue Improvement This typically includes retrofit of out-of-plane and distortioninduced cracking by welding the connection stiffener to the flange.
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9 fatigue-sensitive detail in a primary load carrying member. Therefore, this method is often the last choice when other repair methods are not effective at stopping crack growth (Zhao and Roddis 2004; Hu et al.
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10 Field welded repairs and retrofits will likely involve the welding of types of steels where the ASTM specifications are out of date compared with current specified bridge steels; therefore, the current welding codes may not account for special requirements of these steels. When the composition of the steel is unknown or in doubt, it is necessary that analysis be performed so that a welding engineer can determine whether it is suitable for welding.
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11 qualified welding operators, written and qualified welding procedures, and workmanship requirements. AWS Structural Welding Code D1.1:2010, Section 8, on the other hand, includes additional requirements and guidance for field welding on existing structures.
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12 It was also found that many of the state agencies had field welding inspection guides that included information to aid weld inspectors. This includes, but is not limited to, information on the typical weld symbols, welding procedures, electrodes and electrode storage, preheat and interpass temperatures, weld joint preparation and cleaning, weld inspections, equipment, and typical weld discontinuities.
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13 This does not imply that the quality or quality control requirements are different for field welds than for shop welding. It simply means that it can be more difficult to maintain quality control under field conditions.
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14 be slightly more sensitive to tightly closed cracks; however, it can be more time consuming and requires more skill to differentiate actual discontinuities from false calls. MT can be affected by wind.
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15 in the immediate vicinity around the weld. It is suggested by Miller (1993)
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16 and rewelding technique required a high degree of skill and inspection and, therefore, expense. This type of repair restored the cracked location to its uncracked state; however, without an additional retrofit to lower or eliminate the out-of-plane stresses in this region, the crack would likely reappear.
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From page 16... ...
17 about micro-cracking in the HAZ during solidification when welding under live loading, a decision was made to stop traffic during the welding operation for the trial retrofits. Slight undercutting was noted in the top flange weld toe and debris between the stiffener and the top flange caused impurities in the root pass.
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From page 17... ...
18 maintain under field conditions; however, the quality requirements are the same for field welds as shop welds. Research on field welding has been performed using experimental testing of fatigue crack weld repair while under tensile stress or dynamic loading.
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