Welding of Steel Structures in Service Conditions(Mechanics, Strength & Structural Design)

概要

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To describe the displacement behavior of the weld joint of a bridge in service, Δδ (the root gap opening displacement) and Δδ_v (vertical displacement) are measured at the weld joint. Δδ in service is observed as the displacement caused by the amplitude of the vibration arising from the passage of a motor vehicle and the static deflection because of the weight of the vehicle. The static deflection due to of the weight of the vehicle is the major part of the observed displacement. In the general, the frequency of Δδ lies between 0.2〜0.3(Hz) and 4〜7(Hz) and the maximum amplitude is 1(mm). There are basically two methods based on Δδ for the prevention of hot cracks in service repairs. One is to lower Δδ itself by attaching the restraint plates to increase the mechanical restraint of the weld joint. The other is to make Δδ_<cr> large, which is the material properties. In order that Δδ_<cr> could be made large, weld cracking tests were carried out for the covered electrodes D4316 and D5816 much used in the repair work on the bridges and for the newly developed electrode D5016-MOD. Δδ_<cr> for D5016-MOD was 3〜4 times larger compared with Δδ_<cr> of D4316 and D5816. By using D5016-MOD, the welding conditions in service can be largely relaxed. Successful welding in service conditions has been demonstrated through actual repair work.
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