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FSS operator adjusts flange butt-welding jig for Arcmatic electroslag equipment. The NG-ESW technique can cut flange butt-weld time by two-thirds.
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Several of the steel girder bridges for the Courtney Campbell Causeway interchange near the Tampa airport have flanges butt-welded by the new electroslag.
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TAMPA, FL — Florida Structural Steel (FSS) in Tampa sees significant economic advantages in splicing bridge girder flanges with the new Narrow-Gap Electroslag Welding (NG-ESW) technique. Currently, this company is the only fabricator in the country using NG-ESW for bridge work. According to Dale Ison, Manufacturing Manager, the technique cuts welding time for butt-splices of top and bottom flanges by about two-thirds.
The Federal Highway Administration (FHWA) approved the use of NG-ESW in March of 2000, rescinding a moratorium imposed in 1977. The technique applies to bridge steel members that are in tension, reversal, or compression, but not fracture-critical steel members or those in geographic zone 3.
Only Texas and Florida have allowed this welding technique for splicing of main members in their bridges. Other states are waiting for NG-ESW to appear in the printed AWS codebook for bridge welding. Besides Florida Structural Steel, Ison knows of only one other bridge fabricator in Texas that earlier used electroslag welding on two girder bridges, but then left the bridge fabrication business.
"The American Welding Society will include NG-ESW in the D1.508 code, but the book won't be published for another year or so," says Ison. "At that time more state DOTs will undoubtedly approve the technique.
"FDOT wrote it into their new specifications for Section 460 Structural Steel and Miscellaneous Metals," says Ison. "Florida Structural Steel is working on ten girder bridges for the Courtney Campbell Causeway interchange, in the vicinity of Tampa International Airport. "This project," he says, "falls under the 460 specifications, so FSS applied to FDOT for, and received, permission to use NG-ESW to butt-splice girder flanges. This interchange project involves ten girder bridges and about 1,400 flange butt-splices.
"Unfortunately," says Ison, "we did not qualify for NG-ESW in time to use it on all ten girder bridges in the project. FSS will probably use it on six bridges, portions of which have already been erected. If we had been able to weld all the flange splices with NG-ESW," he says, "the equipment would have paid for itself on this project alone." Ison notes that the electroslag equipment came from Arcmatic Corporation (Vallejo, CA) at a cost of about $125,000 plus $60,000 for the flange welding jig.
All the electroslag bridge welds made by Florida Structural Steel undergo 100 percent ultrasonic and X-ray inspection, as required by the code. "KTA-Tator, Inc. (Pittsburgh, PA) is witnessing the inspections for us," he notes.
As an example of the man-hours saved, Ison estimates the total time for splicing two-inch thick plates, 24 inches wide, would take about 22 hours by conventional welding. A comparable electroslag weld would be ready for testing in about six to seven hours.
Although Florida Structural Steel is the only bridge fabricator now using electroslag welding, the process is relatively common for use in structural steel for buildings. “I know a number of building fabricators who have been applying it for various uses in buildings for years,” Ison says.
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