Electric Forging Weld Capacity - Open Web Steel Joist 1

[iceberg187]

Has anyone run across electric forging welds before?

We are looking at an existing open web steel joist that was fabricated in 1942 by Truscon Steel Company. The bottom chord is a tapered T shape, the top chord is a channel shaped like a W, the web members is a continuous bent rod.

The weld between the bent rod web diagonal members and the joist top and bottom chords appears to have been provided by means of "electric forging" per the Carnegie Pocket Companion 1934 p. 386 listed on SlideRuleEra's site. Also attached is a field photo of this weld connection.

Does anyone know of any resources or have any other information regarding this "electric forging" weld type or capacities?

Through analysis, we have determined that the existing joist members are adequate for the snow drift load that will be added to these joists. The welds are currently the weak link since we have no allowable design capacities for this weld type. There are hundreds of these joists that are affected by this condition, so we are trying to do everything we can to determine the existing joist design capacity.

Thanks in advance for any assistance that you might be able to offer.

 

[Ron]

Forge welding is when the materials are heated to almost the melting point and then "hammered" together by whatever means (that could include jamming them together hydraulically). It can produce a strong weld, but is somewhat susceptible to lack of fusion issues.

Nondestructive testing is difficult on these welds due to the laps and geometry.

I would suggest that you load test and check deflection response if you are concerned about capacity.

Check with the James Lincoln Foundation for publications and info on forge welding. I'm sure there are plenty of internet sources as well.

 

[iceberg187]

Ron, thanks for the information.

The James Lincoln Foundation referred us to AWS D1.7 - Guide for Strengthening and Repairing Existing Structures. However from what we have been able to locate of this document, it appears D1.7 is intended for evaluation of existing welds with flaws, discontinuities, undersized, damaged etc. relative to the specified weld. It does not appear to provide design capacities for the specified weld itself.

The James Lincoln Foundation also mentioned some concerns about the uncertainty of the weld due to the uncontrolled carbon content of A7 steel. Even with steel chemical composition testing, they were reluctant to provide design capacities due to the uncertainty of the weld type.

We also contacted SJI and AWS, but they did not have any information regarding forge welding capacities. There is information available on the internet regarding the forge welding process (the AWS Design Handbook also has information), but we were not able to locate information regarding weld design capacities.

We were trying to avoid destructive testing, but it appears that may be the only feasible option.

Thanks for the input.