Welding steel joists

By SWN1158 (***)

Date 07-11-2019 13:58 Edited 07-11-2019 14:01

The structural welding code, with regard to the preparation of base metal, states that "a thin rust inhibitive coating may remain", but obviously, it cannot compromise the quality of the weld.

By 803056

Date 07-11-2019 20:04

Welcome to the Farm Code.

I'm not defending practice, but consider the loads on the weld securing the joist tail to the top flange of the steel frame. The weld simply keeps the joist from moving left or right during erection. Once the decking and roofing materials are in place, that joist "ain't going nowhere!"

The load on the joist tail is the total gravity load due to the roof structure and snow or rain. There are no forces to speak of in the lateral direction unless the structural steel frame is pitched (more than a slight pitch for drainage). If the pitch of the structural framing is sufficient, additional bridging and additional weld will likely be specified by the designer. If the structure is located in a seismic active region, there will be additional requirements listed by the drawings regarding how the joists are secured to the framing, how the lower chords are secured, and additional bridging requirements.

As an inspector, it is easy to look at a welded joist tail and nit-pick it to death. I would be more concerned with the factory welds that are not inspected. About the only discontinuity prohibited is a shop weld that is broken.

Just saying.

Al

By ironworker1 Date 07-12-2019 12:15

Thanks for the information.

Can you tell me the code and section that the statement "a thin rust inhibitive coating may remain" comes from? It would be very helpful.

Thanks!

By Jim Hughes (***)

Date 07-12-2019 13:28

AWS D1.1. 5.14.1, 5.14.4.1, commentary C-5.14.1, 5.14.4.

By SWN1158 (***)

Date 07-15-2019 12:00

ironworker1,

The reference I initially made... "a thin rust-inhibitive coating, or antispatter compound may remain" referenced D1.1 2010 @ 5.15 Preparation of Base Metal. There is no such reference, verbatim, in the 2015 edition. In the Summary of Changes, it states "5.14.1–5.14.4 (Previously 5.15) Substrate cleanliness requirements were significantly revised." Preparation of Base Metal is now part of 5.14, as Jim has referenced. Paragraph 5.14.4.2 applies directly to your question:

5.14.4.2 Welds are permitted to be made on surfaces with surface protective coatings or anti-spatter compounds, except those that are prohibited in 5.14.4.1, provided the quality requirements of this code can be met.