Loss of Capacity Due To Welded Aluminum In Railings – Signs – Structures

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Regarding any aluminum railing project, it is imperative to understand the life-safety issue that arises when welding an aluminum railing or sign post.

For example, a rail is classified as a life-saving fall guard for any elevation above 31 inches above grade. The aluminum alloys normally used (such as 6061-T6) get their strength from a heat-treatment process. Welding weakens the heat-treated aluminum in the vicinity of the weld, called the heat-affected zone (HAZ), reducing the strength by approximately 40 percent.

Weld_failureAny aluminum specifier or designer must account for the weakened state of the welded members. According to “Specification for Aluminum Structures,” published by The Aluminum Association, if a weld is located within 1 inch of any connection, the designer must analyze the connection with appropriate strength reduction. In general, this means that welds placed within a given distance of the base of a small aluminum rail post will cause the post to fail when the code-required 200-lb load is applied at the top.

It is important to note, however, that the highest load force (due to bending on a railing or wind on a sign) usually occurs at the lower portion of the post. Thus, welded connections at the top of the railing or sign post are usually strong enough to sustain the code-required loading.

We offer the following suggested alternatives when welding a post at the base which must be checked on a case-by-case basis:

  • Increase the size and thickness of the railing post
  • Provide structural adhesive (e.g. Lord Engineered Adhesives) for the connection as opposed to or in addition to welding components
  • Provide structural insert within post (also connected to the base by welding or fasteners)
  • Weld pickets to their own ‘box frame’, then mechanically attach frame to posts
  • Utilize mechanical connections and do not place any weld within 2′-6″ of bottom of post
  • Use an external bracket to further support the post (like a ‘kickstand’ or exterior scroll)

Please feel free to contact us with any questions or to review your site specific project need.


Last Update: December 15, 2022  

March 15, 2021  Codes & Standards, Engineering  
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