Splicing Rectangular Tubes 1

[SmithJ]

Hello All,

We are working on a project where we have Rectangular HSS Tubes that are subjected to large tensile and compressive forces and some minor bending. In order to limit drop, we are considering splicing our tubes and maximizing use of our material. Does anyone have any recommendations on this issue?

The AWS D1.1 allows for groove welding if a proper backing plate is used. However, I have heard a number of experts mention that using a backing plate compromises the weld because the backing plate becomes part of the overall weld and provides a weak point for stress concentrations and eventual weld failure.

I do not really understand the implications of splicing tubes in this manner and would appreciate any comments or advice that is out there. It would be great to hear from building and welding inspectors about what they look for in such spliced connections.

Thank you in advance for your time.

JS.

 

[structuresguy]

Well, there are several different welds which are pre-approved by AISC for making a butt splice. Some require backing, others do not. Depends on a few factors, such as weld process and material thickness.

First, and most important question, do you need to develop the full capacity of the section at the splice? If not, use a partial penetration weld. No need for backing then at all.

As for worrying about the backing causing stress problems in the weld, is the part under fatigue loading? You say both tension and compression, but is it highly repetitive reversed cycle loading? If not, I would not worry about stress concentrations under normally static style loading.

I have not given you any specific info, so I realize this post may not be of much use to you. Maybe if you posted a bit more detail regarding the members spliced and type of loading, the community would be better able to help you out.

Good luck.

 

[am]

I recommend you to consult the following book.

DESIGN GUIDE FOR HOLLOW STRUCTURAL SECTION CONNECTIONS by j.a. packer and j.e. henderson;

This has been published by Canadian Institute of Steel Construction
ISBN 0-88811-076-6

Regards

AM