Building W-Shapes from Plate

[uwmadd]

I have a situation to which I have lack experience and kindly request some discussion.

We have a structure that uses approximately 10,000 feet of 175mm deep I beam (H175x175x7.5 – A Chinese shape). The Chinese fabricator is asking to build up all of the sections from plate material (apparently a sourcing problem for hot-rolled shapes). The welding of the flanges to the webs will be done with continuous fillet welds, however, a penetration weld is NOT to be performed through the web (fabricator is worried about warping). I have my doubts regarding the quality control and NDE that will be performed on the welds. I have been told that building beam profiles is common in this region. As the structure was designed using hot rolled shapes, I have some obvious concern over whether built-up beams from plate will be sufficient or not. Without significant experience with this sort of situation, I thought I would post.

The structure could be re-designed using Plate Girder techniques, but am hoping to minimize re-work. I have concern over the level of residual stress introduced into the structural shapes due to their small profiles. Additionally, manufacturing the exact geometry of the hot rolled profiles would be very difficult when considering the radius between the web and the flanges.

Surely, this subject has come up before but my searching on the forum has not yielded much success. Thank you in advance for any discussion you may be able to offer.

 

[plasgears]

Reminds me of the type of built-up beam with hexagon cut outs that is fabricated by cutting a shorter beam. The cut line is along two parallel lines on the web. The pattern is offset trapezoids. After the cut, the two pieces are realigned for maximum beam height, and the weld is an interrupted weld at the neutral axis.

I personally would opt for a built-up box beam for section stability.

 

[HgTX]

"We engineers in the USA don't have to worry about the quality of a beam. That is the supplier's responsibility."

We engineers in the USA in the QA field have to worry about making sure the suppliers are actually meeting their responsibility. (We do a better job of this with the fabricators than with the mills, who seem to be answerable to no one at all...)

Hg

Eng-Tips policies: faq731-376

 

[pba]

In UK and European codes, there is a reduced compressive stress for fabricated sections as opposed to hot rolled. I don't know if that applies to US codes...