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How Good Is Your Weld?
by Wayne Thompson, P.E., LEED AP
At CTL Thompson, I wear many hats, but there is one that I’ve worn for more years than any other. I’m a design engineer. Thousands of plans have gone out the door with my P.E. stamp on them, signifying that I am attesting that the structure built per my plans will stand up to design loads, thus protecting the public health and welfare. In other words, it won’t fail.
Like any other engineer, I have equations, codes, and checklists to ensure that I design a structure so it won’t fail. Beyond that, I now have years of experience to enable me to step back, look at a specific structure and say – “How is it going to fail?”.
In the helical pile industry, you should be asking yourself the same question. How will the pile fail? Most of you will probably say - the weld. Just like any other structural system, connections are the critical path. For a helical pile, I am most concerned with the welded connections (plate to shaft; coupler to shaft). To their credit, I have yet to meet a manufacturer who doesn’t realize this critical component. But I’ve also met several people at various levels of the industry who say, “If the pile is going to fail, it’s going to fail during installation.” For the most part, I agree with that theory. But I still have a problem with it. The following example illustrates this:
It’s day one of foundation construction for a project I just designed. CTL’s field inspector calls and says that they are having problems with helical installation. One of the (40) helical piles on the project failed during installation. The helix bearing plate sheared off from the shaft near the specified design torque. The other (39) piles reached the specified design torque at the desired depth. The manufacturer can supply a replacement pile to the site within four working days. So, what are the ramifications of this failure?
1. I likely approved the product submittal for the helical piles. Right now the owner is questioning my judgement.
2. There is a fairly significant negotiation happening as to who pays for the lost days of production, the potential for liquidated damages, any equipment rental or any re-mobilization.
3. A revised load testing program for the installed piles has been generated. The owner has demanded 100% of the piles be tested. The owner reluctantly agrees to pay a discounted fee for the load tests but is expecting us to observe the tests for free.
4. Long-term, I’m probably done with the helical manufacturer, and I will be very picky about the next manufacturer I choose.
Those four items are being pondered by the foundation subcontractor, the GC, and the owner, in addition to anyone else to whom we tell the story. So - how good is your weld?
Wayne Thompson, PE, LEED AP
CTL | THOMPSON, INC
400 North Link Lane
Cell: (720) 347-0054