Contractor Designed Elements 7

[EDub24]

Hi, I've got a general question. Typically I push some items that require design onto the Contractor (guardrails, metal stairs, pipe supports etc). They usually have an in-house Engineer design/stamp the items or they sub out to another engineering firm. My question is how in-depth of a review do you typically do when the Contractor submits the design? Where I work I've seen 3 trains of thought.

1) It's the Contractor's design/stamp so they are only submitting for the record so no review is done.
2) A thorough in-depth review where everything is looked at and verified/checked.
3) A cursory review where the design criteria, design procedure and some select structural items are looked at.

Typically I do #3 and perform a cursory review unless the designed element is pretty major in which case I'll do a more thorough review although in both cases I'll word my comments as suggestions/requests to verify or check rather than direct them to do something. Thanks!

 

[TehMightyEngineer]

This sounds like a race to the bottom. Whichever supplier can provide the lightest design wins the project as long as they can provide some calculations covering his numbers.

Well, theoretically they can't go any lower than either the specification or the local building codes allows. Plus the EOR can always raise minimum design requirements if they have justification for it.

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[MrHershey]

I don't understand. Are they redesigning it to use lighter sections? Or are they replicating your design? If they're not saving him money, I don't see what the advantage is for the contractor. I've got light gage metal submittals that seemed like they used gages that you could see through. And those were cases where I provided a design.
This sounds like a race to the bottom. Whichever supplier can provide the lightest design wins the project as long as they can provide some calculations covering his numbers.

A lot of times it's same or similar. Sometimes they'll go a little lighter or they'll trade thickness for spacing or they'll swap things in based on their current local availability. Often it's not so much section sizes but connectors. Our office typically will use either generic clips and connectors or Simpson but allow for equivalent to be used. So a lot of times subs will gather multiple prices on the supply side and whoever wins will re-engineer things using *their* hardware and submit calcs for it (I'm told usually for free). Usually they'll include calcs for sections too even if they're not changing anything there, just do the whole package instead of bits and pieces.

 

[EDub24]

Sorry for the delay - had to fly out of town for a committee meeting and am just now getting back to this thread. A lot of great information has been posted that I need to digest. Sounds like a lot of people lean toward #3 and possibly #2 depending on what is being designed.

 

[JLNJ]

We had a case recently where the designer, despite being registered in the State and dutifully affixing his seal to the calculations, was simply not competent.

We had many conversations in house about where our obligations lie.

The Architect, 'Don't worry, we'll delegate the complete design, you won't have any time into it but a quick review." Ha! I had more hours in "review" than if I would have designed it myself.
The Contractor said, "What do you care, it has his seal on it." Ugh.
Another engineer, in house, "Should be report this guy to the engineering board?" Good question. Hard to answer. I decided not to.

After many rejected submittals and a few tense phone calls, the contractor was convinced to find a different engineer to take up the task. What a mess.

 

[dik]

I check shop drawings because its often the last kick at the cat to locate an error.

Dik

 

[BridgeSmith]

About 3 years in as a DOT bridge designer, I'm on the phone with the engineer whose stamp is on the design calcs for some prestressed girders, attempting to question whether we had properly conveyed the loading requirements (our analysis showed the concrete tension was too high), when he says "just tell us how many strands to put in and we'll do it". As diplomatically as I could muster, I responded that it was his design and I also wasn't qualified to do the design. I was an EIT with no prestressed experience (we always let precasters design). What I didn't mention is that it was also not my job; that's what we were paying him for. I covet my license far to much to ever offer to do let someone else decide that on something I was putting my stamp on.

 

[dik]

You get less sensitive as you age... I'd just circle the calc area, and, add a note to please review.

Dik

 

[BridgeSmith]

I wasn't really sensitive about it. I was just shocked at the lack of concern he showed regarding his design, that he was willing to put it in my hands, having no idea what my qualifications were.

Perhaps it would have been best to just mark up the design and send it back, but I was inexperienced and they were in a hurry to get approval, so I called hoping we could figure out the discrepancy. I assumed either he would say "oh, I didn't realize you're designing for an HS25 truck and 3" of asphalt" or he would explain where I screwed up.

 

[Settingsun]

HotRod10, it sounds as though you were suggesting the girders needed to be strengthened. If the designer was already happy with them, then there wouldn't be an issue with the stronger girders (provided they don't explode upon transfer). You say time was of the essence so it may have been the case that two extra strands today cost less than the original design next week.

Designers don't know what type of reviewer they're dealing with on first contact. Some reviewers will indeed dictate their version of the right design and reject even minor differences. In those cases, the options are to match the reviewer's requirements or dig in for a protracted argument. The latter often results in having to go over the reviewer's head within the roads authority.

 

[BridgeSmith]

Steve, I stated to him clearly that I was not questioning his design, only whether we had properly conveyed what the loading would be. I suppose he may have still felt I was "getting in his business", which was not at all my intent. It's also possible that his response was meant to convey only that he would add strands if we wanted more. However, that could result in exceeding the tension in the top of the beam at release, so design parameters could be violated there as well.

 

[BUGGAR]

When I look at someone's work that is based on my input to begin with, I don't look for his mistakes, but for mine.

 

[dik]

Buggar... great comment.

Dik