Everyone Says the Structure is Overdesigned
Everyone Says the Structure is Overdesigned
(OP)
So the common theme in today's construction/engineering industry is for the contractor to tell the owner or architect that the structural engineer has over designed the building and is just being conservative. This happens a lot whether you are designing it per code or adding in some conservatism. So how does your firm address these concerns?
Just recently in my area I have had the good fortune of adding additional clientele due to their previous E.O.R. getting so frustrated with the GC that they told them off. Obviously, the GC did not take too kindly to this and so are using my firm for their business instead. My approach when the "over designed" discussion takes place is to try to discuss new implementations of the codes and the loadings. This usually alleviates some of the tension and allows everyone to get back on the same page.
So how does your firm do it?
Just recently in my area I have had the good fortune of adding additional clientele due to their previous E.O.R. getting so frustrated with the GC that they told them off. Obviously, the GC did not take too kindly to this and so are using my firm for their business instead. My approach when the "over designed" discussion takes place is to try to discuss new implementations of the codes and the loadings. This usually alleviates some of the tension and allows everyone to get back on the same page.
So how does your firm do it?






RE: Everyone Says the Structure is Overdesigned
Designing according to code is the MINIMUM design. For most structures and occupancies, the loading and design elements required by code will be conservative (typically by 40% at full design load, and then few structures see the full design loads), but the code is why we have seen very few structural failures in the US. Just look at the collapse today in Bangladesh for an example of construction that was probably "almost adequate" for quite a long time.
I have met engineers that design on the cusp of code compliance because of what I call "fear of future VE" - they cut every corner to reduce what might be perceived as over-design. The result I saw while doing forensic structural work was serviceability problems that resulted from failing to consider everything in the cost cutting.
The thing that I am hearing from larger contractors is that engineers need to simplify designs for constructibility, rather than trying to save every pound of material. Save the complexity for the places that require it. Reduce the number of beam and column marks, making repetitive things as uniform as possible (don't make them similar when they can be the same.)
And ultimately, we have the education, experience, and licenses to do engineering. It is our responsibility to properly apply the code and design the proper structure.
RE: Everyone Says the Structure is Overdesigned
I can give you two of the three: Reduced engineering cost, reduced schedule, or reduced construction cost.
RE: Everyone Says the Structure is Overdesigned
RE: Everyone Says the Structure is Overdesigned
If it's just idle complaining, I'll generally start babbling on about one tricky part of the design. Seismic is great for it. Everyone knows seismic provisions are the current target of a lot of code development, plus a lot of people don't understand it. So if you start going on about ductile moment frames and R values and how you've avoided detailing requirements to simplify construction and things like that they'll run out of things to say.
RE: Everyone Says the Structure is Overdesigned
RE: Everyone Says the Structure is Overdesigned
If you are confident that your design is good you should be able to explain design decisions to the contractor and they should back down.
I expect questions on a design-build contract. A good GC will accept a good explanation and not press you to push the rules. The last one I worked with was good. They confronted me about many design changes and cost savings. In some cases they were correct and the additional cost was unwarranted. In most cases no savings could reasonably be realized. As long as I had a good argument they dropped it. If I didn't have a good argument I'm wrong anyway.
If you are working with a contractor who will back down when presented with evidence and reason, good. If not, you need to stop working with that client. They will stab you in the back when it becomes expedient because they are fundamentally dishonest.
RE: Everyone Says the Structure is Overdesigned
RE: Everyone Says the Structure is Overdesigned
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
RE: Everyone Says the Structure is Overdesigned
It's funny that those contractor's who are quick to condem designs are the ones who say "we're just contractors, not Engineers" when something goes wrong.
The wiser, more experienced contractors don't go down that road and stick to their part of the process; constructing.
RE: Everyone Says the Structure is Overdesigned
Perhaps you saw it in response to one of the photos I posted in Pat's pub.
thread1088-343440: Precision Engineering
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JHG
RE: Everyone Says the Structure is Overdesigned
RE: Everyone Says the Structure is Overdesigned
This is akin to the pursuit of Adequacy. The problem is that if the structure had no problems it must have been overdesigned compared with the adequacy target, so we must design tighter next time.. ..and on until a structure tells us that we have gone too far.
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
RE: Everyone Says the Structure is Overdesigned
These comments about our structures being over designed probably has less to do with a few extra pounds of materials used in building the structure, or the extra time we spent trying to refine the design; and much more to do with the complexity that so many of us (or our clients) are introducing into our structures. For good reason contractors like simplicity and repetitive details, member sizes and spacing, etc. With the advent of CAD and the various computer software, we can draw and design things which are very difficult the fabricate and build, and we don’t give that part of the process a second thought. We can design conc. beams in increments of 1" or .5" in depth, but then imagine the contractor farting around with new forms for every beam or the rebar faber. screwin around with different height ties for every beam, and then finally sure as hell the field guys will install the 16" ties in the 15" deep beam and not notice it until they are pumping conc. All to save an inch of conc.
Then, we seem to be having fewer and fewer experienced engineers doing and overseeing this part of the work, and more young engineers being able to tackle more complex designs without any, or enough, good guidance and mentoring on the whole process. Just consider many of the questions we see here on E-Tips, questioning much minutia, either code wise or detail wise, but the very nature of the questions suggests that the OP’er has very little understanding of the whole big picture. And, they apparently have no one to go to with their questions, or to gain a better understanding of the entire thought process of design; no one to draw them a sketch or explain that the change in weld detail on this one joint will cost many times, in detailing, layout, welder time, inspection and potential error, what might be saved in weld metal. And, the way we are approaching building codes and using computers for our design just contributes to this problem.
RE: Everyone Says the Structure is Overdesigned
The contractor may be correct but he is also very wrong because he doesn't know what the safety factor is at all or what it should be much less how much water is actually in the glass.
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MAP
RE: Everyone Says the Structure is Overdesigned
Just generally try to be helpful and understand where they're coming from, while firmly holding ground on what you need to hold your ground on and yielding a bit where you can yield.
RE: Everyone Says the Structure is Overdesigned
Another good one recently is with a manufacturer we work with…..he was so convinced I was wrong about an existing structure he said he was going to ask a “3rd party” who apparently was an independent consultant (structural engineer). I (politely) told him: good, he’ll tell you the same thing I just did. Sure enough, Mr. 3rd Party not only backed me……but said he wouldn’t mess with what I was doing for any amount of money. Classic.
RE: Everyone Says the Structure is Overdesigned
In the late 90's a friend was approached by a home owner who was getting the "I've been doing this for 30 years and I've never seen an engineer do blah blah blah...." from his contractor. He didn't like the steel moment frames around the garage door openings.
My friend looked over the drawings and calmly explained, "I'm sure he's right. We've been doing it differently and less expensively for at least 30 years. Then the Northridge earthquake happened and people died. Now, we do it differently." All that was needed was a simple explanation to the contractor and /or owner about WHY the design looks different than what they were expecting.
RE: Everyone Says the Structure is Overdesigned
Recently I had a client complaining about a slab on grade I designed. He had a tall racking system with 30kip post loads that he wanted to put on a 7" poly fiber reinforced slab. I called for it to be demo'd and replaced with a reinforcing 10" slab. He went on and on about how he had other warehouses with heavier loads and thinner slabs that were just fine.
I told him I couldn't put my reputation on the line just because he had been lucky in the past, and offered to investigate his existing slabs so I could explain what the differences were.