Constructability 2

[gwynn]

Partially out of curiousity, I would like to hear from those in purely design environments how much consideration is given to constructability.

Roughly %50 of my time is spent doing construction engineering (which probably means >%80 of my projects). As we do construction engineering and frequently have contractors as clients in design build projects, constructability is stressed as very important.

Many of the designs that cross my desk as a construction engineering project would get me a stern talking to from the boss if I tried to send them out to a client as a design, due to construction issues.

I see minor issues like easily avoided underhand field welds all of the time. It can be done, but it's a pain. The larger issues aren't quite as frequent, but things like pre-stressed girders which need post-tensioning on the top flange just to get them to site, circular concrete columns that are not a standard tube size and girders that cannot be erected singly still show up too often. Most issues like this that I come across can be checked early in design in under ten minutes, something that gets drilled into me every time I don't check something.

So, how much consideration do you give to such things?

 

[hokie66]

gwynn,

You are getting great experience, whether you choose to stay in construction or at some stage work in a design office. I believe constructability is at least as important as many of the other things that designers do routinely. It has always been a primary consideration for me, but unfortunately for all.

 

[JedClampett]

On the other hand, I spend a lot of time considering constructability and never hear word one about it from the owner or contractor. And worse yet, sometimes details where constructability was a factor are revised in ways that make them less constructable because that what's the contractor is used to.
It's a two way street. When's the last time any of you got a complement from a contractor or owner that this design was easy to build? I realize that it's our job to consider this, but a little positive feedback would work wonders. Because we certainly hear the negative.

 

[271828]

A LOT, well back when I designed anyway, and as Jed typed, it doesn't always pay off. There are some obvious design errors that should be avoided, but there are also lots of decisions that aren't so obvious.

For example, we designed several flat slab jobs and tried to make the drop panel depth a dimension that would be a wood 2x4 or 2x6 dimension to hopefully make it easier to build. One of our contractors told us that was better. A job or two later, the contractor wanted to know why the heck we did that!

Another one had to do with consolidation of steel beam sizes. We tried to group them as best we could, but were told later by one contractor that this approach was stupid, that they went straight by the weight and nothing else.

On one job, we caught a little flak in a meeting with the owner, architect, and GC, for over-consolidating (his opinion) the base plate sizes. I have no doubt that if we would've used 40 different base plate and anchor rod combinations, they would've screwed up some of the anchor rod placements and gave us crap over that.

 

[haynewp]

I consider it but I have also run into a couple cases where I tried to replace a lighter member for a heavier one and it came back on me. For example, a few years back I called for a constant depth open web steel joist size for several bays instead of switching to a lighter one as needed. I thought I was doing the best thing based on what I had heard at a steel joist presentation then a guy from vulcraft told me their price was based on weight.

You can also read a lot of things put out by AISC that try to get you to minimize connection costs by upsizing members but I don't know if it always gets an appropriate price reduction when it is bid, and more often I am afraid they look at weight. These kinds of things have come back on me a few times with someone thinking we had overdesigned the project. In fact, I would really like to know how other engineers feel about upsizing to save cost in such instances. I am sure it varies by region and the market of the contractor.

For all other cases where I control smaller field installation type things, I always choose the most constructable way. It is good to do this so when you go to the job site some guy is not asking 'WTF were you thinking'?

 

[msucog]

i'll chime in even though i'm not a structural guy. when i was a contractor, i had no problem checking between all the different sized things (base plates, bolt sizes, etc) to make sure i had my layout coorect. however, now that i'm with a testing firm, the contractors i see can barely read a set of drawings. they do not check dimensions, sizes, etc much less their own layout. so "dumbing down" the construction is a plus from the standpoint that the designer is somewhat more likely to get what they have drawn, but the contractor is able to get away with doing less and less. my opinion: if you go through the procedure of making things more uniform and constructable from the standpoint of having to assume that every contractor is dumb, then that's fine but don't make concessions when they mess something up and ask to for a fix to leave it in place.
i have seen things on drawings that were impossible to construct, but then again, we picked up the phone and discussed it with the designer to decide on the appropriate fix. today's contractors start screaming about change orders and delays. i feel that we (engineers interested in a productive project with a good quality product at the end) are often too easily convinced to accept something other than what we are normally comfortable with. i have taken the attitude that if the client or contractor feels they want a cheaper product with another firm, then that's where they should go. "cheap is cheap" is the motto we use. we might miss out on those revenues but then again we don't get sued over stupid crap for the sake of keeping someone with unrealistic expectations happy.
likewise, now that i'm with a testing firm, if the structural engineer will put out a letter saying they are satisfied with subpar test results, then that's their call...it definitely will not be my call.
please keep this in mind: for everything you see screwed up, there's 10 things just like it somewhere else. now just imagine if no one is watching at all........in other words, put your own considerations first and foremost because no one is looking out for you. to hell with anyone asking "WTF are you thing?". tell them to sign off on the design if they don't like it...that's my opinion for what it's worth.

 

[bridgebuster]

I worked about 12 years in the field as an inspector and resident engineer, and I'm still involved in construction support. When you see first hand things being built you realize constructability is important. I try to design things with the contractor in mind, but sometimes there's no way to make it simple.

As they say, "make something idiot proof and someone will build a better idiot."

 

[haynewp]

I am afraid it goes back into your reputation as an engineer and that of your company. The problem is that the guy that complains to me about how I showed something on my drawings also runs his mouth to everyone else that comes to the site. If I tell them they should have asked about that during bidding or they should have figured that their cost if it is extra labor, I don't think it always ends there. Eventually it can get back to your client.

 

[Dinosaur]

The last time I was thanked for putting a good set of plans together was over ten years ago. This is one reason I left design.

I wrote an extensive rant on this and then deleted it. Good Luck!

 

[msucog]

i can honestly say that i've never seen a perfect set of plans. but i've never seen a contractor not complain about every little details either (justified or otherwise). they complain that the columns are too big, they're overdesigned, details are too many pages back, column lines drawn on the page are not drawn heavy enough to see in the dark...you imagine it and i've heard it all since they usually complain to me when i'm doing inspections or testing materials. now, i'm not going to say that i've never seen horrible plans before, but then again when i ran in to something that didn't make sense, I PICKED UP THE PHONE AND CALLED THE DESIGNER.
as long as the designer and architects are making a real effort to not overcomplicate the design and thoroughly think through what's on the paper, that's all anyone can ask. if there's many real problems with the drawings, then the contractor should keep the guy that drew the things on the phone all day every day until the thing is built. i actually had a large job with 1000+ rfi's and almost 2000 sketches by the time the job was done. the architect finally put one of his guys on the job 3 days a week to work through the issues we had. there were several issues but many were somewhat unforeseeable or were a result of things having to be changed which started the snowball effect. sometimes, the job is complicated and just has to be worked through. we worked with everyone and the architect and engineer worked with us and we got the thing built on time with several months to spare and under budget (under budget from the contractor's standpoint--think the owner spent more than they were supposed to since they kept expanding the design). most contractors i see today could not have built that job like that. we were good and made 2.5mil in profits after all the bills were paid and had a good job (i wish i could've seen some of those profits to make up for all the long weeks and headaches).

 

[ryansteel]

I'm into pure design environment and for me I always consider constructability... but that doesn't get perfected... I guess RFI's will always be a part of the "CYCLE". a 20 storey job is transfered to me, as of this moment I have one core (of half the size and alongside the elevator shaft) that shows no openning, design show huge Mech ducts inside.... this is one nice example of not considering constructablility

 

[csd72]

If you are doing a design of something that you have done many times before, it is usually second nature to consider how they build it.

It is only on unusual buildings with construction stability issues that I would examine it in depth.

csd

 

[gwynn]

A very late reply on my part, but thanks to those who responded.

I chalk up the ratio of thanks for a good design to complaints for any design as human nature. I expect to get more complaints than thanks for anything I do. That said, I have received a number of compliments in the past months.

Hokie
I agree that I am getting great experience doing what I do. From the designs I see every day there are many things that some designers do not account for. For someone without years of experience it also means many more challenging and interesting problems.

I'm adding things to my lists of things to try to avoid or never do in a design on an almost daily basis. I beleive the latest is never design a composite beam that cannot support the weight of the slab before they are composite.

271828
I had a very simiar situation, where keyways where designed to allow use of one ripped 2x4. The precaster complained and we switched to a form requiring 3 or 4 seperate members in its place. Some people will always be stuck in thier ways. I would much rather deal with that than deal with trying to convince an old hand that the way they've always done things is no good anymore due to code changes.

I'm not too surprised to see most saying they consider constructability, those not doing so would be less likely to respond, and even further are probably less likely to spend time pursuing thier trade in off hours and hence not post on these forums.

From what I see consideration varies wildly from firm to firm. I almost dread getting a construction project when the design was done by certain firms. I know it will mean fights with both the contractor and designer to try to come up with something that works.