Reviewing Metal Building Drawings 1

[abusementpark]

When you are the EOR on a job that utilizes pre-engineered metal building framing, how closely do you review their shop drawings and calculations?

I am particularly asking about situations where the structure is more than just a metal building and there are a lot of miscellaneous structural steel attachments that put additional concentrated loads on the metal building frames or purlins. Even though I have clearly defined the additional loading criteria on the drawings, they are reluctant to show the inclusion of some these loads in their calculations. More recently, I had the engineer from a metal building company argue that he can say he doesn't need to consider a loading based on engineering judgement and that it is his prerogative to do that since he is stamping the drawings.

My opinion of these metal building suppliers is quickly diminishing. More and more architects are wanting to dress up metal buildings with all these different architectural features. However, I finding that from an engineering standpoint, these metal building suppliers can't handle anything that isn't their typical cookbook warehouse-type structure. It's like they can't deal with any kind of engineering calculation that their metal building program can't spit out.

Ok, end rant/

 

[JedClampett]

I spend a lot of time beating up PEMB designs on this forum. And I don't think that their designers can't handle special loads or requests. They're actually quite sophisticated designs and designers. It's that their calculations are so proprietory and mysterious that the EOR (you) can't figure out if they did it consider them or not. For instance, when strong armed by a client into using Pre-Engineered Metal Buildings, we need a monorail installed to move equipment around, we specify and locate this monorail. And the PEMB designer adds a couple of pages of hand calculations to his submittal package. But their normal software is so hard to figure out and the fact that they use special unique (with varying properties)shapes, makes me have to perform a leap of faith that the hand calculations meet the intent of the requested design.
I find myself reviewing their calculation packages by staring at them until I lapse into a coma and finally reviewing the column reactions and see if they're in the same ballpark I expect. Beyond that, you can't do much.

 

[woodman88]

All load cases need to be considered by the engineer. Now I have not done a calculation of a loading case based on my engineering judgement that the design will still work. I would provide such a calculation if needed but would first try a letter stating that the load case has been considered by me and that the design is structurally acceptable for this load case.

Garth Dreger PE
AZ Phoenix area

 

[Ron]

abusementpark...rant on, you've got plenty of company. Let's start with the EOR/Delegate process. As the EOR you delegate to the PEMB manufacturer the responsibility to respond to YOUR design intent, not theirs. If you have additional loads you want included in their design, they should do so...if not, reject their submittal. In my home state, the delegated engineering function is required to be responsive to the instructions of the EOR.

The PEMB engineer is not the EOR. While he can exercise engineering judgment in the analysis of his product, he has to consider your instructions...perhaps he is just using canned programs and doesn't know how to apply extraneous loading.

The PEMB engineer you mentioned needs to take a liability seminar!! As with many manufactured systems, engineering is secondary to profit in their world...he needs to wake up.

You call the shots as the EOR. Even though he signs/seals his plans, you are still responsible for the inclusion of his info into your intent and design. In the legal sense, it is specific reliance....you rely on him to provide calculations that meet the accepted standard of care and meet your design intent. Both are necessary.

Most of my structural analysis is either delegated work or failure analysis. I wouldn't dream of not applying the EOR's loading to one of the structures I analyze (usually aluminum specialty structures), and I've seen some reasonably outlandish requests! If it is way out of the ordinary, I'll usually call the EOR and discuss the need. Sometimes I'm able to convince him to look at other approaches..sometimes not. If I can't convince him, then the loads get applied and if it requires a beefier structure, then so be it.

Give 'em hell!

 

[msquared48]

I like your attitude Ron.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[pmtpemb]

I have been visiting this forum for quite some time, and gained much insight. My 2 cents... I work for a PEMB and can tell you that ALL loads specified by the EOR are included in our designs. We do not exclude any loads based on engineering judgement at all, and if we have any clarifications, we contact the EOR for info.

For instance when cranes are involved we create a load case for cranes, and all of our output clearly identifies where this load case is used in the various combinations.

If you use a respected PEMB supplier that has a proven track record, you will not have these issues.

Pmt

 

[Ron]

pmtpemb...thanks for chiming in. It's good to get the perspective of someone in the industry who does it right.

Unfortunately, my involvement with PEMB's these days is mostly in failure investigation. I have inspected many,many PEMB's and many of the contractors who put them up give the industry a bad name. It puts the manufacturer in a tough position...do you stop selling to the idiots...do you try to induce certain quality criteria through a contractor certification program (more than just financial screening)? Not sure of the answer.

 

[abusementpark]

Ron,

Perhaps, the problem with PEMB's not being built properly has to do with the lack of construction administration (i.e. site visits) from the PEMB engineer.

 

[JedClampett]

We (our company) designs complicated multi discipline projects where the metal building is there only to shelter a process. The projects bid (or use CMAR, which is even worse) to the lowest price supplier. Our involvement in picking a PEMB supplier ends at the specification. The contractor is trying to lower his bid as much as possible. And since the PEMB is pretty optimized already, there's very little room for reputable manufacturers to lower costs. So we get mom and pop outfits.
Maybe if the PEMB industry policed this a little better, this thread would be unnecessary.

 

[hokie66]

Jed,
As a process shelter, I would say the cheapest possible shed is poor economy. Why does your company do it that way?

 

[JedClampett]

The people doing the deciding are process people. They're trying to maximize value in their equipment and skimp on the building around it.

 

[pmtpemb]

well, the PEMB industry is governed somewhat - and I use the term loosely with MBMA.

Regarding contractors, that is where in my previous post I stressed using reputable PEMB companies. All of our contractors pass certification administered by a governing body.

Our district managers routinely go by the site and report back with anomolies.

Again not all companies are the same, some think about the bottom line only, and give the entire industry a bad rap.

PMT

 

[Ron]

abusementpark...in my experience, the only time the PEMB engineer shows up on site is if there's a significant problem.

pmtpemb...do you do site visits as a routine?

 

[j19]

Ron - you are correct that the metal building engineers usually don't show up unless there is a significant structural problem. But, and I think this was in a Modern Steel Construction article a couple of years ago, the metal building engineer should not be considered as the EOR. And this article was written by MBMA.

The metal building engineer depends on an EOR, or some other design professional, to specify any nontypical loadings such as cranes, RTU's, special piping, etc. And if the metal building engineer won't produce a letter certifying the loads that the building was designed for, or if he/she won't discuss with you where the loads are shown in their voluminous set of calcs, raise **** with the building official or owner or whoever hired you.

 

[paddingtongreen]

Much depends on the contract details. I am used to writing a spec, basically calling on the codes and MBMA with drawings of interfaces and applied loads etc. The bidders are required to list any exceptions with their bid. They are always, again in my experience, required to have their work sealed by a PE in the state where the project is to be built. If their work is sealed, I would only review for the fittings provided for the interfaces, and I state this on the review drawings and provide comments on those items, or say I have no comment. Legally, if I approve their drawing, or look at the calculations, I share responsibility. In these days of bottom line awards, I will not have any manhours available for reviewing their design.

Do I do this with an easy heart? hell no, I suspect that some of the PEs that seal these jobs rent out their seals for a fee.

I have worked jobs where the client decides to go pre-engineered partway through the job, and takes away the manhours associated with that task, leaving nothing for a design review.

You have to CYA while keeping the client's lawyers and bean counters happy.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[Ron]

Michael...in some states, it doesn't matter if you reviewed their design or not...you still have some responsibility. As the EOR, you dictate the parameters. You have to at least check to see that the parameters were fulfilled. If you don't it violates your standard of care...which lawyers take to imply..negligence. The engineering laws are written without regard to profit, so they expect some level of review.

Ron

 

[EEJaime]

We have similar issues from a non-structural element which must be supported by the building. We often have quite a lot of equipment that needs to be supported by the building structure, from roof mounted equipment to mechanical equipment, plug-in busway, crane rails, etc.... We have our standard mounting and seismic bracing details for most common types of construction, but when it comes to PEMB's the structural members are quite often unique, proprietary sections that we do not have specific data for. Additionally, we will not know which PEMB supplier will be the successful bidder, so we need to detail a 'generic' connection that 'should' cover the final configuration, but most often does not.

We recently did a Sheriff's department Helicopter maintenance facility in Los Angeles County. We had overhead light reels, lubrication reels, equipment, heaters, conduit racks, etc.... We detailed the supports to include spreader channels so that we would not attach directly to the bulding 'z' purlins as they were fairly light weight in the designed system. As it turns out, a different manufacturer recieved the contract, used even lighter members than those specified and wanted a change order to beef up his 'standard' structure to support all the added steel. I am not sure how this particular issue was resolved as the Structural EOR fought it out, but the County Fire Department was not happy.

It just seems these structures create situations which are almost 'Catch 22' in nature. No matter how much one thinks one has planned ahead, the very basis for the planning can go out the window when the actual supplier is identified. And there is the occasional "it's not in my scope" between the PEMB Structural and the project EOR to add to the fun.

I guess it is one of those issues that will never be universally resolved, but which must be addressed as thoroughly as one can, when it arises.

Regards,
EEJaime

 

[FFENGINEER]

I think that whoever has the majority of the structure should be EOR. I.E, PEMB engineer is EOR and they need to shop out the foundations...I know there are reasons not for this, but it would add some validity to their designs

 

[NITTANYRAY]

The most frequent problems that I have encountered have to do with wind exposure category and drift loads from adjacent buildings or a different portion of the same building.

Most programs can only handle rectangular buildings. Larger irregular shaped buildings are treated as several smaller buildings. If one happens to be higher than the other the lower building is often designed for drift loads. If the shop drawings don't have purlins spaced closer together near drift areas that usually raises a red flag for me. Sometimes they will increase the gage of the purlins but that info is not always readily apparent on their drawings.

I once had a metal building designer say that he always used exposure B because 80% of the buildings in the country fall under that classification. What he failed to realize is that a large percentage of metal buildings are erected on the perimeter of developed areas where the land is cheaper and more readily available. These areas are more frequently exposure C.

 

[ToadJones]

This might be off topic slightly and I'll admit that outside of actually erecting a few PEMB in the late 1990's, I have limited experience with them.
What I have always wondered is what design criteria manufacturers of PEMB follow as far as deflections and general seviceability.
Just last week a friend of mine who works in a brand new office that is a PEMB frame called as he and his co-workers were alarmed to see that the ceiling tiles along the walls (where the tiles were supported by the tracks on the partitions) were sloped 1.5" in just two feet and the sprinkler head escutcheons had moved a few inches.
We had just gotten about 8" of snow. He said there was at most 8" of snow in the roof. Upon looking at some pictures of the frame as the building was being erected I could that the PEMB frame was spanning about 100'. The building owner, who was also the builder, brought his engineer who said that that sagging tiles were so because of the snow load on the roof and it would go away when the snow melted or was removed. The next day, his crew shoveled the roof and the ceiling tiles returned to normal. Running quick numbers for span & deflection and I could see where 3" or more of roof deflection was permitted, but does this really provide good serviceablity?
I would say NO.
The building was designed to the gnat's ass and was essentially a cookbook building. It may well be that the building is safe, but it obviously performs poorly. I don't care how "sophisticated" PEMB software might be...it might be too sophisticated.
The people in the building are not comfortable and the building manager has to have someone straighten out ceiling tiles every time it snows 8"....fairly often in the NE.