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metal building versus conventional steel framing

metal building versus conventional steel framing

metal building versus conventional steel framing

(OP)
What is anyone's experience with cost comparisons between a conventional steel framed structure versus metal building framing.  Not pre-engineered metal building, but a custom building using metal building components.  Conventional steel framed building is hot-rolled wide-flanged beams and columns, bar joist and metal deck roof, cold-formed stud walls.  Custom metal building is one that does not utilize the metal wall and roof panels, but a different veneer system such as brick and a standing-seam roof with rigid insulation.  I work with several architects who believe that as long as the structural framing is metal building components, the building costs must be significanly less.  I contend that as long as the owner uses an off-the-shelf pre-engineered metal building with no modifications, that is the most economical.  When either system is custom designed, there really is not a signifant difference in cost between a custom metal building and a conventional steel framed structure.  Assuming the foundation is essentially the same regardless of framing system.  I know there are alot of variables involved, but wondering if in general terms, am I off base here?  Looking at the RS Means data, I believe I am correct.

RE: metal building versus conventional steel framing

"I contend that as long as the owner uses an off-the-shelf pre-engineered metal building with no modifications, that is the most economical."

For smaller metal buildings, what you say is more than likely true.  

However, for large metal buildings, throw off-the-shelf out-the-window.  Each of these buildings is one of a kind in structure, orientation, foundation, and load application.

That being said, I still feel that a PEMB will be cheaper.

Mike McCann
MMC Engineering

RE: metal building versus conventional steel framing

As much as I hate to say this, I doubt that we (structural engineers) can compete with a building using metal building component framing.  Maybe a joist/joist girder building could be cheaper, or as cheap.

We had a case where we were designing a paper manufacturing facility and had started the conventional steel framing analysis as had been successfully done several times before.

The contractor was chosen and "value engineered" the switch to a metal building.  This was a 2-story structure with a 3rd level of equipment access mezzanines and two building cranes running the full length for production and maintenance lifts.

Just remember that you are not comparing apples to apples.

They use the MBMA standards rather than AISC and do some things that do not necessarily make total sense.  The shell and the crane support were done as a "metal building frame".  The 2nd floor and equipment mezzanine were done with conventional steel framing, but beams were not on the frame lines.  Two conventional columns straddled the frame columns, but shared common footings.  In addition, beam spacings were varied so that the same structural shape could be used to carry differing or specialized loads throughout the structure.  This played havoc with the process and electrical designs being done simultaneously for installation after the floors were poured.

Their approach saved money and expedited the schedule which proved to be a no-brainer to the Contractor and the Owner.

GJC
 

RE: metal building versus conventional steel framing

"They use the MBMA standards rather than AISC and do some things that do not necessarily make total sense."

This is only partially true.  They do have MBMA documents, but follow the AISC Spec. and AISI Spec. to the letter.   

RE: metal building versus conventional steel framing

archeng59, you asked if your thinking is off.  I think the classifications of types of MBs are off.  I used to work for a MBMA member and have done consulting for one for years.  To my knowledge, practically all metal building systems are custom designed at this point.  There might be some specialized application that uses "off-the-shelf," but that wouldn't be what we'd think of in 2009 as a metal building system.  A MB system can have metal panels, brick, CMU, etc. as the cladding--it's still a metal building system.

I'm pretty confident that for the vast majority of low-rise designs, the MB system's *strutural system* will be cheaper than the conventional system.  Their in-house design programs and design aids optimize the structure to an extent that EORs would never dream of for a conventional bldg.  When's the last time you used a build-up member for a floor beam and changed the flange and web plate sizes multiple times in 30 ft?  Never, I know, because it wouldn't make sense with a conventional fabricator.  It does for MB companies, however.  I've seen this in a MB mezzanine.  Like MTU pointed out, there are situations in which their products are awkward.

RE: metal building versus conventional steel framing

(OP)
I'm unconvinced that 100% of all MB's are custom, but I believe that because architects are trying to use MB systems in buildings that are not rectilinear boxes that many MB's are custom.  So is the term "pre-engineered" is really obsolete for the most part?

For buildings where the owner will be hanging things from the roof structure and those suspended items will be moved around and changed several times per year, is a conventional system (joists and metal deck roof framing) more suited to that functionality versus a metal building system?  It seems that attaching wires or other hangers from bar joists would be easier than attaching hangers from z-purlins.

 

RE: metal building versus conventional steel framing

Yes - the Z pulins were another area of contention.  We knew we had some areas with roof top equipment where conventional steel sections would be more vesatile - but that did not fit their normal way of construction.

GJC
 

RE: metal building versus conventional steel framing

Metal building companies might follow AISC & AISI, but they sure have their own deflection criteria. That way you can create high strength steel tapered frames with webs so thin they can't even properly keep the flanges from buckling, and you can let the frame deflect H/60, or whatever other number is convenient, so that deflection never controls the design.

RE: metal building versus conventional steel framing

PEMB's are generally less costly.

There are several issues with the cost savings (these are general and not necessarily applicable to your installation).

You cannot get after sales service.  Any modifications you are strictly on your own.

As noted above, they often do not follow the same standards of most steel buildings. They are an entity unto themselves.

Any modifications will likely void any warranty you might have had.

They are difficult to modify and substantial cost can be expected from both engineering as well as fabrication.

They do not accommodate future loading easily, unless stipulated in the design requirements. Design check is costly.

Consider them as 25 year 'throw away' items.

In earlier threads, I've posted my standard notes for PEMB's. Tightening up the requirements bumps the cost up significantly.

Experiences from several years ago:
A 3psf added load for sprinklers resulted in a $12,000 extra.
A lower girt to provide lateral support for a 4' high masonry wall was designed for an L/90 deflection. I don't recall if the span was 25' or 30'... also, an extra.
A buiding that was used for a chemical process had roof deck corrosion that necessitated substantial re-roofing. The cost was in excess of $280,000 and the firm packed up its tent and left the town.
Removing an end support required reinforcing the structure two bays distant in addition to the end bay.

Dik

RE: metal building versus conventional steel framing

"I'm unconvinced that 100% of all MB's are custom, but I believe that because architects are trying to use MB systems in buildings that are not rectilinear boxes that many MB's are custom.  So is the term "pre-engineered" is really obsolete for the most part? "

LOL, you can be unconvinced and wrong at the same time!  Just joking and some ribbing there.

If you design a building that is a single gable box, every MB company I know will run that through their programs and design it to death in a custom kind of way.  It's impossible to prove non-existence, so I don't know if someone out there would have these "off the shelf," but I doubt it.

When you're referring to MBMA type bldgs, I'd say "pre-engineered" is indeed an obsolete term.

"For buildings where the owner will be hanging things from the roof structure and those suspended items will be moved around and changed several times per year, is a conventional system (joists and metal deck roof framing) more suited to that functionality versus a metal building system?  It seems that attaching wires or other hangers from bar joists would be easier than attaching hangers from z-purlins."

I'd agree with that.  Heck, I'd put bar joists into the "less than desirable" category for that type of application also.  So if a guy wants to move an 800 lb load to another location, he has to reinforce the joist accoringly.

RE: metal building versus conventional steel framing

Spats wrote "Metal building companies might follow AISC & AISI, but they sure have their own deflection criteria."

This is supposed to be some kind of evidence of what?  Deflections are not usually codified and conventional engineering offices often use different values.  They just happen to have studied, in detail, what they really need for their types of buildings.  Some kind of problem with that?!  They use tighter limits when they need to, such as when they have brick cladding.

"That way you can create high strength steel tapered frames with webs so thin they can't even properly keep the flanges from buckling"

Come one now.  Not to sound harsh, but this seems to illustrate a lack of understanding of slender plate girder design by the AISC Spec.  So bridge engineers who use slender plate girders operate in a similar cowboy-ish manner, LOL?

RE: metal building versus conventional steel framing

(OP)
Thanks for all the input.   

RE: metal building versus conventional steel framing

Dik: "As noted above, they often do not follow the same standards of most steel buildings. They are an entity unto themselves."

I don't know what you guys mean by "different standards."  They design their bldgs to specifications adopted by the building code, period.  This means the AISC Spec. and AISI Spec.  They have MBMA specific guidelines also, but those are the "specs" that are used.

Can't argue with the rest of your post.  MBs definitely have their limitations.  *IF* one is in the position to shell out the dough for a building within those limits, then he's *thankful* that MBMA folks operate the way they do.  The economy makes it possible for some folks to go into business to do their thing.

RE: metal building versus conventional steel framing

Guys, sorry to sound combative.  I have a soft spot for MBMA types because I've worked with them.  These discussions usually end up in a bash-fest from folks outside their industry.  I know guys from 4 of these companies and they are great guys who really like to do a good job.  Their products are great for some kinds of projects and awful for others, but I think we could say that about any system.  They know this, but if the project is borderline and the GC wants to push for a MB, they ain't gonna turn them down, LOL.

RE: metal building versus conventional steel framing

Sorry, I didn't mean to sound so jaded, but facts are facts. By the way, I worked for a metal building company for 8 years, about half of that time in their product development department.

271828 wrote "They just happen to have studied, in detail, what they really need for their types of buildings.  Some kind of problem with that?!". I am currently working on a metal building project with (2) 20T bridge cranes, and their "studied need" called for H/60 deflection on the main frames and portal frames (their "standard"). I also have masonry walls to 10' high all around. I don't think anybody other than PEMB folks would think that kind of deflection is appropriate.

With metal buildings being used more-and-more with conventional wall systems and unusual loadings, it's about time they reconsider their standard deflection criteria, among other things. Of course, they don't want to compete by the same rules as the rest of us, because then they wouldn't be able to steal as much work from us conventional designers. They convince owners and contractors that they get the same quality of building, because it "meets code", but this is not true in my book. As mtu1972 said earlier, we "are not comparing apples to apples".

RE: metal building versus conventional steel framing

(OP)
My question started with a discussion between me and an architect.  We are working on a project where the owner will have various events in the building that will require signs, marquees and various displays suspended from the roof framing.  Most of the suspended weights will be less than 500 lbs per hanger.  The architect wants to use a metal building to reduce costs.  Both his fees to consultants and final construction costs.  In my opinion, a metal building does not offer the owner the flexibility to hang things inside the building wherever he wants to based on the events he has discussed.  I recommended a conventional steel braced frame system with bar joists and metal deck roof framing.  The architect said metal building framing is always more economical.  I agree to a point, but not for this building.  When all is said and done, the rigid frames, portal frames and roof purlins will be the only metal building components in the building.  The architect does not want girts even though I explained that the girts serve as lateral bracing for the columns.  I lost the battle on this job.

Anyway, thanks for the input.

RE: metal building versus conventional steel framing

I wouldn't blame the PEMB industry exclusively, except for the fact that they throw away their calculations minutes after being paid for the project.  
You can't tell me that when owners are pushing for the cheapest product out there, that they don't know that they're getting a less durable building.  These aren't stupid people.  They want to make budget and let the next guy worry about the lifespan, dings, recoating, swaying fixtures and fact that you can't hang a 500 lb. lifting eye from the structure.  
When you pay Yugo prices, you get a Yugo.

RE: metal building versus conventional steel framing

Great set of comments!!!! - I completely agree with both sides on this. Being a crane guy, I would caution against excessive deflections in any part of the structure. This could lead to premature crane wheel & bearing problems; that nobody will think is the building's fault. Also, it's nearly impossible to prove, if the building becomes an item of discussion.

RE: metal building versus conventional steel framing

Whose fault is it when the MB is designed to deflection limits that are too loose?  I've worked on MB projects from both sides.  The EOR's structural notes should indicate the appropriate deflection limits when soemthing other than MB typical values are not OK.  I've done this lots of times and they've complied without any issue every time.

Do you guys not do this?  If not, then I'd suggest that the fault is not only the MB engineer's, LOL.

RE: metal building versus conventional steel framing

Lots of great comments since I made my earlier posting.  I should have been more specific when I mentioned standards as I was not questioning strength, but was concerned about lateral stiffness.  And yes those may not be codified standards but we all know and try to comply with them.

The Contractor had considerable problems with getting the crane runway girders aligned and indicated that regardless of what future Metal Building guys say, he would never put up another industrial facility without grouting the column base plates to help with squaring and aligning the structure.  They had ridiculously thin base plates and no grout to our foundation piers.

JedClampett is totally correct when he says the Owner made the choice to help insure staying On-Time and Under Budget, so it's on him when the future inevitable changes become difficult and costly.

The Contractor pushed for this decision because it took all of the shop drawing review, siding, and roofing submittal time factors off of his plate and out of the project schedule.

From our standpoint, we were on a T & E Not-to-Exceed contract and we lost out on about 2 people's billing time for the steel design.  One senior designer was still required full time to interface process requirements and keep our CAD model up to date with the structural framing.

GJC
 

RE: metal building versus conventional steel framing

You can't tell me that when owners are pushing for the cheapest product out there, that they don't know that they're getting a less durable building.

There are some owners who realize this and seek lowest cost over longterm performance, but I really think that most owners don't know what they're getting.  What they hear is "our building meets code".  That's true, but code minimum does not equal durability and serviceability.

 

RE: metal building versus conventional steel framing

mtu1972... you aren't doing something to the building that will void the warranty? are you? Gotta be careful.

Dik

RE: metal building versus conventional steel framing

It's been my experience that owners and architects don't realize that PEMBs engineer right down to the nut. Generally speaking you get the absolute minimum factor of safety on every component.

We had a PEMB with modifications made (by others) to the columns, but the factor of safety was cut so close the modification ended up in a catastrophic failure (and lawsuit). My opinion is that almost any conventionally framed building would have easily survived the same modification.

It seems to me that PEMBs (and gas station canopies for that matter) suffer a disproportionate number of failures due to the fact that they cut it so close. Even designed to the same codes, the effective safety factor is less for a PEMB than a conventionally framed building, but the Codes were written around conventionally framed structures. Each PEMB component is skinnied down to the limit. Stability bracing is right on the edge. Deflections are run to the limit and are often based on a 10-year wind. Watch the Weather Channel and look for the crumpled Pre-Eng buildings and fly away gas station canopies.  

RE: metal building versus conventional steel framing

JLNJ, so if I understand you correctly, you're condemning MBMA companies because one designed and sold a product to an owner that was presumably exactly what the owner wanted and satisfied published codes, specs, and standards and then someone else came in and did one of the following:

1. Modified the structure and didn't run design calcs to make sure it was OK or

2. Modified the structure after incorrectly running design calcs, screwing up, and incorrectly determining that it was OK.  

I don't follow your logic.  I've worked on plenty of conventional bldg projects in which we modified the existing structure.  It was MY responsibility as the new project EOR to make sure *I* wasn't going to cause a problem.  You and several others in here seem to me like you're intimidated dealing with and competing with optimized designs, so you'd be happier if everybody else was too.  In my experience, that kind of thinking doesn't lead to a very robust business model!

Not just to you, but to everyone else in here also:

If MBMA companies have it all wrong, then why don't you get together and start a competing trade organization?  You could call it SMBMA (Strong Metal Bldg Manufacturers Association) or some other catchy name.  Design your bldgs to tighter deflection and drift limits and avoid the use of slender elements.  Heck, avoid the use of any element that requires more than Steel I to design, so that other folks won't come in later and struggle trying to figure out if they can safely modify it.  Use only CMU, precast, brick, EIFS, etc. cladding and no cheap metal panels.

I think you guys should be able to sell the concept to owners, GCs, and architects.  If you're just in here for a gripe and whine session, then forget the suggestion.  Griping and whining is something that I think of being done by old gossips with nothing better to do, not highly educated professionals.

RE: metal building versus conventional steel framing

dik -

I'm not doing anything to the building.  I specified the loads, including all specialized equipment, etc. and our designer provided interface on pipe chases, pipe racks, etc.

They were direct hired by the Contractor (who was really a Construction Manager) and we had several coordination meetings as to where and how we would do thickened floors, etc. if the building were convetionally framed.

Thanks for the warning about the warranty though - because invariably we will be called in for rebuild upgrades.


271828 -

I realize that this will become all the more prevalent as the years progress.  Let's face it, the buildings Metal Building groups did in the late 70's into the 90's were usually simple rectangular boxes.  But they now have dedicated staffs, state of the art computer modeling abilities, and the where-with-all to realize that there was a huge untapped market out there.


Still one thing really bugs me, and that is putting a grid line at the face of the girt.

GJC
 

RE: metal building versus conventional steel framing

"Still one thing really bugs me, and that is putting a grid line at the face of the girt."

NO argument there!

RE: metal building versus conventional steel framing

Best get your loading in place now... make sure that the purlins can support 500 lb loads at any three points and that the building frame can accommodate 2000 or 3000 lb loads at anywhere as well as 1000 lb lateral loads at any location along the vertical leg of the freame, etc.  Modify above loads to suit. I'll repost my pre-eng building notes below:

METAL BUILDING SYSTEM (PRE-ENGINEERED METAL BUILDING)

DESIGN STANDARDS FOR THE METAL BUILDING SYSTEM ARE TO MEET THE REQUIREMENTS OF PART 4 OF THE MANITOBA BUILDING CODE AND CSA S16 AND CSA S136

ALL STRUCTURAL STEEL COMPONENTS, INCLUDING ANCHOR RODS SHALL BE CERTIFIED AS WELDABLE

PREFABRICATED METAL BUILDING SYSTEM SUPPLIER SHALL SUPPLY ALL ANCHOR RODS, NUTS AND WASHERS TO SECURE THE BUILDING TO THE FOUNDATION. ANCHOR RODS ARE TO BE DESIGNED FOR ALL HOR AND VERT LOADS

DESIGN OF THE BUILDING FRAME AND ALL COL MEMBERS SHALL ASSUME THAT ALL FRAME AND COL BPS ARE SUPPORTED ON 1" OF GROUT. ANCHOR RODS SHALL HAVE A MIN 3" PROJECTION ABOVE THE BP AND SHALL HAVE A MIN EMBEDMENT LENGTH AND CONFIGURATION TO RESIST ALL SHEAR AND UPLIFT FORCES

FABRICATION SHALL BE IN ACCORDANCE WITH CSA S16 AND CSA S136, AS APPLICABLE. WELDING SHALL BE PERFORMED IN ACCORDANCE WITH CSA W59 AND CSA S136. MANUFACTURER TO BE APPROVED BY THE CANADIAN WELDING BUREAU, IN ACCORDANCE WITH CSA W47.1 FOR DIVISION 1 OR DIVISION 2

THE BUILDING SHALL CARRY A 25 YEAR ROOF WARRANTY AND A 15 YEAR SIDING WARRANTY AGAINST DEFECTS IN MATERIALS AND SHALL CARRY A 5 YEAR WARRANTY AGAINST DEFECTS IN WORKMANSHIP

MIN ROOF SLOPE SHALL BE 1/2:12

THE BUILDING SHALL BE DESIGNED FOR THE FOLLOWING LOADS IN ADDITION TO THE LOADS STIPULATED IN NOTES FOR DESIGN LOADS:
  ROOF PURLINS:   DEAD LOAD = 5 PSF UDL
                  LIVE LOAD = 5 PSF UDL AND POINT LOAD OF 250 LBS SUSPENDED FROM ANY LOCATION
  BUILDING FRAME: DEAD LOAD = 1000 LBS SUSPENDED FROM ANY LOCATION
                  LIVE LOAD = 2000 LBS SUSPENDED FROM ANY LOCATION
                
PURLIN BRACES ARE TO BE PROVIDED IN ACCORDANCE WITH CSA S136, CLAUSE 8. IN PARTICULAR, FOR A STANDING SEAM ROOF SUPPORTED ON MOVABLE CLIPS, BRACES PROVIDING LATERAL SUPPORT TO BOTH TOP AND BOT PURLIN FLANGE ARE TO BE PROVIDED. THE NUMBER OF ROWS SHALL BE DETERMINED BY ANALYSIS BUT IN NO CASE TO BE LESS THAN 1 FOR SPANS UP TO 23 FT. OR LESS THAN 2 FOR SPANS GREATER THAN 23 FT

ALL STRUCTURAL STEEL SHALL BE PRIME PAINTED. IF A PAINT TOP COAT IS REQUIRED, PRIMER SHALL BE COMPATIBLE WITH THE TOP COAT

ALL ROOF PURLINS AND WALL GIRTS TO HAVE A ??? COATING CONFORMING TO ???. COLOUR SHALL BE SELECTED BY THE CLIENT FROM THE MANUFACTURER'S LIST OF STANDARD PROVEN COLOURS

ALL ROOF PURLINS AND WALL GIRTS TO HAVE BE HDG WITH A COATING CONFORMING TO Z275

ALL ROOF CLADDING SHALL HAVE A COATING CONFORMING TO CSSBI [SERIES 5000 | SERIES 10000 | BARRIER | METALLIC/ELITE SERIES]. COLOUR SHALL BE SELECTED BY THE CLIENT FROM THE MANUFACTURER'S LIST OF STANDARD PROVEN COLOURS

ALL WALL CLADDING SHALL HAVE A COATING CONFORMING TO CSSBI [SERIES 5000 | SERIES 10000 | BARRIER | METALLIC/ELITE SERIES]. COLOUR SHALL BE SELECTED BY THE CLIENT FROM THE MANUFACTURER'S LIST OF STANDARD PROVEN COLOURS

ALL LINER PANELLING SHALL HAVE A ??? COATING CONFORMING TO ???. COLOUR SHALL BE SELECTED BY THE CLIENT FROM THE MANUFACTURER'S LIST OF STANDARD PROVEN COLOURS

ALL LINER PANELLING SHALL HAVE A GALVALUME COATING CONFORMING TO ZF075

COLOUR OF TRIM, RAKE, EAVESTROUGHING AND DOWNSPOUTS SHALL BE SELECTED BY THE CLIENT FROM THE MANUFACTURER'S LIST OF STANDARD PROVEN COLOURS

THE BUILDING SHALL BE INSULATED AND THE PREFABRICATED METAL BUILDING SUPPLIER SHALL SUPPLY ALL NECESSARY THERMAL BLOCKS. INSULATION SHALL BE PROVIDED BY ???

DEFLECTION OF WALL AND ROOF CLADDING SHALL BE IN ACCORDANCE WITH THE REQUIREMENTS OF CSA S136-94

DEFLECTION OF WALL GIRTS AND ROOF PURLINS SHALL BE IN ACCORDANCE WITH THE REQUIREMENTS OF CSA S16. IN ANY EVENT, LIVE LOAD DEFLECTION SHALL NOT EXCEED L/240. THE METAL BUILDING SYSTEM SUPPLIER SHALL PROVIDE FOR SUPPORT OF ANCILLARY STRUCTURAL ELEMENTS WHERE NOTED ON THE DWGS. THE METAL BUILDING SUPPLIER SHALL PROVIDE FOR REDUCED DEFLECTION LIMITATIONS AS REQUIRED FOR ATTACHMENT TO OTHER BUILDING COMPONENTS

SHOP AND ERECTION DWGS OF THE METAL BUILDING SYSTEM, BEARING THE SEAL OF A PROFESSIONAL ENGINEER REGISTERED IN MANITOBA, ARE TO BE SUBMITTED TO THE [CONSULTANT | ENGINEER] FOR REVIEW PRIOR TO THE PLACEMENT OF FOUNDATIONS. SHOP DWGS ARE TO PROVIDE LOCATION OF GRID LINES, AB CLUSTERS, AND SIZES. ANCHOR ROD AND BASE PLATE DESIGN SHALL ASSUME THAT BASE PLATES ARE SUPPORTED ON 1" GROUT

THE CONTRACTOR SHALL SUBMIT SHOP DWGS PRIOR TO FABRICATION FOR THE [CONSULTANT | ENGINEER]'S REVIEW. UNLESS NOTED OTHERWISE, SUBMIT SHOP DWGS AS FOLLOWS:
  1 SET OF DWGS ON REPRODUCIBLE VELLUM
  1 SET OF DWGS IN DIGITAL FORMAT
  2 SETS OF PRINTS MADE FROM THE REPRODUCIBLE VELLUM

A SHOP DWG SHOWING THE ANCHOR SETTING LOCATIONS FOR THE BUILDING MUST BE PROVIDED. THIS DWG SHALL SHOW:
ANCHOR ROD LOCATIONS, TYPE, DIA, PROJECTION AND LENGTH, MAX AND MIN REACTIONS BASED ON THE LOAD COMBINATIONS STIPULATED IN THE MANITOBA BUILDING CODE SHALL BE PROVIDED FOR ALL SUPPORTS (A TABULAR FORM SHOWING LOADING REACTIONS FOR VARIOUS LOAD CASES IN NOT ACCEPTABLE)

COORD X-BRACING ELEMENTS WITH ARCH TO PREVENT CONFLICT WITH OPENINGS

THE BUILDING SHALL BE COMPLIANT WITH THE REQUIREMENTS OF ASHRAE 90.1

THE BUILDING SHALL BE COMPLIANT WITH THE REQUIREMENTS OF THE CURRENT NATIONAL ENGERGY CODE

THE BUILDING SHALL BE COMPLIANT WITH THE REQUIREMENTS OF FM GLOBAL FOR AN I-60 RATING

THE BUILDING SHALL BE COMPLIANT WITH THE REQUIREMENTS OF FM GLOBAL FOR AN I-90 RATING

THE METAL BUILDING SYSTEM MANUFACTURER SHALL SUBMIT THE CSSBI CERTIFICATE OF DESIGN AND MANUFACTURING CONFORMANCE TO THE [CONSULTANT | ENGINEER] PRIOR TO SHIPMENT OF THE PREFABRICATED BUILDING TO SITE

Bend and mutilate as necessary...

Dik
 

RE: metal building versus conventional steel framing

271828

My post does not "condemn" the MBMA or claim that they have it "all wrong". MBs are sold mostly based on cost. Those MBMA companies have done a great job with that business model- there's no doubt about it. However, lowest cost comes with its drawbacks and penalties and many owners and architects don't understand those penalties.  

RE: metal building versus conventional steel framing

JLNJ, I agree with your last post.  MB systems definitely have limitations and get used incorrectly at times.  Some owners might get fooled or led down the wrong path.  In my limited experience with owners I've known personally, they knew what they were getting and were happy to save a few tens of thousands of bucks that they could pour into something more productive than bigger columns and more durable cladding, LOL.  I'd assume that most folks with enough drive to buy a bldg for a business are smart enough to know what they're getting, but maybe I'm wrong.

What I was referring to was:

"We had a PEMB with modifications made (by others) to the columns, but the factor of safety was cut so close the modification ended up in a catastrophic failure (and lawsuit). My opinion is that almost any conventionally framed building would have easily survived the same modification. "

I'm not a mind reader, but this seems to be an attempt at putting blame on a MB company where I'd argue that the EOR who agreed to the modifications is more directly at fault.

Put it this way: Say I design a concrete flat slab for 60 psf LL and I optimize it down to the last rebar and cutoff length.  The punching shear ratio is 1.000 and long term deflections are right at whatever we'd say is the max reasonable limit.  Now some owner wants to use it for a heavy storage area with much large LL.  The new EOR approves it for some bizarre reason and it has some kind of problem.  It's not my fault for optimizing it to the nut, as one guy put it.  It's the new EOR's fault for either not checking it or not knowing how to check it--neither of which is the first EOR's fault

RE: metal building versus conventional steel framing

was there an EOR involved? I would say not and this is where the problems come about, with modifications. The public expect to be able to make some minor modifications without having to go to the next level ie getting an EOR on board.

The problem is so big with this type of structures in my area, that the local steel association has decided to put out a minimum standards book, because engineers where cutting it too fine. Relying on cladding without doing fatigue analysis/testing for shear loading ect.  
 

Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that them like it

RE: metal building versus conventional steel framing

What minor modification could be made to a MB column that would cause catastrophic failure?  I can think of only one that an unsuspecting owner might *reasonably* consider harmless, but would be dangerous, but it's a long shot.

RE: metal building versus conventional steel framing

I've encountered many PEMB's that have been modified by the owner without realising that they were reducing the strength of them.  One I'm helping a junior engineer with right now has a series of 3 overhead cranes that have been added in the past without engineering and they wanted to add another 2...

Many owners don't appreciate the level of 'fineness' in the design of these things and think it's like banging a nail in the wall to hang a picture.

Dik

RE: metal building versus conventional steel framing

Metal buildings do not necessarily have a higher rate of failure than conventional buildings because they are designed skinny or because they are abused by modification. They primarily fail under high wind loads, such as a hurricane. When the exterior skin is breached, and significant wind loads get INSIDE the building... that's when all hell breaks loose. In other words, the building envelope is primarily the culprit.

RE: metal building versus conventional steel framing

I don't see how this has anything to do with the bldg type.  Is it not possible that an engineer would design a conventional bldg with optimized crane runway beams?  That's all it would take to cause problems if a larger crane was added.  It wouldn't matter if the rest of the bldg was made of heavy reinforced concrete.  

I know if I was hired to design a bldg with a 10 ton crane with whatever wheelbase, etc., I'd design a good beam for that situation.  It's not my fault if the guy comes in with another 10 ton crane or replaces his crane with a 50 ton one.

RE: metal building versus conventional steel framing

271828

The jury on final word on the cause of the failure is still out. Our firm was involved just on the very periphery and I'm not sure of the final ruling or if there has been one yet. The leading indicators show that it was a column or "knee" compression flange failure due to inadequate lateral bracing. There are other complicating issues as well which involve some modifications over time and bit higher load than might have been originally anticipated.

My contention is NOT that the PEMB manuf designed things improperly, but rather by its very nature a PEMB often has a lesser safety factor. Most of the time we don't know just how close we come to using up all that reserve strength - and sometimes we find out quite suddenly. The 1.6 safety factor was developed in a time before MBs really got their foothold. Maybe the 1.6 doesn't provide the same reserve strength from framing system to framing system. In the case I cited, several circumstaces chewed into the reserve capacity/safety factor, eventually causing failure.  

RE: metal building versus conventional steel framing

JLNJ, since it was a failure of the compression flange, had a flange brace or girt been removed, or the elevation changed.  The most common cause for failures in PEMB is flange braces either being removed or not installed as indicated.

Do we design our buildings right on the edge?  You better believe it.  But we provide exactly what is in the Contract Documents.  The entire discussion about deflections/servicability is a little skewed.  While MBMA does publish servicability guidelines, they are identical to what is published in AISC Design Guide 3.

On a daily basis I deal with buildings that have changed ownership and the current occupant needs to support an RTU, exhaust hood, mezzanine, etc.  We do expect to get paid for this analysis and specifying of any re-enforcing scheme, but I think that anyone expects to be paid for services outside the scope of the original Contract.  Many times it does take significant field work to install the re-enforcement and if that is the case I warn the customer that it may not be feasible to attempt the modification.

It seems a little like a witch hunt here.  Multiple structural failures, comparing PEMB to a gas station canopy, and having a structural failure that the most likely cause is due to modification without approval or analysis from the PEMB supplier?  Is there an axe to grind with the PEMB Industry, because as mentioned above these are no longer off the shelf buildings.  Each building is designed per Code and the Contract Documents.

 

RE: metal building versus conventional steel framing

Welcome to Eng-Tips, audeuce02.  271828 needs all the help he can get.  

RE: metal building versus conventional steel framing

What minor modification could be made to a MB column that would cause catastrophic failure?  I reviewed a building were the someone had put a window in the wall sheeting (in this case bracing), the window was for a toilet (1 sqaure foot). The building fell down in the next puff of wind.

"Each building is designed per Code and the Contract Documents" would you like to bet your house on that.
 

Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that them like it

RE: metal building versus conventional steel framing

I missed the "column" (the most important part)part when i red the sentence, sorry.

Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that them like it

RE: metal building versus conventional steel framing

"271828 needs all the help he can get."

LOL, I thought I was doing pretty well for 1 against 5!

RE: metal building versus conventional steel framing

No doubt about that, 271828.  I just thought you might be getting a bit tired, and audeuce02 as a first timer sounds like he might be able to pick up some of the load.   

RE: metal building versus conventional steel framing

I'm more tired of the ASD vs LRFD debate.  It's almost 2010, far too late for highly educated professionals to still be complaining about it, IMO.

This thread reminds me of my own disdain for MEs on bldg projects.  They always seem to be behind and get a lot more fee/work.  However, the truth is that I don't know enough about what they do to validly complain about them.  Being human, I do it anyway, ha ha.

RE: metal building versus conventional steel framing

"Each building is designed per Code and the Contract Documents" would you like to bet your house on that.


I would bet my house any day on that statement for buildings that are designed by me.  Contract Documents is a very broad term.  There are many times that the Contractor does not provide the PEMB the plans and/or the specifications that have been generated by the A/E.  As a PEMB supplier we provide a detailed Contract as to what we are providing, including all Code and Servicability issues being noted.  The issue here is not really with PEMB, but with Contractors and end customers looking to start a project and then when it comes in well over budget, they shop it out to PEMB for cost savings.  We look for opportunites such as lowering drift criteria from the H/600 as required by the BIA to H/200 for reinforced masonry walls and L/240 for masonry walls.  Are we providing a substandard design or not following the requirements of the Codes when we use the lower requirements that are suggested by AISC?  I am a Structural Engineer just like many of you, and do not appreciate the implications that my designs are substandard.  Especially when it gets to the level of questioning public safety.


Modifications to any structure without guidance from a competent Engineer have potential for failure, please do not pigeon hole an industry.


And to 271828, there is no need to discuss ASD/LRFD or Ninth Edition/Thirteenth Edition.  We all know that the Ninth Edition is the holy grail and all other manual should be discarded immediately.

 

RE: metal building versus conventional steel framing

I reviewed a building were the someone had put a window in the wall sheeting (in this case bracing), the window was for a toilet (1 sqaure foot). The building fell down in the next puff of wind.


I would like to see some of your findings on this.  I only rely on sheeting diaphram action for transverse bracing of smaller endwall frames.  I would think that there are previous modifcations prior to the removal of the 1 square foot of sheeting that caused the failure of the diaphragm.  If you see one of the buildings that I design, you will clearly see on the drawings the amount of panel that must remain undisturbed along with the note to not add openings without first verifying the adequacy.

RE: metal building versus conventional steel framing

PEMB guys should find another site. Their stock buildings drive me nuts. If it is not made out of a MINIMUM W14x90 Columns and W30x90 Beams it is junk.
HAHAHA
Just kidding Audeuce02!!

RE: metal building versus conventional steel framing

I reviewed a building were the someone had put a window in the wall sheeting (in this case bracing), the window was for a toilet (1 sqaure foot). The building fell down in the next puff of wind.


If this piece of sheathing really was the cause of this infamous collapse the building was designed by an idiot to begin with. Having said that, this is complete BS. It must have been one bad-ass wolf huff-puff-puffing and blowing the house down or and F5 tornado.
 

RE: metal building versus conventional steel framing

I assume that the story of 12" cut over a toilet is a joke.  No way that could be true unless the 12" took out the x-bracing and there was no other x-bracing or sidewall sheathing.

RE: metal building versus conventional steel framing

maybe they cut the hole in the wall for perverted reasons or so they could shit directly out thru the wall and cut back on water costs.  

RE: metal building versus conventional steel framing

Makes sense, except that the hole is above the toilet.  Maybe it's like monkeys flinging poo at the zoo.

RE: metal building versus conventional steel framing

I dind't even consider it being a "glory hole".  That would cause a failure in any building.

RE: metal building versus conventional steel framing

"And to 271828, there is no need to discuss ASD/LRFD or Ninth Edition/Thirteenth Edition.  We all know that the Ninth Edition is the holy grail and all other manual should be discarded immediately."

I'm assuming that you guys are using the 13th Ed. by now.  Have you noticed a difference in economy of your frames?

RE: metal building versus conventional steel framing

No Joke here people, The sheeting was the only bracing, no x-bracing,nothing else. The sheeting in question was 5ft long and inbetween roller doors. I concluded that this is were the sheeting first failed, ripping at fist leading to a dominate opening leading to the complete collapse, I find these reports hard to find a 100% confidence that this was the failure point, and you could argue that i got it wrong and it was the roller doors, but the sheeting was ripped from the windows corner, thus my conclusion. I would agree that the designer was an "idiot" (can't post parts of the report because I sure i would get my ass kicked). He has since been disciplined by the local authority for other designs. But he is the certifying engineer for a lot of PEMB in my local area.

The cyclone was not a design event, it was close though. JCU did a review of the event and there a short version of the report is below. I can post the complete report if you like. I make have stretched the truth when i said puff of wind.

http://www.jcu.edu.au/cts/idc/groups/public/documents/newsletter/jcuprd_045826.pdf

You will see there are critical of sheds, but not just PEMB (but most of the sheds were PEMB but again not all). The main problem was roller doors I believe, they are not designed well, and most engineers in the shed industry including PEMB use minimal internal pressure and when the roller doors fail due to incorrectly designed mullions or wind locks the building disappears.

audeuce02,
I was not inplying that your designs are below standard, my apologizes that if it came across that way. I was just trying to point out while everyone on this forum may have ethics ect, saying everyone dose is a stretch. I would accept that you design your building correctly and i wouldn't bet my house against your design not meeting the codes, but I would happily bet my house against there being a few shed manufacturers (PEMB) in my local area that design well below the codes. The Deflection criteria that your reduce doesn't worry me, this is a case by case situation and if you are happy to reduce by all means do so.

"If you see one of the buildings that I design, you will clearly see on the drawings the amount of panel that must remain undisturbed along with the note to not add openings without first verifying the adequacy". This is another problem with the local industry, there is no requirement for this to be shown on the drawings, in other countries there is a requirement to show this and display a sign, alas not the case here. We also have problem with this type of bracing being used in cyclone regions were sheeting fatigue and sheeting design has not been tested.  

Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that them like it

RE: metal building versus conventional steel framing

271828...
1 against 5... we weren't trying that hard! <G>, but, you did OK...

I like the engineering that goes into a PEMB... I once had a prof tell me that if a civil engineer designed an aeroplane, it wouldn't get off the ground. PEMB engineers are trying to change that...

You can see from my posts that I have encountered a few problems and have incorporated many of these in my standard drawing notes...

From CSSBI spec...

"Building load resisting frames: lateral drift
shall not exceed [1/60][1/80] [1/100]
[1/300] of the height measured at the
eave, under wind loads or applicable
lateral cranes loads.
SPEC NOTE: A deflection limit of 1/300
may be required for the proper
functioning of cranes or to prevent
damage to brittle finishes such as brick
and glass.
.2 Roof framing: [1/180] [1/240] of the clear
span under full specified roof live load.
.3 Wall Cladding and girts: [1/180] of the
clear span under full specified wind
effects."

Elsewhere in my drawing notes, I specify deflections:
I've never used L/60 for anything...
LL is L/240 and combined DL&LL L/180...
Combined girts and cladding L/240; the wording will be tightened up to ensure the integrity of the envelope. I also tie this in to masonry stuff, now as a result of problem experienced a few years ago...

I also have a standard letter for the owner to sign off on any changes to the assumed loading and deflection criteria.

Two added items as a result of this thread... The PEMB engineer will be responsible for the design, fabrication and ERECTION of the building.  Also, the integrity of the skin is paramount in using lower design wind pressures; I'm not sure how to address that, just yet...

Don't feel too bad, though, my standard drawing notes file is in excess of 200K text file and PEMB are only a small part. They have been assembled from 40 years of 'things'.

As Hokie noted, welcome audeuce02... look forward to your comments on other issues...

Dik

RE: metal building versus conventional steel framing

271828, the Black Book is the devil but we are now using it.  We have found a little economy in 13th versus 9th Edition, but it is not what I would consider substantial.

Rowingengineer,  Do you think that it is possible that the doors actually blew out first causing a significant increase in internal pressure?  I am not sure if I would say it is the second highest cause, but failure of the doors to be designed for equal or greater than the C&C pressure does cause significant issues.

I think the term PEMB is vague and often misused.  MBMA actually no longer refers to PEMB, but we are now Engineered Building Systems.  I think that PEMB may be getting a little bit of bad wrap from some of the back yard type frame shops that are not providing a truly designed structure.  These fall into the realm of what I call "blow away buildings".  There is a lot of truth in you get what you pay for.  That is why MBMA developed the AISC MB Quality Program and now has IAS AC472, to insure that Engineering and Manufacturing processes are in line with industry and Code approved standards.
 

RE: metal building versus conventional steel framing

Just to clarify, the buildings and the event that Rowingengineer described were in Queensland, Australia.  As far as I know, we don't really have a PEMB industry in Australia similar to the North American version.  What we do have are a lot of 'sheds' built with cold formed sections, and these have a lots of problems in a cyclone.  There are some Armco buildings around from previous times, and I don't know that there has been a particular issue with these.  We also have a lot of old 'sheds' built with pipe fabricated into trussed columns and rafters, and most of these are hard to justify.

RE: metal building versus conventional steel framing

Hokie
Are you saying I am talking apples while everyone else is talking oranges?
 

Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that them like it

RE: metal building versus conventional steel framing

Actually, RE, I thought you might have been talking bananas.:)

RE: metal building versus conventional steel framing

"271828, the Black Book is the devil but we are now using it.  We have found a little economy in 13th versus 9th Edition, but it is not what I would consider substantial."

I think you'll like it over time.  Just takes getting used to like anything else.  I bet you guys hated losing whichever model bldg code you were using in 2000 and switching to IBC also, right?  I know that's the way I felt.  A little while later, I coudln't even remember why I cared that I lost teh SBC.

"A little economy"?  Do you think it's like a percent of frame weight?  I remember years ago working on a MB R&D project in which our program did a little better job optimizing the splice locations.  We ran a simulation of tens of thousands of frames of different configurations and loads.  They came out something like 2% lighter and people thought that was a pretty big deal.  MB R&D is the most fun type of engineerng that I've ever done.  I don't think I'd like to design them, though.  Program does a lot of work.

RE: metal building versus conventional steel framing

"A little economy"?  Do you think it's like a percent of frame weight?

I am glad you asked that question, because it made me run some numbers.  I recant my previous statement, it is a substantial cost savings.  On average we are seeing a little better than 4% weight savings over ASD.  4% weight savings when 40% of the weight is primary framing, and material cost as a percentage of sales is 55-62% is a heck of a lot more significant than I had previously thought.

The real problem in the PEMB market in the US is that you have Sales reps that are not knowledgable of the product limitations that are communicating with A/E Groups and overcommiting to what we can provide and how we can frame it.  There are many times that I scratch my head an question exactly what the hell they are thinking.

RE: metal building versus conventional steel framing

I love it when owners buy a PEMB and then try to put some cute little haunches on the columns and put a crane runway in it. hahah
We have been called to do runway surveys and the whole freaking building was racked and tweaked to hell in back and the crane was binding up and jumping the rails.  

RE: metal building versus conventional steel framing

I also love those cute little cable braces they use....those are really neat (just kidding)

RE: metal building versus conventional steel framing

4%!  That's very cool.  Somebody needs to write an article about it.

Are you guys using hte Direct Analysis Method or the Effective Length Method?

RE: metal building versus conventional steel framing

audeuce02,

I think it's hilarious that you are just now using the "black" book.  It's been adopted for at least 3 years.  If you're in Cali, then I won't knock you.

RE is correct, I worked in the Texas/Oklahoma/Missouri/Louisiana markets where it's much more competitive than the west coast markets in regards to conventional vs. pemb marketing.  The one thing that is lacking in the pemb markets was just touched on and that is this:  the "salesmen" that sell these products do not know a lick about engineering and they pretend to know.  In my first 8 years of engineering, I saw it at 3 different pemb companies ranging from 20 employees to 400 employees.  It's not right, and gives the industry a bad name.  Most of their engineers are decent if they've not become too dependent on their proprietary (or MBS) software.  The software allows the pemb to "turn the brain off" and trust the output - a very bad climate to be in as a marketable engineer.

RE: metal building versus conventional steel framing

We have been using 13th Edition on everything IBC 06 since adoption.  It's just that I still find myself wanting to look for my 9th Edition when I need to reference something.  

Software dependence is a bad deal.  There are many PEMB Engineers out there that don't really understand what the software is doing or what they are truly trying to accomplish with their design.  I have trained multiple engineers and also quite a few estimators.  If they cannot draw the free body diagram and show the load path, I know that I have my work cut out for me.  Basic load path and load application is something that many people have a hard time with.

RE: metal building versus conventional steel framing

Getting back to the metal building deflection discussion... several posts indicate that the engineer of record should specify deflection criteria to be used in the design of the mental building structure. I've done it myself on numerous occasions, but I'm now questioning whether or not that is a good idea. By specifying deflection criteria, you are basically letting the metal building guy off the hook. If there's ever any kind of a problem, say with the operation of a crane, they can simply claim that they designed in accordance with the engineer's criteria, and it's the criteria that is at fault. Any thoughts?

RE: metal building versus conventional steel framing

OOPS! Didn't mean to call it a "mental" building.

RE: metal building versus conventional steel framing

If you don't specify anything, knowing that the PEMB requirements are beyond the crane allowables, you're going to be in even more trouble.  
In other words, if you know something about the design and don't pass it on to the component (PEMB) designer, that borders on negligence and the lawyers are going to have a good time with you.

RE: metal building versus conventional steel framing

Undoubtedly some of your experiences with PEMB has been with piss poor comapnies to say the least.  The issue of deflection/servicability is being completely misunderstood for the PEMB companies that are MBMA/AISC MB/IAS AC 472.  We meet or exceed the published servicalbility criteria in the Metal Building Systems Manual Section III.  In reality, the information in this section comes directly from AISC Design Guide 3.  

If you have had a compnay provide a building with a crane and H/60 eave drift, they are not following any of the industry guidelines.  And in reality, I would consider this criminally negligent due to the bridge having potential to actually jump track due to the frame displacement.

RE: metal building versus conventional steel framing

audeuce02,

I don't have a copy of the AISC Design Guide 3. Would it be possible for you to post the deflection requirements from that guide, particularly related to cranes and CMU walls? Thanks.

RE: metal building versus conventional steel framing

Thanks, audeuce02... I take back almost everything bad I've ever said about PEMB engineers! HA!(If you didn't catch it earlier, I was one myself for about five years with dear ol' Butler)

RE: metal building versus conventional steel framing

Everybody should try it for a little while.  You have to be creative to bring some of the commitments that the completely uneducated sales staff to reality.  I am to the point that if I here one more "I didn't think that note was important", or "that does really apply, does it, my head is going to explode.

Which Butler office did you work at.  I spent a little time with Liberty, the Butler offshoot.

RE: metal building versus conventional steel framing

I worked for Bulter in their corporate office in Kansas City, MO (we're talking the '70s here).

I always felt we were a pretty creative group. Back then, Butler had a three-dimensional roof and floor truss system called Space Grid, a geodesic dome system, and a truss main frame sytem that used neoprene pads in the truss bottom chord-to-column connection to reduce gravity load bending effects on the columns... some pretty innovative stuff!

RE: metal building versus conventional steel framing

One of the boys in the Ivory Tower.  The Delta Joist is and was a slick system, but I believe they have stopped offering it.  Panelizing the roof on the ground significantly sped erection and lowered cost in the field.

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