metal building versus conventional steel framing

[archeng59]

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.

 

[hokie66]

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.

 

[271828]

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.

 

[audeuce02]

"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.

 

[audeuce02]

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.

 

[Stillerz]

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!!

 

[Stillerz]

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.

 

[271828]

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.

 

[Stillerz]

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.

 

[271828]

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

 

[audeuce02]

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

 

[271828]

"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?

 

[rowingengineer]

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

 

[dik]

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

 

[audeuce02]

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.

 

[hokie66]

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.

 

[rowingengineer]

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

 

[hokie66]

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

 

[271828]

"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.

 

[audeuce02]

"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.

 

[Stillerz]

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.