Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

re: bar spacing

[Subject Prev][Subject Next][Thread Prev][Thread Next]

Jeff,

Great question, couple years ago we had a big argument with a GC who said he could form and pour walls on a maybe 5000sf single-story retail building cheaper than doing CMU. The client wanted more “wind resistance” so he was sold, and we said sure, concrete formed walls may be better than CMU for that. Although, the wood trusses would still be the achiles heel and windows getting blown out, etc., but that was not worth getting into. We redesigned it at 18” o.c. because of course the calcs did not require anything more than that. The GC flipped out because “his other engineer” always does 24” o.c., we copied the section of ACI that limits the spacing and sent it to him and the owner/client. He was still not convinced, but we did not know other sections of code may apply. Now I think his other engineer maybe got away with it for residential ICF and other applications and was then applying it to a commercial job. They switched back to CMU.

 

I cannot believe in our instance or your instance that 33% more rebar makes THAT big of a deal. Not when you consider all of the interior finishes, MEP, site work, and all the other costs. Jeff, for your building I did a quick calc and say your house is about 2400sf at 60’x40’, it would mean about 33 more vertical bars. Bars are not that expensive, and labor to put them in a wall cannot be THAT much more. Say it is liberally $30 per vertical bar, that is $1000… For a large increase in strength (admittedly probably way over design loads in an area with little wind but you have some big seismic I think), but moreso, a nice additional amount of crack control. I would assume the finish in Nevada on concrete would be stucco. Stucco and paint is quite expensive, and repairing hairline or other cracks in stucco quite expensive and ugly. Doing forensics I see a LOT of expensive houses with lots of settlement cracks, albeit, mostly in CMU. I would attempt via a quick phone call to inform the owner of the ADDED VALUE of the additional reinforcement. Probably spending more than that on tile in one bathroom.

 

ADDED VALUE is a hard sell these days in America’s Wal-Mart, more-is-better, made in China culture. Very few things are seen as worth more money if you can get it cheaper somewhere else. Structural engineering services are one of them that are a hard sell as we can bring ADDED VALUE to any project, but most clients do not realize that (in part because we don’t tell them). Much easier for an architect with fancy elevations and pictures of his past buildings to sell the creativity and flare of his abilities, where as we are viewed as utilitarians who go by the book and code and produce a uniform design no matter who we are. If you tore your ACL would you go in the yellow pages and call around for the cheapest guy? If you needed a root canal would you go to some trailer in the woods because it is cheap? Besides maybe cars, furniture, sometimes clothing, and kitchen finishes, Americans are not connoisseurs of real quality products. Even houses- the public has no clue if the foundation, walls, trusses and connections are done correctly and could care less. Hey, it was built to code, must be OK. They want high ceilings, fancy cabinets, hardwood floors, and granite throughout. I see just as many problems with $500k++ homes as every day, older ranch homes.

 

Maybe one area we are making a resurgence in is beer. For far too long they let us eat cake- Budweiser, Michelob, Coors, is there any difference in their watered-down lagerish taste? Hardly. Now, in part to Sam Adams leading the charge, there are thousands of micro brews creating a fascinating and delicious array of complex tasting beers right here in the US. You SHOULD pay a couple bucks more for a good six pack, it is worth it, life is too short to drink crappy cheap beer. (I will say on a hot summer day while doing yard work in Florida I do drink cheap light beer, guilty. Guess that makes me a flip flopper.)

 

Sorry, bit off topic.

 

Andrew Kester, PE

Orlando, FL