Bolts anchored in concrete
Bolts anchored in concrete
(OP)
OK, i am not sure how to approach this problem. I dont have all of the details yet:
I have four 10" bolts anchored in concrete about 8" deep in a 5" square pattern. I will have a 1/2" steel plate with a 15 ft 4 1/2" sch. 40 pole welded to the center of the steel plate. Some minor equipment will be installed on top of this pole.
I am assuming that the bond from the concrete to the steel bolts is the weak link and if enought force is applied that it will rip the bolt from the concrete. I want to find out that max force. Some tip on what calculations to use and how to go about this would be appreciated.
thank you!
I have four 10" bolts anchored in concrete about 8" deep in a 5" square pattern. I will have a 1/2" steel plate with a 15 ft 4 1/2" sch. 40 pole welded to the center of the steel plate. Some minor equipment will be installed on top of this pole.
I am assuming that the bond from the concrete to the steel bolts is the weak link and if enought force is applied that it will rip the bolt from the concrete. I want to find out that max force. Some tip on what calculations to use and how to go about this would be appreciated.
thank you!





RE: Bolts anchored in concrete
RE: Bolts anchored in concrete
TTFN
RE: Bolts anchored in concrete
Dik
RE: Bolts anchored in concrete
TTFN
RE: Bolts anchored in concrete
RE: Bolts anchored in concrete
The concrete is bascially a big weight to keep the pipe and the equipment mounted from tipping over for any reason. the 4 bolts are set in concrete and a 1/2" steel plate is attached to the bolts and then tightened down with some washers on each side and then the nut.
the steel plate has a 4 1/2" diameter sch 40 steel pole that is 15 ft. long welded to the plate. I just need to make sure, in the event of high winds or if it gets backed into, etc.., that it will not either snap the bolts or rip the bolts out of the concrete, or what kind of force to expect for the bolts or concrete to fail.
dik: 1/2" bolt I will check out the AISc, if you have a quick link, i would be grateful.
Arto: if you can giveme reference to the "breakout cone" strength, i would appreciate it!
IRstuff: Bolts will hold down the plate that has the pole and equiment attached. have not read the discussion on the big dig
basically, how will I verify that this will not tumble in high winds or generate a rough figure of how much lateral force it will take to fail the bolts or the concrete.
I hope this is clear enough for you guys, sorry if it is not!
thanks in advance for all your time!!
RE: Bolts anchored in concrete
used on monopoles. Monopole design url.
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RE: Bolts anchored in concrete
I'm sure we can try to help you all day long by pointing you in the right direction but we can't actually do the work or run the numbers for you.
RE: Bolts anchored in concrete
Dik
RE: Bolts anchored in concrete
I am currently trying to develope a spread sheet to help me with the design of base plate connections for communication monopoles and this is how I normally check the bolts that we are planning to use
RE: Bolts anchored in concrete
With a 100 mph wind, wind pressure is 25.6 lb/ sq.ft..
Wind and gust(30% extra) creates a 33.28 lb/sq.ft.
Projected surface area of pole is 15'* 4.5/12= .277 sq.ft.
Total wind load 33.28 * .277= 9.24 lbs.
Moment on base of pole is 9.24*15/2=69.33 ft-lb
Now here is the clincher: since there is no contact between base plate and concrete pad from my original premise, load from the moment is taken by your bolts. One set of bolts will be in compression and the other set in tension.
The set in tension will be designated as 2T and must resist the moment at a leverage arm of 5". the value of T
is equal to 69.33 * 2 * 5= 83.2 lbs for one of the bolts.
It become obvious that the 1/2" plate and 3/4" bolts are oversized by now but will stay with what you got.
For length of embedment of bolts in tension and compression should not be less than 12". From concrete formulae the bolts in tension have this for Ld= (.04or.04)*Dd*Fy/(F'c)^.5. .04 or .05 is bases on size of bolts or rod, Dd is dia. of bolt or rod, Fy is tensile strength of steel, and F'c is compressive strength of concrete.
Since base plate and bolts or threaded rods are well oversized, stay at a 12" of embedment but with bolts or rods make sure that you have a nut or J hook at the ends embedded in the concrete.
RE: Bolts anchored in concrete
I would be always concerned about some
minor equipment at the top of the pole
as to its effect on the calculation.
Note that the bolts are 1/2 inch diameter
and the plate is also 1/2 inch thick and
not 3/4 diameter bolts. If 3/4 inch bolt,
then the recommended plate thickness should
also be 3/4 inch. What is the effect of
the moment at the concerete base? Looks
like the base plate and bolts are ok.
Isn't more information required as to the
concrete below the base plate?
RE: Bolts anchored in concrete
RE: Bolts anchored in concrete
UcfSE has the correct procedure and his recommendation of going with a headed rod or nut embedded in the concrete is the current best practice.
RE: Bolts anchored in concrete
These draw presses put one humonogous stress load on the floor when they are running. No problems with the anchors though.
If that doesn't work nothing will work.
RE: Bolts anchored in concrete
I just need to make sure, in the event of high winds or if it gets backed into, etc.., that it will not either snap the bolts or rip the bolts out of the concrete, or what kind of force to expect for the bolts or concrete to fail.
Not certain about the concrete approach as not enough information is given about it.
The bolt formula S = F/A seems appropriate.
A = area = .1419 x 4 bolts = .5636 sq.inches.
This is assuming simple shear at the base of
concrete for the bolts and no moment load.
Nothing is that simple. By rearranging the
above equation, you can get the F (force) required.
S = Stress.
RE: Bolts anchored in concrete
Also, you have the same kind of figuring to do on things like water tanks. You figure the form drag on the object under maximum wind speed assumptions. A flat road sign has plenty of drag.
The taller it is the more bending moment you have. A 4-1/2" square tube that's really long gets rather flimsy. I'd go out and measure a road sign in the range you are thinking about. It should give you a good start.
How large is the "sign" in square feet?
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RE: Bolts anchored in concrete
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RE: Bolts anchored in concrete
1. SIGN STRUCTURES AND FOUNDATIONS: A Guide for Estimators and Designers
2. ENGINEERING SIGN STRUCTURES: An Introduction to Analysis and Design
Each of these books have all the info you will need to calculate the concrete strength and bolts/base plates etc...
Both of these books can be found on www.signweb.com or www.amazon.com
Don't worry about people stealing your ideas. If your ideas are any good, you'll have to ram them down people's throats.
--Howard Aiken, IBM engineer
RE: Bolts anchored in concrete
Dimjim- I missed my typo error on the tension side of bolts; expression s/b 69.33*12/10=83.2 lbs.per bolt.
In so far as shear at the base it is not a significant value to determine resultant stresses.
The only thing missing is the projected area of the object on top of pole. Weight of top of pole also appear insignificant.
With regard to length of embedment on the tension side=
.04*.5*36000/(5000)^.5=10.2" per bolt. You may redo this calculation for different steels and concrete strengths. Also allow 3" clearance between concrete base bottom and ends of bolts.
RE: Bolts anchored in concrete
Mike Halloran
Pembroke Pines, FL, USA
RE: Bolts anchored in concrete
Can I borrow your quote? Howard will be a famous man.
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RE: Bolts anchored in concrete
Feel free to the quote.
Don't worry about people stealing your ideas. If your ideas are any good, you'll have to ram them down people's throats.
--Howard Aiken, IBM engineer
RE: Bolts anchored in concrete
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RE: Bolts anchored in concrete
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RE: Bolts anchored in concrete
My results have been pretty consistent with problems associated with anchoring shelving to warehouse floors, that sort of thing.
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: Bolts anchored in concrete
Interesting topic with great replies!