Pricing a cantilever

philliosmaximus

philliosmaximus

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Iam in the process's of pricing a good size job , one section 35 meters long is to be an independent cantilevered from the ground to first floor with 6 working lifts on it , there is enough room to build as bigger horse as we need to , my problem is how to price it before its designed anyone have any ideas as how best to tackle this as iam scratching my head here :unsure:
 
Thats the point exactly HSWT very easy to underprice , i see it as ladder or unit beams horsed out and up , but god only nows how many . Recent project we had a designer insisting on X beams for a bridge that was 10 meters long and 7 working lifts on it.
Never considered RSJs as an option , would they tend to go in at 2 meter centers or there abouts ?
 
Depends on the section size you're willing to go to but 6mc/c is not uncommon. Did a similar job using 203 UC 86s @ 4mc/c with unit beams spanning between. This was carrying a basic 4+2 (2m lifts, 2m bays) but they'll need to be about 6m long to counter the uplift.

Would your regular Engineer be willing to knock you up a quick couple of options (one beam horse and the equivalent steel option) to give you a rough area to look at?
 
He would normally Nick , but he is very busy rebuilding the Falklands airport at the moment strange as that sounds and i have had to use a new engineer who is proving very slow to even answer an email
 
I the cantilever coming out of the ground floor windows or do you have the option of locally removing brickwork/glazing/whatever? If it is out of the windows then this pretty much governs the centres and the amount of beams/steels to be used.

Without more info it's hard to give a decent opinion but I understand you're not going to want to go into full details on the internet.
 
Nick the ground floor windows are large 2.4m long and will be taken out so centers will be pretty much what we need , if we where to use unit beams , with a boxed unit beam bridge sitting on top and the scaffold taken up from there 6 fully boarded lifts, what would the centers of the unit beam needles need to be , and approx how far back would the horse need to go , i personally would work on 3rds , horse 3 x the scaffold so i would probably erect a 6 meter horse inside with 4 jacked standards to each needle , thats what i would do in the days before needing designs
 
SUMMARY said:
Beam Length 6.00 m
Moment of Inertia 10572.00 cm4
Elastic Modulus 206000 N/mm2

APPLIED LOADING

Point Loads
8.65 kN .... at 0.00 m
9.45 kN .... at 1.00 m

REACTIONS (+ve Up)
24.79 kN .... at 2.00 m
-6.69 kN .... at 6.00 m

MAXIMUM LOADS & DEFLECTIONS
Max. Reaction 24.79 kN .... at 2.000 m
Max. Hog BM 26.75 kN.m .... at 2.000 m<27.7kNm
Max. Shear Force 18.10 kN .... at 1.000 m>15.6kN
Max. Sag Deflection 4.70 mm .... at 0.000 m
Max. Hog Deflection 1.26 mm .... at 3.700 m
Click to expand...
I based this on 2m c/c just to make it a bit quicker for myself (sorry). You would be looking in the region of twin units or single X beams @ 2m c/c.

This is a complete guestamate. I also went for your 6m horse so as you can see the uplift is not excessive.

Caveat emptor though. This should give you a good idea where you want to go for first knockings but I would really be bashing down your designers door for a full and safe scheme.
 
We only use T/F HSWT but below is the pavement so we cant spur anything on the ground floor level

Thank you Nick that is really helpful mate ;)

---------- Post added at 03:58 PM ---------- Previous post was at 03:57 PM ----------
Havespannerwilltravel said:
I would generally only use steel beams if they were on the slab. If going through windows why not a T&F truss out?
Click to expand...
Sorry HSWT the beams will need to be at the underside of the slab , and not sitting on the floor
 
No worries Phillio. Once you get a proper design going you may find that the quantities can come down a bit but I wanted to lean a bit towards the heavy side for "worst case".
 
Been in touch with Ben from 48.3 and looks like double line unit beam needles and a unit beam bridge sitting on the needles.
Thanks for the advice Nick you where spot on with it ;)
 
Glad to help and you're in good hands with Ben, he's a good Engineer. Good luck with job mate.


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