Any structural engineers on here

[dbz864]

I think that's who i need! Im going to build a steel structure that needs to hold about 3 ton, im currently trying to work out the costs etc. I need some advice on what thickness steel box section and "spans" etc. to make the base out of? Any good advice on here?. I can take a educated guess but dont want to "over or under engineer it" Many thanks Adam

[a1winchester]

I would need some idea what it's for, what height, width, length etc. Is it a hoist? Mobile or fixed? How many legs?

Once answered we can move forward with a design.

[dbz864]

Hi thanks for the reply. Basically i'm hoping to build a garage in the shape of an airstrem caravan, my plan is to have a steel frame base, ideally something i could bolt together to make it easier to erect at my house(probably galvanised) which will be sat on short adjustable legs these will sit on a old concrete garage base. The upper frame i was going to make out of steel box section, which will be bent in a arch shape, the 4 corners are curved and are double curvature in shape. The outer skin will be aluminium sheet in between the outer and inner skin will be insulation to hopefully stop condensation. There will be a few side windows, a side door and a large opening front door which would be hinged off one of the arch shaped box section which would be big enough to drive a car in, tho i cant imagine me every putting a car in.
length 5750mm x 2950mm x height approx 2400mm. I've made a few rough plans but need some advice on the size of box section for the base and side frames, i've got some sizes in mind but i don't want to over engineer it with over the top frame work. Im not to sure about insulating it (how thick)which is a factor when choosing the upper frame box section (depth) .
Can you help in any way. Thanks adam

[Smosh]

I'm not an Engineer, just a Technician for a Structural Engineering firm, but, I'm happy to help out where I can.

I'm struggling a little to visualise how you intend to build it.

Personally, I would think the best thing would be to fabricate a number of frames - either use cleats to from the shape of the outside, or get some box section rolled and welded to form the shape.
[img][IMG]http://i258.photobucket.com/albums/hh250/joshs1988/Capture.png[/img][/img]

I would then fix these directly to the existing slab (assuming slab is suitable). You would need to consider bracing to prevent these from racking though.

atb,
Josh

[a1winchester]

Not sure I would insulate as the inside temperature is going to equal the outside temperature a lot of the time unless there's some form of (dry) heating.
If you've got a decent roof slope, any condensation will run down and not drip.

What you are describing (if my imagination is correct) is a mini Nissen Hut with curved ends. But as the height more or less equals the width, the profile is half an elipse, not half a circle.

You mention in the o.p. that it has to support 3 tonnes. Is that a hoist load or what? Without that load, you can construct the thing with just curved profiled cladding. Wikepedia gives the sizes of timbers used. Very lightweight, so you are right to be cautious not to over engineer the thing.

[dbz864]

Thanks for the replies. Had to look what a nissan hut is! i know them as air raid shelters. lol. I will try to explain briefly what i want to do. Basicly its going to be a garage at my house. I want it sat on a steel box section framework which is sat on adjustable legs. I need the frame work to support the weight of a car and other bits as well as the outer skin of the garage so i thought if i had it made strong enough to "take 3 ton" that would be ok. Not to sure what you meant about the condensation, i thought it would get a lot if it was say icey out side, i didnt plan on having it heated, my only experience of this was i rented a storage container (old van body) and that suffered terrible with it,but was single skin. My main question is the base frame work (the part thats going to have a car sat on it) im unsure what size box section to have it made out of? The other question is the size of box section or C section to have the arches made out of, the size of that will make the void where the insulation would go if i need any? THis has probably confused you more. thanks any thoughts or advice would be ace.adam

[dbz864]

I'm not an Engineer, just a Technician for a Structural Engineering firm, but, I'm happy to help out where I can.

I'm struggling a little to visualise how you intend to build it.

Personally, I would think the best thing would be to fabricate a number of frames - either use cleats to from the shape of the outside, or get some box section rolled and welded to form the shape.
[img][IMG]http://i258.photobucket.com/albums/hh250/joshs1988/Capture.png[/img][/img]

I would then fix these directly to the existing slab (assuming slab is suitable). You would need to consider bracing to prevent these from racking though.

atb,
Josh

thanks for replying .The link is a very similar profile /shape that i want, what you describe is similar to how i have it in my mind to build it, its the sizes of the steel sections im unsure of. Hope that makes sense. Thanks adam

[Smosh]

I want it sat on a steel box section framework which is sat on adjustable legs.

Adam, why does it need to sit on adjustable legs / box section, and can not be built off the existing slab?

[dbz864]

I want it sat on a steel box section framework which is sat on adjustable legs.

Adam, why does it need to sit on adjustable legs / box section, and can not be built off the existing slab?

I need it off the ground as i want it to look like a "airstream caravan" so it will look like its "floating" as if it was sat on wheels, does that make sense?

[Smosh]

Yea, but that would mean it's a ramp up into it?

Depending on how high you want it, you could achieve a similar look by cleating the cladding off rails. Alternatively, building the frame off of stub sections would allow it to appear elevelated. However,
depending on the surrounding area it may create a similar effect or at least a more economical one.

[dbz864]

Hi, not sure what you mean by " cleating the rails" and "building the frame of stub sections" . nice picture by the way

[Smosh]

Normally, when you build something with a frame and cladding, you would put horizontal rails or battens to fix the cladding to between the main structure. rather than fixing these rails directly to the main structure you could offset them by fixing brackets between the rail and the structure. This would allow a square structure, but curved walls if you used different sized brackets.

Rather than build an entire suspended floor structure, just elevate your frame on some box section for example, and with your cladding away from the main structure you could create the look that it is floating.

[dbz864]

Right see what you mean now, would save money, good to get other peoples ideas, thanks

[marlinowner]

Or build a superstructure onto a s/h flat bed car trailer, get it into position, remove wheels and lower it onto blocks.

[dbz864]

Or build a superstructure onto a s/h flat bed car trailer, get it into position, remove wheels and lower it onto blocks.

thats not a bad idea!