Canopy using steel hollow sections?Advice please.


I want to build a canopy on the pine end of my brick bungalow. I need it to be 10Metres long, and 4M deep, and covered with twinwall polycarbonate, however, I would like it to be a light structure (minimal CSA) so as to minimise interference with the view of the garden and beyond, so I'm thinking to use 3 or (4 at a maximum) upright supports, and a gutter beam which is not too deep. I'm minded to use steel rectangular hollow sections for the construction, cut to size, welding brackets or plates at appropriate joining points and having the whole lot hot galvanized before assembling on site using ss bolts.
My gut instinct is to use 50mm square tube for the uprights and concreted into the ground. 50mm square tube for the rafters (4M long @ 1M centres) 150x50 square tube for the gutter beam, supported by the vertical members to give 3.3M spans, (rafters providing lateral support).
Stability would be provided as one end of the canopy would be built into a corner formed by the bungalow and an attached garage projecting 4M proud of the pine end, I have no experience of using this material beyond building a 1 ton trailer using 50mm square steel tube welded to form the structural chassis.
I understand that planning permission would not be required for this construction, however I would be inclined to use the services of a structural engineer to check and modify the proposed design as necessary. I would imagine that the structural calculations would be minimal for such a simple structure, however it is difficult to locate a structural engineer having the appropriate experience for this project. I'm located in N Shropshire.
Advice and/or constructive criticism welcomed.
Thanks in anticipation. Tom Williams
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Mary

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Mary Fisher wrote:

Shouldn't that be spouse.fisher@... :-)
Owain
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Much obliged Mary, have emailed him for info.
Thanks Tom
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I don't think he'd see it until this evening and we go away tomorrow for a few days so I'll make sure he looks.
Mary
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My "gut instinct" says that 50mm SHS would be seriously overspecified for this. You could go a lot smaller if you wanted.
Christian.
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Rather keep a wide section, for rigidity, and take the lightest gauge practical [get advice from a specialist contractor] Practical issues will include, for instance, the warping of very light section when hot-dip galvanized...
-- R'zenboom
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It doesn't need to be galvanised.
Mary

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maybe...if you don't mind the time and effort to strip epoxy and recoat every few years...
-- R'zenboom
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No-one mentioned epoxy.

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Maybe!! however it would depend on the thickness of the walls of the tube and with an upright approx 2.3 M high, a wind gust imposing a compressive load might cause it to collapse, whereas it would be perfectly stable under a similar tensile force. We tend to get gusty conditions in the proposed location. Cheers Tom
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Look uo or down most streets these days and you will see all kinds of framed canopies implemented by retailers and merchants. Why not talk to a couple of companies that design and build signs? They can help you understand wind loading, bracing, connectors, weldments and so on and most especially recommend a reliable manner to attach to another structure if the final design requires doing so.
<%= Clinton Gallagher METROmilwaukee (sm) "A Regional Information Service" NET csgallagher AT metromilwaukee.com URL http://metromilwaukee.com / URL http://clintongallagher.metromilwaukee.com /

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8<

If its any help my car port is 9.5m x 4m supported on 5 50mm poles. It has a wood (150x38) beam along the poles and eight of the same from the wall cap to the pole cap.
It has been there for 24 years through rain, storm, snow, etc.
My neighbour is a structural engineer and he said it more than strong enough.
50x50 mm steel is probably overkill but its cheap. I would think that the 150x50 is well OTT.
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