# Forum Home Renovation Stairs, Steps and Ramps  Ramp

## Marc

Is there anyone here able to interpret structural steel load carrying capacity? 
I need to know how much load can a 5 meter long 150x50x5 mm carry. From there I can make adjustments in it's wall thickness either up or down.  
I came across this link but it does not help me. http://www.midaliasteel.com/files/38...T_CF_Small.pdf

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## woodbe

Does this help:  http://www.renovateforum.com/f221/st...-tables-99800/

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## Marc

That is a good link but it is for PFC and universal beams not RHS
This is the product I want to use and need to know loading capacity  http://www.orrconsteel.com.au/austra...ral%20RHS.ashx

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## Gaza

Way back I had to study "structures" you might need to do it old school find out properties of the steel such as bending moment then using formulas add you live and dead load. 
Or pay an engineer to run calc   
Sent from my iPhone using Tapatalk

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## Marc

Yes, Gaza the table in my link gives me all that data yet I forgot all about such calculations. There is bound to be a simple table or calculator.

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## dmac

Finger in the wind here, a 150x50x5 mm box section could take the weight of a car. But if you walked over it it may be springy at 5M between supports.  Can you put a support in the middle ? It wouldn't need to be massive, more a dampener 
PS: I use a 100x50x5mm box section at 4M to lift big things (lathe, 1200kg, Mill 800kg etc) and it hardly moves at all. 
Dave..

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## woodbe

How about this then:  Area Moment of Inertia Section Properties: Rectangle Tube Calculator - Engineers Edge Engineering Calculators 
or this:  http://www.engineersedge.com/beam_be...flection_2.htm

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## Marc

> Finger in the wind here, a 150x50x5 mm box section could take the weight of a car. But if you walked over it it may be springy at 5M between supports.  Can you put a support in the middle ? It wouldn't need to be massive, more a dampener 
> PS: I use a 100x50x5mm box section at 4M to lift big things (lathe, 1200kg, Mill 800kg etc) and it hardly moves at all. 
> Dave..

  I can't have a support in the middle since it is over water and goes up and down with the tide. What I can do is build a handrail that acts as a beam to stop flection.  
The maximum load on the ramp is the number of people that are likely to be there at the same time. 5,6? And of course there will be 2 beams one at each side. Yes, I can over engineer it but the limitation is that I have to be able to lift the bloody thing without a crane, so I was hoping to use the smallest possible size and bolt the handrail to it after it is in place. 
Perhaps the steel supplier can help.

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## woodbe

Why not use aluminium?

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## Marc

I am hopeless at welding aluminium.

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## ringtail

What about making a web truss out of much smaller section ? 50x50x5 maybe. A bucket load of welding though

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## Moondog55

Wouldn't the handrail do exactly what you want?
Vertical strut in the centre and 2 diagonals at 45 either side Vertical at each end and a 45 to the base then the handrail becomes the load carrying member and the bottom rails are just for live load support, a bridge in other words
Mind you that is only the picture in my head as I am not an engineer
How are you going to get the rust protection you need?

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## dmac

Why not lay the two lengths side by side with a block of wood at each end (on the ground rather than over the water..).
Get a bunch of your mates to jump up and down on it and see how it goes. 
Dave.

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## Marc

Yes, well, that is the plan. A pony truss or web truss on each side would help the main beam and allow it to be much smaller and lighter. 
If I could find a table like we have for timber, I could work out easy the minimum size for this job. I think I have to give this to an engineer to work it out properly. 
Yes, the test of the mates jumping on it would work if I had the RHS beam already. i hope to work out the right size before I buy them. No good buy 150x50x5 if I need 4mm or 6 mm or may be only 100x50x4 
As far as the process to build it, I'll make the main beam first with the two anchoring points at each end and attachment points for diagonals and handrail/truss. 
The handrail built separately to be bolted on. All goes for hot dip galvo. Once back, I can attach each beam one at the time to the shore and the pontoon. Then bolt the handrail on and last screw the floor boards one by one.

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## ringtail

This may sound silly but have you looked second hand ? I know after the floods up here there were hundreds of complete pontoons and walkways piled up for collection / sale. Most people just claimed new ones on insurance or were too scared to claim them back as there was a rumor that council were going to fine people. The fines never happened and nearly all the pontoons and ramps were scrapped. Most were in decent condtion.

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## Marc

Well, not so silly. I got the pontoon second hand 2 years old for 1/5 of the price new. I have not seen ramps but it may be worth searching for one. The ramp new is worth a bomb, the manufacturer is in our area so that was my first port of call. 
I'll give it a go.

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## Marc

A search on gumtree found one pontoon and ramp but too long for me (7 meters ramp). Nothing on ebay nor google.
May be you can find me a ramp that is 4.5 to 5.5m long in a scrapyard? 
If you have the time that is. I'll pay you finders fee  :2thumbsup:

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## Marc

Found the plans for aluminium ramp 4m long and 6m long
4m http://www.bmackay.com.au/mds/drawings/a4-1575.pdf
6m http://www.bmackay.com.au/mds/drawin...00/a4-1940.pdf 
Notice that both use aluminium RHS 150x50x3 for the main bearers and a simple truss system very easy to reproduce in steel.
Both are wider than I need. I was thinking in 900mm wide being plenty.
 Now the question is if aluminium can be as thin as 3mm my presumed 150x50x5 is way too much which is good news. The marine construction websites that compare aluminium with steel construction say that an aluminium structure needs to be about 50% thicker to equate the steel equivalent.
Now that is for boat construction and I couldn't find any table comparing RHS allu and steel.  
What if I use the same size used in aluminium using steel? That in theory should be 33% stronger ... (?)

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## SilentButDeadly

I reckon you could get away with using the same section in steel... 
However, if you plan to get the whole thing hot gal dipped then you need to bear in mind that you can't have any sealed areas (due to risk of explosion) so every box section will have to be drilled and it will have to be a decent sized hole which might have structural implications for you. 
Honestly....I'd be looking to use pre galvanised steel C section purlins which can simply be bolted together... Stratco C and Z Purlins - Stratco C sections, Stratco Z sections, Stratco purlin, Stratco girt, light weight beams 
You might also consider keeping an eye out for some used aluminium boxed trusses...

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## SlowMick

Mark - you could use the tables in pdf above to figure out which PFC or UB you can use.  then jump on the bluescope website and find the section properties of your chosen section (http://www.onesteel.com/images/db_im...ledCat_web.pdf)
you can then compare the section properties to those to your chosen RHS.  
The RHS is a stronger steel that the UB/PFC (450 MPa vs 300 MPa) so if the RHS has a larger Ixx (second moment of area) in the orientaion you plan to use it in it will be an equivalent (better) beam.
Not really structural analysis  just comparison of one section to another.

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