how would you calculate windloading with signage?

[Martin Pearson]

Nick, try doing a search on the boards because it has been talked about before and there is defiantly software you can buy and I think it was mentioned in one thread.
I use to get a quote from Ashby because I knew they would use the right components, then sometimes I would use them and sometimes I wouldn’t. May not be quite the right way to do it but I did use to buy from them some of the time.

[Stephen Morriss]

I sometimes do the same as Martin but I do buy most of my sign blanks from them so they’d be getting the job anyway.

Calculating this sort of thing is very complicated as you need to know how much to put underground and how much concrete to use etc, also wind speed increases as you get higher off the ground.

Steve

[Steve Morgan]

As Martin says, there was a long thread about this some time ago. A good friend of mine is a civil engineer and he explained that there is a general figure that they use for calculations and if my memory serves me correctly it is 15lbs/ft²,I’ll ask him again on Monday.
You then have to calculate the bending force that the panel will exert on each pole at ground level. Force x distance.
It becomes a very complex subject the higher you go and also in coastal situations and I remember that this figure was for general urban areas.

Remember that the point where the poles go into the concrete will be the where the pole will probably fail, so an angled support joined to the upright, the higher the better, will give extra stability.
Have a look at some large road signs, they’ll give you an idea of what to expect.
If in doubt get some professional advice.

Steve

[Graeme Harrold]

Have a quick look here

http://www.ha-research.gov.uk/projects/index.php?id=966

There is a lot of technical information and a couple of worked examples at the end. Unless you are placing the sign, its calculations you want to stay clear of unless you have a good mathematical background. Working out the size of foundation required, but ensuring the materials can withstand the wind loading is another.

Points to remember:

• Loading forces increase exponentially as the wind speed increases
  Bending moment forces increase as the pole length increases
  Wind accelerates round buildings……..

And the list is practically endless

If you have any questions about the maths PM me……… 😮

[Andy Gorman]

I have reservations about the correct size of fittings for use on projecting signs. Weight is an easy one, but allowing for wind resistance is another.

What do people use for projecting lightboxes, for example?

[Martin Pearson]

Andy, I’m not sure if wind loading would be a major factor with projecting lightboxes. Think the weight is probably more of an issue.
If you got really high winds I would think that the panels would blow out before the box could be ripped off the wall.

[Andy Gorman]

Hmm, maybe. It’s one of those things that would keep me awake at night though.

For example, I’ve got a 3′ x 2′ x 160mm box to fit on Sunday. I intend using those expansion bolt things, what length and width of bolt?

Anybody?

[Martin Pearson]

Andy, does the mounting bracket have holes in it and how many are there?

[Andy Gorman]

Yes, it has one of those box type mounting brackets with a lip down the sides, 6 holes.

It’s a re-position job. It had I reckon M10s in it before, but I don’t know what length as they are a bugger to remove.

[Martin Pearson]

What is it getting fixed to? Is it a brick wall and is it rendered?

[Andy Gorman]

Nice solid brick. I know that because our whole town centre is built from very solid Victorian era brick.

[Martin Pearson]

In that case Andy I would probably go with about an M14 size anchor bolt about six inches in length. Will mean you need to drill holes about 19 or 20mm diameter, can’t remember the exact size off the top of my head.
I would also use something like large penny washers as well to help spread the load.

[Andy Gorman]

Thanks Martin. It’s a good idea to go overboard on something like this I reckon. The fixing hole size isn’t a problem, I bought a brilliant Dewalt SDS a few months ago and it makes mincemeat of even the hardest brick.

[Martin Pearson]

Andy, I don’t think it is going overboard. To me it’s just making sure it is safe and it’s not like there is a huge difference in the price of the fixings.
With 6 fixings using something smaller will only save a few pence anyway.

[Robert Lambie]

Ive always used the large brass rawl type fixings for projecting signs and the like. but i hate using them. they can break up or get jammed easily, when this happens your beat! great fixings but tempromental unless you have the knack to using them.
in the past 18 months i began using Concrete screw/bolts (sorry dont know technical name for them) 😀
you drill a 7mm hole into the concrete, then using a socket set, just crank in the screw. it goes in easy and cuts its own threads into the concrete as it goes. they come in various sizes/lengths but i normally the 6-8 inch long ones. if you are going into a nice hard brick, these things are really solid. the box frame will break well before these come loose.

the only time i am dubious about using them would be in a soft sand stone or the like. also, be sure to dril a nice tight hole. dont widen it any with the drill bouncing about etc.

[Martin Pearson]

Robert, we are talking about the same thing, I call them anchor bolts but don’t really know what the proper name should be. I have never had any problems with them though, as long as the hole is drilled at the correct diameter and cleaned out before inserting the expanding section they have always been OK with me.
Never been to sure about self drilling type fixings especially with heavy loads are concerned so have never looked at the other fixings you use but will look out for them.

[Nick Dowell]

Thank you for your help everyone. I have asked Ashby for a quote to gauge the size posts etc… to use and we will see how we get on.

This actually brings me on to my next question…

We also have an enquiry for some projecting light boxes/flex face boxes… though they are to be 1500mm x 1500mm. Obviously this is quite a size for a projecting sign so I would guess would need some form of wire support system?

…. Or just say it cant be done (which I don’t really like doing – id rather some back with a solution)

Nick