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OT - Any strutural engineers on here today ?
mcerd1 - 7/10/09 at 06:07 PM

I've got a bit of a problem with a structure I'm designing at work, basicaly I need to reduce the wind load on it....

Its only a tempery structure, but its going to up throught the winter so I can't save anything on the seasonality factors

I'm using BS6399-2 for the wind loads and thinking about using a lower probability factor (instead of the standard 50 year wind)

anyone got any experience in playing with these factors ?

any other suggestions ?

cheers
-Robert

Howlor - 7/10/09 at 07:10 PM

It'l be reet!

mcerd1 - 7/10/09 at 07:26 PM

quote:
Originally posted by Howlor
It'l be reet!


not at 900 tonnes of concrete for a tempary structure it won't

rachaeljf - 7/10/09 at 07:38 PM

Read Annex D of 6399-2. It shows you how to derive different values of Sp for different return periods. If your structure will be up for only a year for instance, you can use Sp = 0.749 (see Note 1). Using this, your qs will be reduced by 0.749^2, i.e. about 50%, quite a handy reduction!
Cheers R

Guinness - 7/10/09 at 08:37 PM

What will it squash if it comes down?

A school? or some cows?

I'd be doing some risk analysis before taking out any strength from it.

Mike

mcerd1 - 8/10/09 at 08:04 AM

quote:
Originally posted by Guinness
What will it squash if it comes down?

A school? or some cows?

I'd be doing some risk analysis before taking out any strength from it.

Mike


Its a crane in our own yard for errecting another structure

the problem is that I've no experience of risk assesment
thats why the initial design was for 50 year wind (Q= 0.02, Sp= 1.0)

so where do I find guidance on acceptable risks ?

rachaeljf - 8/10/09 at 08:49 PM

Who is supplying the crane? They should do all that for you. Crane design is not quite the same as a normal structure, there are dynamic effects to take into account.

mcerd1 - 11/10/09 at 01:14 PM

they arn't interested

rachaeljf - 17/10/09 at 09:47 PM

It sounds like you are buying/hiring a pillar crane or the like, and you have to design your own support structure for it, using some 375 cubic metres of concrete? I suggest you engage a structural engineer.

Cheers R

mcerd1 - 18/10/09 at 05:53 PM

its a beam crane

rachaeljf - 18/10/09 at 08:34 PM

Well, give us some info on the crane and we might be able to help!

Peteff - 19/10/09 at 09:45 AM

You can hire mobile cranes to lift up to 1300 tons nowadays. How much is the 900 ton block of concrete going to cost to get installed and removed if it's temporary ?