## Bracing structures - stability

## Bracing structures - stability

(OP)

How do you go about calculating the horizontal deflection in a braced structure by hand? Sorry if this seems a really dense question - I've never had to calculate it by hand before but I can't get a FEM model to work properly and I'm confused.

I have attached a picture of the problem -> http://imageshack.us/photo/my-images/718/horizforcebracedstructu.png/ The blue dots indicate moment releases - suppose the frame is stabilised 'into the page' by already given means. If anyone can work it out using guidelines in BS5950 then that'd be even better, though I know a lot of you chaps are American.

The British Codes give lots of advice as to what limits to work to but when actually calculating the deflection using elastic analysis there's no help and I can't find any reference material which will help me either! Grr.

Regards,

A very stupid feeling NJonesUK.

I have attached a picture of the problem -> http://im

The British Codes give lots of advice as to what limits to work to but when actually calculating the deflection using elastic analysis there's no help and I can't find any reference material which will help me either! Grr.

Regards,

A very stupid feeling NJonesUK.

## RE: Bracing structures - stability

In any event, this is what I used when trying to calculate deflection of a braced frame by hand. I think I stole this from a previous post on this forum.

## RE: Bracing structures - stability

But yeah, that is exactly the kind of info that I'm looking for. Where did it come from?!! Why isn't it printed in every structural steel document ever?!!

## RE: Bracing structures - stability

## RE: Bracing structures - stability

I don't think that brace is going to work. That is probably why you are having problems with the computer model. I think you will need a column on the far left side to get the system to work, otherwise you need to make a frame out of it (fix the connections).

## RE: Bracing structures - stability

## RE: Bracing structures - stability

## RE: Bracing structures - stability

## RE: Bracing structures - stability

Michael.

Timing has a lot to do with the outcome of a rain dance.

## RE: Bracing structures - stability

## RE: Bracing structures - stability

I grabbed a copy of the braced frame deflection calcs SteelPE had uploaded. I was going to put it in my work folder for future use as it would be handy.

Just to be sure all was okay, I tried to prove the K-brace formula. However, I am getting a factor of 4 difference in the last term.

I uploaded the proof and if anyone has a minute, can you see an error in my proof?

thanks all

## RE: Bracing structures - stability

If you apply P=1/2 to each end of member 3 and break member 3 into two members with length L/2. The force (n) in each member is 1/2, (n) squared is 1/4, multiplied by L/2 = L/8, sum both members = L/4, which corresponds to the second part of the equation. I'm not sure if that is the correct way to do it, but it matches the equation.

## RE: Bracing structures - stability

Yup, that looks correct and works out well. Funny thing, when you think about it, if P is applied to on side only, then all of P end up in the braces and nothing on the last half of the beam.

thanks again

## RE: Bracing structures - stability

## RE: Bracing structures - stability