Understanding beam calcs

[DIYStuart]

I've just had the calcs back from our SE for an RSJ to put in an opening. Nice document which very clearly says what I need to know ... "use a 152 x 89 x 16 UB and mount it in xyz pad stones", and what BC will need to know .... lots of numbers about load factors, buckling resistance, bending moments etc


Coming from a mathamatical, but not engineering, background I'm interested in what these numbers actually mean and how they are calculated. I've googled around and found bits and pieces about it but haven't found one nice clear article that describes it all in one place. Does such an article exist or am I'm looking at getting a book out of the library?

 

[wavetrain]

Stuart, coming from science background myself, like you, I wondered about these calcualtions so found this website http://www.structural-engineering.org.uk/

And download his 'steelbeam' spreadsheet and used it as a learning resourse. You will soon pick the BC lingo up.

 

[RonnyRaygun]

I've just had the calcs back from our SE for an RSJ to put in an opening. Nice document which very clearly says what I need to know ... "use a 152 x 89 x 16 UB and mount it in xyz pad stones", and what BC will need to know .... lots of numbers about load factors, buckling resistance, bending moments etc


Coming from a mathamatical, but not engineering, background I'm interested in what these numbers actually mean and how they are calculated. I've googled around and found bits and pieces about it but haven't found one nice clear article that describes it all in one place. Does such an article exist or am I'm looking at getting a book out of the library?

Have a read through this: https://steelconstruction.org/component/documents/?task=downloadDocument&doc=3545&file=3545
A good proportion of what you need to know can be found here (Chapter 3).

If you need even more detail you need to get your hands on a copy of BS 5950.

Load factors (usually 1.4 for dead loads and 1.6 for imposed loads) allow for errors in assumptions made in the calculations, manufacturing and construction errors, and occasions where house holders or whoever might accidentally (or deliberately) overload the structure.

Padstones simply spread the load at the end of the beam over a sufficient area so as to prevent crushing or cracking of the masonry below. For Victorian masonry we take 0.42 N/mm2. For modern brickwork you usually get a higher capacity than 0.42 but you need to do a calc based on guidance in BS5628.

You really don't want to do a buckling calc Or maybe you do, having a mathematical background
Basically it involves a complicated calculation (From BS5950) taking into account such things as buckling parameters, torsional constants, and the like. What it means is that an unrestrained beam will not develop its full bending capacity as the web will buckle due to compressive forces in the top flange.
Anyway, no-one ever works it out because they have all been done for you in the Blue Book.

 

[wavetrain]

I downloaded the book Ronny mentioned, however it is red not blue.

The spreadsheet programm I mentioned has built in the parameters of all the UB, UC RSJ & PFCs made. It is much nicer to use than printed tables.

 

[RonnyRaygun]

I downloaded the book Ronny mentioned, however it is red not blue.

The spreadsheet programm I mentioned has built in the parameters of all the UB, UC RSJ & PFCs made. It is much nicer to use than printed tables.

Aha! The Red Book and The Blue Book are two different books I don't know where The Blue book can be downloaded free...probably off some of those file sharing sites...but that would be illegal

As far as I can remember, there are no buckling tables for unrestrained beams in the Red Book.

I've also got the spreadsheet programme, but it doesn't really give you an understanding of what's going on without getting behind the numbers.

*Edit* You can download a copy of The Blue Book here . You need to register with Corus to get your hands on it.

 

[DIYStuart]

thanks to both of you .... some nice reading for me here

Stuff here I hadn't considered, but once you get down to the maths its fairly straight forward really.

 

[^woody^]

When I was studying beam design, I initially got confused with the formulae changing N, kN, kN/m, kN/mm2 etc in what seemed like a random way in different parts of the equations.

I asked a relative who had studied some sort of applied pure mathematics of some sort, and he was none the wiser either. lol

It's all clear as mud now though

 

[RonnyRaygun]

When I was studying beam design, I initially got confused with the formulae changing N, kN, kN/m, kN/mm2 etc in what seemed like a random way in different parts of the equations.

I asked a relative who had studied some sort of applied pure mathematics of some sort, and he was none the wiser either. lol

It's all clear as mud now though

Yup, forever multiplying and dividing by 10^6 and 10^3...

Just depends on what units you want to end up with...

 

[Static]

As already stated above i would go for, Steel Designers Manual and BS5950 as the two core documents for steel design..

 

[^woody^]

Hey, its all Eurocodes now ... non of that old fashioned BS 5950 stuff

Structural Elements Design Manual by Trevor Draycot is a good reference for those interested in a path to the dark side

 

[RonnyRaygun]

Hey, its all Eurocodes now ... non of that old fashioned BS 5950 stuff

Half the engineers I know are still using BS449!

Structural Elements Design Manual by Trevor Draycot is a good reference for those interested in a path to the dark side

Yeah, saw me through uni and still got it on my desk at work now...although if you are working to Eurocodes you want the new version updated by Peter Bullman.

And Design of Structural Elements by Chanakya Arya is very good also...

 

[Static]

Hmm, just downloaded Structural Elements Design Manual, will flick it over later..