Steel beam selection

[RonnyRaygun]

When I was 18 I did a summer job labouring at a water treatment works which was under construction.

We spent weeks filling the huge RC water filters with graded material.
Pebbles on the bottom, then gravel, then sand, topped off with anthracite.

Up two flights of stairs with 50kg bags on our shoulders before dumping them into the pit...every day! Only got a break when it came to rake the material level...never been so fit!

 

[russellsmiler]

Most of my beams are knockouts in the cavity wall, therefore will be having 2 no steels side by side on each masonry leaf.
Was planning to have web drilled along its length at say 600mm C/C 12mm diameter, and instal metal tube sleeve between the beams (loose) threaded bar(10mm) through this with washers and bolts tightened.

Question, what category of design do i use
1. Restrained
2.Partialy restrained
3. Unrestrained.

Russell

 

[tony1851]

Almost certainly somewhere between 1 and 2, or possibly between 2 and 3 - maybe, or perhaps not, but then again..........

Along with "effective length", this is one of those instances where a bit of engineering judgment is needed.

 

[noseall]

Does a beam need to be mechanically fixed to be restrained?

 

[tony1851]

Does a beam need to be mechanically fixed to be restrained?

Theoretically, yes, but in practice in many cases, no.

 

[RonnyRaygun]

Does a beam need to be mechanically fixed to be restrained?

Theoretically, yes, but in practice in many cases, no.

Documents I've read say that a heavy concrete floor bearing onto the top flange will provide full restraint, but to get full restraint from a timber floor you need to have the joists coming into the web, or decent mechanical fixings.
Some engineers I've worked with always treat beams in timber floors as unrestrained...might be the same people designing your beams Noseall

 

[^woody^]

"Restraint" normally refers to restraining the top [compression] flange to prevent lateral torsional buckling along the beam. The restraint comes from friction

A continuous load on the top of the beam (from the wall) will mean full restraint, but point loads from spaced joists may not due to the spacings

Joists fixed in to the web, and noggins can offer restraint from buckling, but not in the same way as loading of the flange, so as Ronny says it may be best to treat this loading scenario as unrestrained or partial

 

[RonnyRaygun]

Russell, here's the document I was talking about. You'll need to enter your email address to view the document.

Pretty heavy going, but the following examples should give you all the information and guidance you need for your designs.

Case 2 on page 20
Case 6 on page 27
Case 7.1 on page 28
Case 11 on page 35

Do you have a copy of the Blue Book? I can email a copy across to you if you need it.

 

[russellsmiler]

Ronny
Thanks for your help, Its many years ago since i was doing this sort of stuff, and even then it was quite basic!!.
Enjoying this though, hopefully when i get started i can keep this thread alive and go through my design process, calculating loads, designing padstones, designing beams etc.

Thanks again

Russell