Using steel columns to support beams

[mikeyb50]

I have been using superbeam & prosteel for a year now and it's being brilliant, I use it mainly for loft conversions and the odd thru wall openings. I recently came across an instance where instead of using the pad/steel for bearings I am required to use a steel column on either end of a 203 x 203 x46 spaning 5m to form an opening in a back addition victorian extension. Can superbeam provide this calculation and if so how. Is it similar to using timber posts to support ridge beam.

Any help would be appreciated

[Tony Bryer]

Yes, you can do this in SuperBeam and ProSteel - the procedure is identical. The usual way of doing this is to weld a cap plate to the top of the each column on which the beam then sits on, with a couple of small bolts for location. The load is assumed to act at the edge of the plate (i.e. applied at the face of the column) so creates a small moment in the column as well as the axial stress.

If your loading on the beam is symmetrical, you obviously only need to design one column. Otherwise repeat the procedure below twice, once for each end.

Once you have done the beam calculation and are happy with it, press the Add Column button. Enter a descriptive location and length; the effective lengths will probably be 1.0L.

On the first line of the load table enter 'A' in the load column and a suitable figure for the own weight of the column, say 0.1 or 0.2 - actual figure is rolling weight of selected section x length x 9.81 (kg>N)/100 (convert to kN), but you don't need to be too precise as its unlikely to affect the final calculation.

Then click on the second row, and then on the '1' button on the little diagram to denote where the load is being applied in relation to the column.

Then click on 'B/F' (bring forward reaction) and select your beam and R1. Press OK and the beam reaction will be added in as a load expression. Change the figure in the offset column to '0' as the load acts at the face of the member (the default 100 is for cleat and similar connections which are assumed at act at 100mm from the face of the member). Press 'Apply' and that's it. As with beams, you can go to the steel section page and choose an alternative section, and also tailor the baseplate to suit your situation.

Please come back if any of the above needs clarification.

[mikeyb50]

Thankyou that was very clear

[factory-fit]

I've found this ability a tremendous time saver when doing mezzanine floor drawings; by bringing forward the beam inputs for each column calculation, you can rapidly knock out the Live and Dead loads to annotate next to each location. This allows the Local Authority, landlords or other party to inspect the design to check it's effect on the concrete floor slab.

On a domestic or loft conversion this output of the loads will allow your advising civil Engineer to size up the base foundations, whether pad, pile or strip foundation.

It also helps when you already know the strength or load limit of the concrete slab; by playing around with the column locations it is possible to reduce the beam weight to the minimum, (by using cantilevered ends when they are buried in walls or behind features). At the same time you can flick over to check the column downloads are still OK. I now frequently cantilever any edge beams on mezzanines when the column can be hidden, as it isn't good to put loads right on the edge of a concrete floor. Another trick to often avoid the need for foundations at all, is to put a 'T' principal on the end of a beam going to a wall at 90°, and stand that on two columns, say 2-3m apart. this means more steel but is often less costly than the mess and delay of casting foundations.

Best rgrds

Kev

[Tony Bryer]

Thanks for the practical tips, Kevin

[chrisship]

I do hope that mikeyb50 is not a non qualified engineer carrying out structural engineering calculations, but the question asked seems to imply that; as any engineer would know how to use steel columns to support a beam!