Span Length

[catmando2222]

When entering the span length in a beam calc program like Superbeam should it be the clear span or the span between bearing centres?

I have two load bearing walls 6m apart which I wish to span for a loft conversion. The beam will be placed on 100 mm wide bearing plates or pad stones so the distance between bearing centres will be 6.1m. Should I use 6m or 6.1m for my bean calculations?

Thanks

 

[^woody^]

Oh dear, you have got the program and just want to put some figures in to get it to throw out a beam section size?

Don't you need to work out the effective length as per BS5950 or does superbeam still use the earlier superceded BS449?

 

[freddiemercurystwin]

 

[catmando2222]

Oh dear, you have got the program and just want to put some figures in to get it to throw out a beam section size?

Don't you need to work out the effective length as per BS5950 or does superbeam still use the earlier superceded BS449?

I am using Superbeam 4 which is based on BS449, a copy of which I don't have. I thought it was a straight forward question - 6m or 6.1m? Or any I completely confused!

 

[Alarm]

Ask a Structural Engineer or an Architect.

 

[^woody^]

Ask .... an Architect.

LOL. An Architect can colour a beam in pastel colours, but not design one

 

[^woody^]

I am using Superbeam 4 which is based on BS449, a copy of which I don't have. I thought it was a straight forward question - 6m or 6.1m? Or any I completely confused!

I'm not sure about BS449, but in BS5950 you multiply the clear span by a factor based on the bearing restraint conditions - not just use the distance between the bearings or centre of the bearings.

Perhaps an older SE (Static? )on here may help with the older standard

 

[Alarm]

Ask .... an Architect.

LOL. An Architect can colour a beam in pastel colours, but not design one

But he can design the room and a SE can do the calcs

 

[RonnyRaygun]

I don't often use BS449, but looking at the standard now...

Clause 26 determines the effective length of the beam, based on end restraints, where the worst case is "L = 1.0"
But, where the load is applied to the top flange the effective length shall be increased by 20%.

And, from clause 19, Tables 3 and 4 apply to ordinary building structures
with simple end connections such as end plates or cleats. Where the end connections provide less restraint, the effective length l obtained from Clause 26 shall be increased by 10 per cent.

The above will refer to such instances as a beam sitting unrestrained on piers, and personally I would do the same in a knock through where there is also little lateral restraint.

So similar to, but more simple than, BS 5950.

So to answer the original question, I personally always go to the centre of the bearings for the overall length, but you will also need to know what effective length to take based on your restraint conditions.

Get everything else right (steel grade, loadings, etc) and Supabeam should spit out the correct answer.

 

[Static]

Pfft.. better to take Le as 1.2L + 2D where L is the clear span..
Course never used superbeam so dont know what its asking for or if you can modify the factors..

 

[RonnyRaygun]

Pfft.. better to take Le as 1.2L + 2D where L is the clear span..

Yeah, would do that if using 5950.

Course never used superbeam so dont know what its asking for or if you can modify the factors..

Got the demo version and you can set the effective length to anything you like