Rsj bearing help???

[Jbg123]

Recently had an rsj installed as dinning wall has been removed. Rsj sits on internal skin on a pass time, but only has 80mm bearing on each side? Will this be okay??

Thanks in advance

 

[KenGMac]

Jbg123, good evening.

on a pass time

Any chance of expanding on this please? is it a concrete pad?

What sort of span does the RSJ cover? and what are the RSJs dimensions?

Ken

 

[Jbg123]

Yes on a concrete padstone
Span is 2850mm
178x102x19 ub

Thanks

 

[Notch7]

Yes on a concrete padstone
Span is 2850mm
178x102x19 ub

Thanks

Your builder has used a 3.0m beam -I would've thought either 100mm or 150mm is usually the minimum (cant remember which)

 

[tony1851]

Although you would usually look for a 100 bearing, 80mm will be OK for the loading normally found in a domestic setting.

 

[oldbutnotdead]

Your BCO may want to see some calcs for an 80mm bearing, 150 is standard.

 

[noseall]

Your BCO may want to see some calcs for an 80mm bearing, 150 is standard.

100mm is standard for steel beams.

 

[tony1851]

The crushing strength of the average concrete padstone is around 50 N/mm²; when safety factors are taken into acount, this is reduced to around 20 N/mm².
If the beam is 102mm wide, and the bearing is 80mm, that gives a contact area of approximately 8,000 mm², so that the maximum load allowed on the padstone surface would be 20 x 8,000 N = approx 160 KN.
This is way, way above the load that will show in the SEs' calculations for the beam; it is not a problem.
There are other factors to be taken into account when using a short bearing, but in practice they would not apply in a domestic situation where the loads are relatively low.

 

[Notch7]

The crushing strength of the average concrete padstone is around 50 N/mm²; when safety factors are taken into acount, this is reduced to around 20 N/mm².
If the beam is 102mm wide, and the bearing is 80mm, that gives a contact area of approximately 8,000 mm², so that the maximum load allowed on the padstone surface would be 20 x 8,000 N = approx 160 KN.
This is way, way above the load that will show in the SEs' calculations for the beam; it is not a problem.
There are other factors to be taken into account when using a short bearing, but in practice they would not apply in a domestic situation where the loads are relatively low.

Its quite amazing really -it always looks so dodgy when you see a biggish steel with just 100mm bearing -I can see the logic in the maths though.

 

[^woody^]

I'll chip in with the ubiquitous "what do the design calculations say"?

Or are you printing out a thread from DIYnot and submitting it to the council for approval?