Help understanding my structural calculations

[TheWik]

Hi everyone.
I'm after some clarification around my structural calculations.

As you can see from the attached in having a near 5m beam installed one side of my new extension.

The beam will rest on a single leaf of 100mm thermalite blocks with a 440mmx215mmx100mm padstone in place one side and the inner leaf of the cavity the other. Again 100mm thermalite with the same sized padstone.

I don't understand at all how I can use a 100mm padstone when the structural calculations call for a minimum 150mm end bearing for the beam.

My structural engineers has suggested a 600mm x 100mm x 20mm steel spreader plate could be used instead but again I don't understand as the end bearing requirement is 150mm.

Does 50mm of the beam just overhang the padstone. 50mm into the cavity wall? Touching the insualtion?

This just doesn't sound right.....?


Thank you

 

[stevie888]

It's fine.

We like to have 150 min when the beam is in the line of the wall and the padstone is parallel to it. This helps to spread the load over the while length of the padstone.

When you go into a wall at rightangles things are actually easier as the padstone is now symettrically loaded.

Your SE isn't helping by giving you a calc showing a 250 x 150 padstone. What matters is area so if he wants 150x250 then 100x375 gives the same area and thus the same bearing stress and crucially fits the wall it's landed on. Wheer on earth the 100x600 steel plate comes from is anyone's guess.

%m is a fairly long beam in the scheme of things but it's not carrying a great deal of load.

 

[TheWik]

The steel spreader plate has been rejected outright by building control. So that's fine.

So to confirm the padstone of 440x215x100 will be installed as would a normal thermalite block in the inner leaf wall and the beam will sit centrally on the 100mm width of the padstone hanging 50mm into the 150mm cavity?

This is correct?

 

[stevie888]

You don't need the 50 overhang