Bearing of Blockwork

[LivingTheBeam]

Hi All,

I was wondering if there is any guidance or general rules of thumb for say the bearing length of blockwork on a steel support.

I have a situation where the architect wants 140mm wide block to bear onto a UB by only 100mm (40mm projecting off in order to fireboard and have a flush inner face).

I was trying to find anywhere in the codes if there was any requirements for minimum bearing? I know a check could be done to see if the shear capacity of the reduced contact area is sufficient to resist the lateral forces but my own gut feeling is that I would want full bearing (this wall is to act as a barrier in an escape stair enclosure).

Any insight is much appreciated.

 

[concretemasonry]

Aidan -

More information is needed.

In your area, what does "UB" refer to?

What codes are you referring to?

Is the 6" wall load bearing or just a non-bearing facade.

What is the shape of the block for the first course of the 140 mm wall wythe? I am sure there is some minimal vertical steel in the wall even if it is not loadbearing.

Treating the joint in the wall as being a corbeled wall is allowed in virtually all codes to an extent. Keep in mind that the the loads withing a concrete masonry wall are distributed at about a 45 degree angle. This is verified by the failure patterns in the typical 2 block high to determine the masonry (f'm). A reference could be the ACI 530 document that describes the code and specifications of masonry for the U.S. and many other countries. I have seen this detail on many 6" high rise load bearing structures(up to 10) stories).

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[tony1851]

(@ Dick; "UB" = Universal Beam, a UK designation - similar to wide-flange "I" beam; and if OP refers to a block wall, it is unlikely to be reinforced).

@ OP; if you are overhanging 40mm, you might be inducing torsion and other problems in the beam (is it a 203 x 102?)
Maybe you should speak with your architect rather than bust your gut trying to accomodate a poor concept of his.