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# Compression Strength of two different grades of brickwork

## Compression Strength of two different grades of brickwork

(OP)
Hi

If a beam rests on a wall consisting of two different strengths of brickwork, is it allowed to design the brickwork using the average strength.
Say the bearing length at 0.4 x the height of the wall under the pad-stone consists of 1.5m of brickwork of strength 1 N/mm2 and 1m of brickwork of strength 3.5 N/mm2 can I take an average to find a sort of "effective" brick work strength.

Thanks

### RE: Compression Strength of two different grades of brickwork

It is based on stiffness for the load transfer. Are you dealing with 4"CMU and 4"clay? or something else. i do not believe the strength numbers you are talking about really will be your failure, which is concerning.

### RE: Compression Strength of two different grades of brickwork

Probably should take the lower strength for bearing assuming the pad-stone straddles two different grades of brickwork.

BA

### RE: Compression Strength of two different grades of brickwork

I'd use the lower one for design, and if checking the absolute maximum load, use the higher one with the reasoning that it would be supporting the load as the weaker wythe 'crushed'.

Dik

Abuh001:

### RE: Compression Strength of two different grades of brickwork

Abuh -

How are you measuring the "strength of the masonry".

Most codes recognize the f'm, which is determined by testing of a prism consisting of masonry units and mortar. Masonry for code development is usually determined by testing wall sections (vertically loaded, shear and flexure) to account for the differences for the materials and the ability of the materials to work together. They have shown that the effect of mortar is minimal, which simplifies the structural analysis and supports the lack of requiring strength tests of on-site mortar.

Being a wall of different materials, it is best to design based a wall panel consisting of the materials being used. Obviously, site samples of a prism of masonry units and mortar is impractical and unreliable.

Take a look at the ACI 350 document since it has been adopted in many European and Asian countries.

Dick

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

### RE: Compression Strength of two different grades of brickwork

Concretemasonry:
I’m doing a slight thread highjack here...,

Dick, would you please look at the thread titled “CMU Disintegrating,” thread507-435859: CMU Disintegrating, 23FEB18, and tell us what you think on the subject. I would be interested to hear what you have to say, have you seen this before, what causes it, etc. All conc. blks. don’t seem to be affected the same way, all the time, even though in the same location, and while 5,6,7 blks. are severely deteriorated.

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