# Homework Help: How to calculate yielding load for a concrete block?

1. Feb 23, 2010

### Pinj

Hi all,

I am trying to calculate by hand the maximum load that a concrete 1m x 1m x 1m block can take before failing. The load is applied uniformly across the top of the block.

I've found out that the average compressive strength of concrete is 70 MPa. Is there a formula that makes use of the compressive strength value to find the maximum load?

Thanks!

2. Feb 24, 2010

### Pinj

Finding the ultimate load of a concrete block

1. The problem statement, all variables and given/known data

My design project involves stacking up concrete cubes into a tower (think Giza Pyramids). Each cube measures 1 metre on each side and weighs 500kg. How many of such cubes can be stacked on top of one another before the one at the very bottom fails (ie. crushed).

Given that the compressive strength of concrete is 40 MPa or 40x10^6 N/m2.

2. Relevant equations

Pressure = Force / Area

3. The attempt at a solution

40x10^6 = Force / 1m2
Max. Force = 40x10^6 N

Number of cubes = Max. Force / force exerted by one cube
= (40x10^6) / (500 x 10)
= 8000 cubes

Somehow I think it ought to be more complicated than this because the depth or thickness of the material should also have an effect on the strength of the cube. Please advise, thank you!

3. Feb 24, 2010

### Studiot

Concrete cubes under uniform uniaxial compression fail in diagonal shear.

This is the standard method for testing concrete although the cube size is rather smaller than a one metre cube.

The method and relevant formulae can be found in BS 1881 part 116 : Methods for determination of compressive strength of concrete cubes.

Last edited: Feb 24, 2010
4. Feb 24, 2010