Faraz Korimbocus

Try to use Prokon to design brick/concrete masonry.. Its design is straightforward .. from load distribution of slab, corresponding slab load transferring into the supporting walls are calculated, the load keeps on adding down from each floor together with the wall line loads down the wall footings. Fk for characteristic compressive strength for the wall is calculated from the ultimate loads, the fk of the bricks or concrete blocks used taken from the manufacturer is checked then with the calculated one, if the brick/concrete blocks are adequate to bear the ultimate loads. Try to consult ACI 530-1999 or BS 5628-1985 for this type of design.

This one is mostly a practical issue.. If ever cube strength fails after 28 days, say for example the concrete compressive strength with which the structure was designed was 30MPa, and from cube test or non-destructive testing, the compressive strength has been found to be half, 15MPa only. Most consultants usually instruct demolition of the concrete element and re-casting. From a calculation which i made manually, I found that fcu(symbol as per BS 8110) has very little effect on reinforcement calculation. Even if fcu is halved when calculating again, new steel reinforcement calculated may increase by only 2-3%. Furthermore, fcu affects the value of Modulus of elasticity E, which in turn affects stiffness of the member producing a change in deflection of beams for example. But the effect is not so much prominent though, it may still pass in deflection also. Can anyone ellaborate more on this issue, if ever cube strength fails on site, final instruction will be based on what for an engineer supervising on site.