Question

a) Explain differential movement and prevention in brick and concrete masonry. Where the control joints are must be located.

b) A 150 –ft exterior clay brick wall is designed for ½ -in expansion joints and a joint compressibility of 40 %. Determine the maximum joint spacing and the minimum number of joints required for entire wall. (Wall is going to be built in Lubbock TX. Temperature difference can be taken as 80ºF. Annual mean relative humidity is moderate 75>AMRH>50)

Answer 1

Differential movement in brick masonry & concrete masonry - It occurs due to the drying shrinkage, thermal movements, elastic shortening, and creep deformation causes by the different properties (cement property, aggregate property, stone property, mortar property) and mechanisms acting on the masonry.

Prevention of Differential movement in brick masonry & concrete masonry are in the following:

1. By introducing more reinforcing steel into the masonry to conter balance the shear stresses.

2. By providing support of vertically unreinforced masonry to limit the deflection of the members to the permissible levels.

3. By introducing proper movement joint into the masonry to regulate the deflection of the masonry structural elements.

Control Joints - Control joints are provideed as the vertical seprators and must be located into each wall to resist & to reduce the longitudinal movement of the masonry.