Typical movement joint spacing for unreinforced concrete masonry panels.
Movement joints in concrete retaining walls.
Movement joints such as control joints are one method used to relieve horizontal tensile stresses due to shrinkage of the concrete masonry units mortar and when used grout.
Greater distances between movement joints 9 m and sometimes longer are possible in aggregate concrete blockwork walls depending on the location and block type.
1 3 movement and restraint in concrete structures restrained movement is a major cause of cracking in con crete structures.
They are essentially vertical planes of weakness built into the wall to reduce restraint and permit longitudinal movement due to anticipated shrinkage and are located where stress concentrations may occur.
For cantilevered and gravity walls vertical expansion joint spacing shall be a maximum of 60 feet on centers.
In concrete walls the movement joints should normally be placed at a maximum spacing of 7 5m.
8 to 12m external.
Precast concrete cantilever wall expansion joints shall be in accordance with the standard specifications section 6 11 3 3.
The friction of the concrete is the key factor that limits the movement.
Expansion joints should normally be provided at a spacing of not more than 30m between successive expansion joints or between the end of the structure and the next expansion joint.
Tial basement walls and the national ready mixed concrete association ref.
As a rule of thumb it is normal to consider movement joints at approximately 6 m centres in straight lengths of autoclaved aerated concrete block walls.
4 recommends a contraction joint spacing of 30 times the wall thickness or 20 feet for an 8 inch thick wall 30 8 240 inches 20 feet.
6 to 9m factors influencing spacing of joints are.
Internal or external restraint can develop tensile stresses in a concrete member and the tensile strength or strain capacity can be exceeded.
The hight shear force is applied at the horizontal construction joints located at the lower level.
There is a special check to be done at the construction joints when larger retaining walls or structures having very high lateral loads are designed.
Contraction joints are usually about 0 25 inches wide and about 1 2 to 3 4 inch deep and are provided at intervals of not exceeding 30 feet.
Some designers recommend re ducing joint spacings by about 20 in walls with frequent openings such as doors and windows.
The weaker the mix the increased ability to accommodate movement.
