Movement Joints In Concrete Retaining 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.

Movement joints in concrete retaining walls.

Tial basement walls and the national ready mixed concrete association ref. Greater distances between movement joints 9 m and sometimes longer are possible in aggregate concrete blockwork walls depending on the location and block type. 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. 1 3 movement and restraint in concrete structures restrained movement is a major cause of cracking in con crete structures.

The friction of the concrete is the key factor that limits the movement. The hight shear force is applied at the horizontal construction joints located at the lower level. 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. Some designers recommend re ducing joint spacings by about 20 in walls with frequent openings such as doors and windows.

Typical movement joint spacing for unreinforced concrete masonry panels. 8 to 12m external. Use of bedjoint reinforcement and moisture content of blocks when laid. The weaker the mix the increased ability to accommodate movement.

These are vertical joints or grooves formed or cut into the wall that allows the concrete to shrink without noticeable harm. 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. Internal or external restraint can develop tensile stresses in a concrete member and the tensile strength or strain capacity can be exceeded. Precast concrete cantilever wall expansion joints shall be in accordance with the standard specifications section 6 11 3 3.

6 to 9m factors influencing spacing of joints are. For cantilevered and gravity walls vertical expansion joint spacing shall be a maximum of 60 feet on centers. 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. 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.