double wythe cmu retaining wall

[Igotquestions]

I have a two wythe load bearing CMU wall composed of 6” and 8” block. The 6” cmu will carry the brick above grade. The 14” wall is 14’ below grade and is fully grouted (both wythes). I need to find out is if both wythes can act together and can I assume the wall is 14” thick. Can this be accomplished with joint reinforcement? If I can get a little advice I would appreciate it.

 

[dutchie]

it is my understanding that the double wythe wall can be considered as one 14" unit provided it is properly tied with unit ties and standard joint reinforcment. one publication i have read states that the unit ties should be provided for each 2.75 square feet of wall, or a spacing of 16" horizontally and 24" vertically, with standard joint reinforcment at every 16" vertically.

good luck

 

[JAE]

If the unit ties are wires, and there is no grout between wythes, then each wythe will act independantly in bending. For the two wythes to act together, you must tie them toegher to resist the shear forces between them - this can only be done with grout or some rigid-type tie. I don't know if your unit ties are intended to take the shear or not but wire ties will not do the work required.