Stack bond cmu control joints

[twinnell]

Does anyone know if there is different criteria for contorl joint spacing for stack bond compared to running bond. NCMA recommends 25 feet max spacing but only shows running bond. I would assume it to be the same regardless, but another engineer that we are doing a peer review for says the max spacing is 50 feet. He can't provide any documentation to support.

 

[concretemasonry]

The same criteria applies for both running bond and stack bond walls. - A maximum of 25'.

Refer to NCMA TEK 10-2A; Table 1 and Table 2. This can be found on the NCMA site (ncma.org).

The main requirement is that you provide the minimum amount of horizontal reinforcement (usuaaly joint reiforcement or bond beam) of 0.025 sq. in./ft of wall height. This is based on the performance of many walls, using different aggregates under a wide range of conditions.

This method is based on the criteria for empirical design explained in that TEK Note. The empirical standard replaced the older methods that were unworkable and unrealistic since they did not fully address the different factors such as temperature expansion/contraction, carbonation shrinkage, wall restraint and drying shrinkage that that could be additive or subtractive depending on the conditions during construction and during service.

For very, very unusual conditions on how to conduct an engineered analysis. Frankly, even for the very unusual conditions the differences are minimal and the reliance on the collected material factors for the different materials is dubious.

Dick

 

[concretemasonry]

The last paragraph in my previous post referred to NCMA TEK Note 10-1A

Dick