Masonry Head Joint

[walteraz]

I am not sure where to begin on this topic regarding the design of masonry. The architectural plans are showing a 1/4" x 8" x 8" glass inserts at random head joints. Not all are to be filled this way, maybe only 1/4 to 1/3 of the joints. What does this do to the strength of masonry and how does one begin to analyze this?

The closest code material I have found on this topic is the Specification for Masonry Structures (ACI 530.1/ASCE6/TMS 602). Part 3, Masonry Erection, simply states bed and head joints shall be 3/8-in.

Thank you for any input or experience you may share on this subject.

 

[dik]

Have to watch out... some alkali in mortars can etch glass...

Dik

 

[concretemasonry]

Are the glass blocks a structural element or does the specification apply to the proper installation of a traditionally used product?

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[walteraz]

To clarify, the wall is concrete masonry, with mortar joints. It is a structural wall, the exterior wall of a small office building. The inserts described above/previously at random head joints is the only glass involved.

 

[concretemasonry]

walteraz -

If they are minor architectural inserts, they should be neglected and the wall will not fit into the "cookie cutter" specifications.

Unless the real wall loads do not cause high stresses in the masonry units, the non-bearing, unbonded pieces of glass can be considered as voids structurally. If there are a substantial number placed closely, it could be a structural problem.

Glass block are generally no considered loadbearing because of the difference in properties compared to other masonry units and different mortar is required. A glass block panel is normally considered as a hole in the wall with a proper lintel.

Since a masonry wall is really designed as a structural element, there is no real criteria for anomalies that depend on percentage, spacing and location. Because of the common simplifying assumptions and factors of safety in CM masonry design, there may be no structural problem, but architects often have artistic license, so a structural engineer must at least point out the problem and go on record and pray for reasonable resolutions.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.