Bearing and Capacity of Existing Composite Hollow Clay and Solid/Tile Brick Wall

[NC_EIT]

I'm working on the renovation of an existing building with an extension to the mechanical PH. The record drawings showed a 12" masonry brick wall around the perimeter of the building. To extend the Mech PH, the new columns were to sit on top of the masonry wall. However, during construction contractor found that the wall is a composite of 8" hollow clay brick + 4" solid brick with top layer of loose tiles. The existing joists are also sitting on loose concrete grout. After this discovery, I'm not sure how to support my columns on top of this wall. Share if you worked on something similar and tell me how you would solve this issue.

See sketch below for ref.

Design Philosophy used: At the time of the design, the compressive strength of the existing units was unknown, we back-calculated fm' based on the maximum allowable bearing for solid brick wall and used calculated fm' to check wall capacity and sizing base plates under new columns.

Next question: as the wall is composite how would it effect the fm' of the wall to be used in the analysis?

Something similar to this wall is shown below.

Thanks.

 

[jerseyshore]

On terra cotta or similar crappy clay blocks I've always specified them to be filled solid. On those projects the loads were typically pretty small so I felt that filling them solid would create a nice grout column to support a beam. Anything of significant load I'd avoid and just have a new column installed.

Years ago I tried to do research on terra cotta because a client wanted to expose a portion of existing foundation and thus turn it into a small retaining wall. There are some historical resources out there that give a little idea about strength of these old blocks. Unfortunately I don't have them handy anymore.