Existing masonry shear wall

[yarsky]

I am to evaluate structural capacity of existing masonry building. (5 sty., unreinforced brick walls, about 100 years old). Of course, no records exist.
Any ideas of how to determine actual F'm? I guess there should be some lab test. What test? How to order one?
I would appresuate your input. Thank you.

 

[dik]

You can cut a coupon from the centre of the wall and test it if you have sufficient testing equipment. If the wall is of historic importance, you may not want to damage it and just try to get some historic strength information from early texts on masonry construction.

You can quickly do an analysis of the wall and determine the stresses from bearing and shear and see if the wall should be capable of supporting these types of loads. If compressive stress is 10 psi... you mignt not be concerned if the wall is stressed to that level... if the stress is 100 psi... you might be concerned.

FEMA has information on checking existing structures.

If memory serves, there was an organization call the Clay Masonry Institute (about 1950) and their publication/text that may have reasonable allowable stresses...

Historic Brick is a fascinating and rich area of study. I don't like to see the brick walls damaged.

Dik

 

[WBUW]

If you need to figure out f'm on a brick structure, and its high enough where you are worried in plane shear testing can be done.

Basically you remove one brick as gently as is possible with a roto-hammer, then use the roto-hammer as a drill and drill out the mortar at the vertial joint in plane with the removed brick. The head joint? Don't remember, its been a few years since I took masonry. A hydraulic ram with bearing plates on each side is inserted where the removed brick was located. The ram needs be be calibrated obviously, the load is slowly increased until the mortar cracks. The load is recorded and the test is repeated however often it is specfied.

This gives you the shear capacity of the mortar after you do some math (remember there is more than one side that was in contact), its been a long time but as I recall there is a formula relating the in plane shear strength and the compressive strength. ACI or something, I don't recall.

Anyway, thats how its done if you really need it. You will probably have to contract out to a testing firm to get it done.

G'luck

 

[RareBugTX]

Can you provide information on the purpose of the investigation. Are you adding new floors, changing occupancy, altering the structure?. Checking shear, bearing, out of plane,in-plane, pull-out,foundation????? NSI

On the other side, I would try to be more practical, and as one of the fellows above mentioned, I would look up some very conservative values and perform the analysis and investigation accordigly.

I have run into this problem before and the unreinforced concrete foundation proved to be the controling factor (we where adding a rather heavy, residential floor above)