Masonry wall and possible earthquake retrofit

[woodman1967]

Hi all

We're working on reno-ing an old building to convert it into a trade school.

There are two 8" unreinforced masonry walls 70' long and 20' high. These walls are not structural.

The concern is earthquake design. Though the walls are not part of the seismic forces resistance system. Would this collapse in an earthquake is their concern. We are located in eastern Canada. One wall has no openings the other has a man door in the middle and two small windows on the second floor (again, no connections to the structure of the second floor etc).

Should earthquake be a concern?

Thanks for your help.

 

[SlideRuleEra]

IMHO, the short answer is "yes", but a lot depends on the details. In the most general terms an earthquake below 5.0 on the Richter scale is usually considered "minor". Since your question is very broad I suggest taking a look at the historic Modified Mercalli Intensity Scale to get an idea of the level of damage that can be expected for various intensities. A correlation with Richter is provided:

http://en.wikipedia.org/wiki/Mercalli_intensity_scale

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[concretemasonry]

How old is the building? I assume the question came up because of a change of use and not any modifications.

Do you actually know what the construction of the existing wall is. Frequently, a wall may be described as "unreinforced" but there may be minimal non-structural steel (4' O.C. or something similar), but steel was used for continuity and was not structural reinforcement since the wall is non-bearing.

That is a pretty high h/t for the wall. Is it interior or exterior?

What is the 8" wall constructed of? - Concrete masonry or multi-wythe clay brick construction? Is there any horizontal joint reinforcement.

Answering the question of "Will it collapse in and earthquake?" is a pretty open question and could take some investigation to give an answer the you are will to sign on the line for.

Dick



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

 

[woodman1967]

Thanks for your responses.

The wall 8" concrete masonry walls and it is known that it is not reinforced whatsoever. There are two walls (one interior and one exterior). I am not sure of the age of the building but it is a change of use (from industrial building to trade school).

Thanks again.

 

[hokie66]

The unreinforced external wall would not work to resist wind loading, regardless of the earthquake requirement. For a trade school, I think these walls should be built to current requirements.