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RE: hollow red clay block

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Although it has been a long time since I’ve addressed this one – possibly Nels Roselund is most familiar with the answer to this one. As I recall, there were two kinds of hollow clay tiles – one was structural with a wall thickness of around ¼” or thicker and the other was a non-structural clay somewhat less than ¼”. The non-structural clay tended to shatter in seismic activity and the structural clay tiles performed okay in the Venice and Arcadia areas that I encountered them. The greatest problem was the H/t ratio as most of these walls were one wythe and generally only 4-inches to 6-inches thick. I had a one story apartment building in Venice that I retrofit in the late 80’s and it performed decent. However, it had a raised floor and a flat roof. I used the partitions between units to brace the walls and tied the floor, ceiling and roof diaphragms to the tile walls. Were counters were set adjacent to the walls (such as in a kitchen), we even used these to help brace the walls. Most of the built-in’s were stronger than the tiles and we used these to help reduce the height to width ratio of the unbraced walls.

The building held up pretty well after the Northridge Earthquake with very little damage. It was a “U” shaped building and the wall subject to the most stress using the old RGA 1-91 for the city of Los Angeles was the inside short wall of the base of the “U”. This wall extended to the full width of the building since it also acted as a separation between apartment units.

We did anchor testing on the building and surprisingly, it held up well.

The only thing I recall that was tricky was making the determination as to whether or not we were working with a structural clay tile rather than the more brittle thin wall tiles. I saw more of the non-structural tiles in Arcadia and Huntington Park area of Los Angeles County.

Nels may have more information to offer on this, but unless the code changed since then (I haven’t done a URM retrofit for over 10 years) then I would think what controls the acceptability of the design is the testing of the walls for in-plane shear.

You might also check with Tim McCormick of Specialized Testing who may be one of the last of the testing agencies with a long background in Adobe, Clay Tile and Red Brick.

 

Dennis

 


From: Robert Freeman [mailto:robert.freeman(--nospam--at)idsse.com]
Sent: Thursday, January 18, 2007 10:26 AM
To: seaint(--nospam--at)seaint.org
Subject: hollow red clay block

 

Hi Jim:

 

We call it hollow clay tile.  Here in earthquake country it is a hazard.  We have recommended removing or strengthening these walls.  It is not allowed by code in new construction.

 

Respectfully,

Integrated Design Services, Inc.

 

Bob Freeman, Architect

Structural Designer

(949) 387-8500