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RE: Seismic Question

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Paul,
Thank you for replying to Rich with such a complete answer. Your
response was very important in the state of California as well as other
Pacific Rim states (not to mention areas in Utah and Arizona which are
taking a more serious approach to unreinforced masonry and concrete
structures with inadequate ledger connections to the diaphragms).

These older buildings serve a purpose despite the fact that they are and
will remain hazardous structures. The purpose of codes like the UCBC
Appendix Chapter One is intended to maintain the structural integrity of
the building long enough to get people out. Buildings that were retrofit
have historically done well as was evident in the Los Angeles area,
which started their retrofit programs as early as Division 68 in the
early 80's and which led to the development of City of Los Angeles RGA
1-91 that, with modifications, ultimately became the Uniform Code for
Building Conservation (UCBC) Appendix Chapter 1.

I am negotiating with a local city to retrofit some of their buildings
now and their public works department is going through the same
discoveries as others cities have done to understand that retrofit URM
buildings continue to serve the community by providing affordable
housing (usually low income housing) as well as affordable commercial
sites in Empowerment Zones (Federally supported business sites) and
Zones that serve State and Local zones. Furthermore, retrofits preserve
historic sites. 

While nothing can be promised of these buildings, their performance has
been more than acceptable. Comparatively, the city of Santa Monica
enacted their retrofit ordinance after the Northridge Earthquake as the
building owners associations vehemently fought any attempt to make
retrofit mandatory. The state only required the identification of
hazardous buildings by a certain year, but left the ordinance to require
retrofit up to each municipality. Poorer communities like those in the
Inland Empire (Riverside and San Bernardino Counties) delayed retrofit
ordinances and still do not have one in place. There is no logical way
to force an owner to retrofit a building when lenders are not willing to
make loans to these owners.

I designed two specific buildings in Santa Monica. The first was the
First Christian Church on Fifth and Arizona that is no longer there. The
Church was able to obtain enough money to retrofit the first floor with
anchorage. After the Northridge earthquake, the building had to be
demolished, but not until all of the homeless who slept in the basement
level were safely removed from the building. This was a historic site
and they Church elders were unable to obtain financial loans or
donations necessary to even phase the retrofit to get the anchors in
place.

The second building was another beautiful building on Fourth and
Broadway that included a four story tower on the corner of Forth street
across from Santa Monica Place. The building was owned by an 85-year old
lady who wanted to retrofit the building, but who maintained rents in
the building for many years. An Architect by the name of Bill Brantley
rented a portion of the second floor and acting as the representative
for the elderly lady hired me to prepare the retrofit plans. One
particular area at the tower consisted of cast in place concrete
figures. The first level had been remodeled numerous times since 1929
and layers of paint kept the building from fitting into the
neighborhood.

The Architect returned the appearance of the building back to the 1929.
Unfortunately, the owner was denied loans by local banks and the damage
from the Northridge earthquake tripled the cost of the retrofit by
adding repairs to the building. The contractor did a poor job and was
removed from the job and replaced by the Architect who acted as the
owners representative to do an owner-builder retrofit and remodel. I am
pleased to say that the building is now returned to it's original
appearance back in the twenties and it looks beautiful. It was difficult
to move the cast in place concrete panels back into place and retrofit
them to the interior structure with hopes that they will not shift in
the next similar quake. 

There is no guarantee as to the future of these building, but the
retrofit programs do work and new technology is improving on the work we
did in the 80's and early 90's working for the SEAOSC Existing Building
Committee (known then as the Hazardous Buildings Committee). I think a
lot of the credit goes to the founders of the ABK method who includes
Barnes, Kariotis and the "A" I can only guess as Abaginian (please
correct me Nels and Mike who I know are very familiar with this
document). I think if new construction were designed based on the
assumptions that led the ABK method to identify interior walls as
dampers, thus lowering the need for Rho depending on the aspect ratio of
the walls (3.5:1 at the time), then a more reasonable design methodology
could have been devised that would have produced a less complicated
method of design of new buildings.

Dennis S. Wish, PE

-----Original Message-----
From: Paul Feather [mailto:pfeather(--nospam--at)SE-Solutions.net] 
Sent: Tuesday, October 15, 2002 9:14 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Seismic Question


Rich,

I am going to ask that you restate your question with greater clarity
regarding what exactly you are having an issue with.

It is not my intent to be rude, but on my initial reading of your
request I am absolutely astonished that anyone using the title
Structural Engineer would ask such a basic general question "how do I
perform a lateral analysis of a concrete structure".  If you have no
experience with building systems there is no way anyone on this list can
provide a 3 step lesson on lateral design and rigidity analysis.  I
would suggest you hire a qualified consultant.

Additionally, if the building is 50 years old, I think you will find the
existing structure woefully inadequate vertically and laterally for
support of an additional level of concrete framing.  You should expect
substantial modification and upgrade of the existing systems.  There is
a world of difference between a life safety retrofit for continued use
of an existing building and current code compliant retrofit and remodel
of an existing building.


Paul Feather PE, SE
pfeather(--nospam--at)SE-Solutions.net
www.SE-Solutions.net
----- Original Message -----
From: "Richard Mullen" <rmullen(--nospam--at)damianolong.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Tuesday, October 15, 2002 6:16 AM
Subject: Seismic Question


> We are currently rehabing a 50 year old reinforced concrete building 
> supported by timber pile foundations.  The building is currently three

> stories in height and is proposed to be four stories when constructio 
> is complete. How do you distribute seismic forces in the horizontal 
> direction to the columns, diaphragms and shear walls for this 
> reinforced concrete
three-story
> building?  Also how do you calculate the later stiffness of this 
> building?
>
> Rich Mullen
> Structural Engineer
> Damiano Long LLC
> (856) 225-9300 Fax (856)
> e-mail rmullen(--nospam--at)damianolong.com
>
>
>
>
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