HomeMy WebLinkAboutMiscellaneous Correspondence 1997-6-11
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MORTIER
ENGINEERING, P.c.
PO. BOX 139 . 1245 PEARL STREET
EUGENE. OREGON 97440
PHONE (541) 484.9080 . FAX (541) 484.6859
STRUCTURAL
BUILDING DESIGN. FIRE PROTECTION
CODE CONSULTANT. PLAN CHECKING
CONSTRUCTION INSPECTION
June 11, 1997
Jeff Philpott
Drake & Co.
91411 Coburg Rd.
Eugene, OR 97408
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R~: 5770 Mai~;:Sl Snrin!!field. - Structural Seismic Evaluation - W.O. #10058-ECM
As you requcstcd and we discussed at the site on Junc 10, 1997 I have observed the construction of
this building which was previously occupied'as the Albertson's Grocery Market. I understand that
thc building was constructed in approximately 1981 in conformance with the 1979 Oregon Structural
Specialty Code applicable at that time. This geographic area was located in seismic zone 2, based
on Figure] to Chapter 23 of that code. My observation of the construction is that it did comply with
scismic zone 2 dcsign criteria since I belicve that thc wind load design was probably the governing
criteria for latcralload transfer through thc building componcnts. Western Oregon is now placed in
seismic zonc 3 and since the 1979 Oregon Structural Specialty Code became effective on July I,
1980, the seismic load or base shear design has increased approximately 140%; therefore, I believe
that for some of the structural elements the seismic lateral load would govern rather than the wind
load.
You havc attempted to locate the original building plans. On June 10th I talked to Dave Pent,
Building Official of Springfield. He indicatcd that the plans may be available on microfiche in their
office. He will research this. My discussion with him indicated that he was not concerned with
seismic upgrading to the current code requirements, but wanted to be assured that any alterations
would not diminish the lateral load resisting capacity of the building. I informed him that I could
rcport on this aspect of the building condition and proposed a1tcrations. Without being able to rcview '
the original building plans, it is not possible to determinc the lateral load resistance capability due to
wind and seismic forces; however, I have every reason to believe that the design and construction
was in compliance with the code requirements in effect at that time. The building is of standard
construction and I am familiar with the construction of similar Albertson stores in Oregon. One
significant item relating to seismic design criteria is that the wood roof support ledgers connected to
the concrete block walls have load transfer steel angles extending the width of the ledger in order to
distribute the load and prevent cross grain bending which was a prominent failure factor in the San
Fernando valley earthquake of the mid-1970's. This code requirement was added in 1979 UBC. I
observed that the ledgers on all four walls have these load distribution angles. This indicates
compliance with the latest seismic design criteria applicable at that time. My discussions with Dave
Pent, Building Official, indicated that his concern was that the current alterations would involve
compliance with present code requirements relating to the new construction and that there would be
no downgrading of the expected structural performance. In this regard I noted the following items
which would be applicable to the alterations:
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1. The added interior partitions should be braced laterally at the top with diagonal braces
to the roof framing at the top chord of the open web truss joists. The attachment to
the suspended ceiling grid is not adequate lateral support. The support should be
provided with light gauge steel braces such as the steel studs used for the partitions
installed at approximately 45 degree angle connected to the top channel of the
partition and extended to attach to the top chord of a roof truss. These diagonal
braces should be installed in each direction at a maximum of 8 ft. intervals.
2. The suspended ceiling grid, if it is to be modified or extended, should have lateral
bracing in the areas where the modification or extension of the ceiling occurs. This
lateral bracing should be in accordance with the attached standard details.
3. Where soffit drops have been previously installed and partially removed, they should
be provided with adequate lateral support consisting of at least 2x4's installed at
approximately 45 degree angle from close to the bottom of the drop extended to the
top chord of the roof trusses at maximum 8 ft. intervals and nailed securely in place.
It may be the intent to remove these drops from the ceiling or modifY them in some
other way for the new tenant occupancy; therefore, they should be evaluated to
determine that they are adequately attached and supported for both vertical and
horizontal loads.
4. Other interior remodeling should not have an adverse structural effect or reduce the
structural load carrying capacity or resistance of the existing construction.
I hope this report is adequate for your purposes at this time. Please contact me if you have further
questions. Thank you for this opportunity to be of service.
Very truly yours,
Emile Mortier, P.E.
ECMlrc
Enclosure: detail
drake