|
1.0
|
Call to Order and Roll Call
Members: Jim Guthrie, S.E.; Chair; Ned Fennie, AIA; Michael Fretz, S.E.
Meeting was called to order at 9:00 a.m. Quorum established with 2 members present.
|
|
2.0
|
Approval of the minutes of the Structural Subcommittee Regular meeting of November 5, 2003.
A motion to approve the minutes. Seconded and approved.
|
|
3.0
|
Continued discussion and possible action on exception from Special Inspection requirements for signs and awnings.
Awaiting for Hanson Tom to go back to the people who requested this clarification for certain weight and size in minor projects on a case-by-case basis.
|
|
4.0
|
Continued discussion on Trichapter Uniform Code Programs.
This item will be re-named as “Continued discussion on Updates to Structural Standards in 2001 California Building Stds. Code”.
Some jurisdictions of the South Peninsula Trichapter of ICBO did actually adopt these California Amendments.
Concerns on the provisions that change the height limit of steel ordinary braced frame from 160 feet to 35 feet are discussed. The 35 feet limit is quite arbitrary. This provision affects many of San Francisco buildings that are 5 –story (or even 4 –story) that are over 35 ft. Looking at citywide big picture there is a demand for buildings that are 40 – 50 ft in height, which may be seriously affected by this provision. Narrowing the application to a two-tiered approach with consideration to occupancy groups or construction types or soils conditions was also discussed.
DBI’s preferred approach is to wait for the State to adopt these California Amendments and then adopt or amend it into the San Francisco Building Code.
Weakness of the steel ordinary braced frame was also discussed, including concerns on development of a story mechanism, lack of secondary system, buckling and fractured connections.
Since adopting these California Amendments is a substantial change to San Francisco Building Code, it is recommended that a public hearing to be held in which everybody is invited, prior to moving it forward to the full committee. For substantial change like this, the Board of Supervisor often asked what has been done to outreach the public on this subject.
Question is raised on what is the official position of SEAOC on these California Amendments.
|
|
5.0
|
Continued discussion on and possible action on preliminary results of CAPSS Program.
In order to address and find a strategy for code amendment mandate, the issues of CAPSS are briefly summarized.
The CAPSS work on analysis of CAPSS survey data was stopped at about 95% completion. Justification for payment and documentation on expenses are still currently being reviewed. Since the contractor, Applied Technology Council , has not been paid, further work is not possible. Dan Shapiro showed interest to continue even if this is not a City funded project. Some data are available, but a plan or strategy is never produced, nor are feedbacks and comments on how to make the plan work.
Of all buildings in San Francisco that are vulnerable in a seismic event, the older (say, pre-70s) wood frame corner commercial/residential buildings in liquefaction zone may be of the greatest impact to the City economy, since the neighborhood commercial and affordable housing may not be maintained upon an earthquake occurrence. If only a small group of buildings (such as pre-70 wood frame corner commercial / residential buildings in liquefaction zone with soft story) is focused on, it is easier for a legislation requiring an seismic upgrade to pass.
Whether the wood corner buildings in liquefaction zone are worse than the wood corner buildings anywhere else is also discussed.
Various triggers for seismic retrofit are discussed. One of the current trigger is in Section 3403.2.2.3 : “A buiding or structure shall be considered to have sustained structural damage when the vertical elements of the lateral force resisting system in any story, in any direction and taken as a whole, have suffered damage such that the capacity has been reduced by more than 20 % from its predamaged condition. A structure shall be considered to have sustained structural damage when the vertical load components supporting more than 30 % of the structure’s floor or roof area have suffered a reduction in vertical load carrying capacity such that they are required to be either structurally repaired or replaced in order to comply with this code.” Clarification on this trigger with clear definition of damaged building and what constitutes the 20% (and 30%) in this Section is required, to avoid potential arguments and lawsuits after future earthquake . Such clarification would be part of the future CAPSS’s work in Phase 3, if the program is re-activated. The work may include a little matrix of how much the ground motion was versus what the damage was and to develop a description of damage state instead of the percentage. Post-earthquake retrofit methods are also discussed.
Options on voluntary seismic upgrade to work on the lower floor only, and incentives to owners are discussed . There are concerns that additional braces may produce a higher stress in the second floor than before.
Revision of Planning Code Sec. 188(b) to disallow the following if the building is not seismically retrofitted is also discussed:
|
|
|
|
“A noncomplying structure that is damaged or destroyed by fire,
|
|
|
or
|
|
|
|
|
other calamity, or by Act of God, or by the public enemy, may be restored to its former codition: provided that such restoration is permitted by the building Code, and is started within one year and diligently prosecuted to completion.”
|
|
6.0
|
Continued discussion on DBI requirements for geotechnical reports.
Awaiting for Zan Turner to prepare a draft administrative bulletin to clarify DBI’s requirements for geotechnical reports, which is currently reviewed by Laurence Kornfield and Hanson Tom.
DBI currently tries to locate some research work done in Southern California and possibly adopt standardized procedure based on this work.
|
|
7.0
|
Subcommittee Member’s and Staff’s identification of new agenda items, as well as current agenda items to be continued to another subcommittee regular meeting or special meeting. Subcommittee discussion and possible action regarding administrative issues related to building codes.
Current items 3.0 thru 6.0 will be continued in the next meeting on Wednesday, January 7, 2004 from 9:00 a.m. to 11:00 a.m. at DBI, 1660 Mission Street.
|
|
8.0
|
Adjournment.
The meeting was adjourned at 10:45 a.m..
|
