Structural Subcommittee
CODE ADVISORY COMMITTEE
Regular Meeting of the
Structural Subcommittee
DATE: November 6, 2002 (Wednesday)
TIME: 2:00 p.m. to 4:00 p.m.
LOCATION: 130 Sutter Street, Suite 600 (AIA Office)
This Subcommittee meets regularly on the first Wednesday of each month at 130 Sutter Street, Room 600. (AIA Office). If you wish to be placed on a mailing list for agendas, please call (415) 558-6205.
Note: Public comment is welcome and will be heard during each agenda item. Reference documents relating to agenda are available for review at the 1650 Mission Street, Suite 302. For information, please call David Leung at (415) 558-6033.
draft MINUTES
Present Excused Absent
Jim Guthrie, S.E. Michael Fretz, S.E.
Ned Fennie, AIA
Other Present
Pat Buscovich, S.E.
Hanson Tom, DBI
Yan Yan Chew, DBI
David Leung, DBI
1.0 Call to Order and Roll Call
Members: Ned Fennie, AIA; Jim Guthrie, S. E.
Meeting was called to order at 2:00 p.m. Quorum established with 2 members present.
2.0 Approval of the minutes of the Structural Subcommittee regular meeting of October 2, 2002.
A motion to approve the minutes as amended. Seconded and approved.
3.0 Public Comment: Public comment will be heard on items not on this
agenda but within the jurisdiction of the Code Advisory Committee.
Comment time is limited to 3 minutes per person or at the call of the Chair.
Hanson Tom expressed his appreciation that Ned Fennie did the road maps for the seismic triggering. For further clarification, Hanson Tom invited Pat Buscovich to look at some of the code sections that are not clear.
Pat said he has seen Ned’s flowchart and in his mind it is the clearest document of an unclear subject that can be written. The flowchart , as a road map, covers most cases but should not be distributed as the solution to every project because the code is much more complicated that just a road map. It should be used as an aid only by knowledgeable professional.
4.0 Discussion on SFBC Section 3403 on Seismic Triggering.
Section 3403.2.2.2 was discussed.
Pat has a major concern with this section because of the column issue that on a single-family residence, seismic is triggered on the entire house by removing a couple of columns for the garage. This requirement may be ludicrous. Initially, Pat intended to add an exception to this section for a single family house. Then later it was changed to read:
“When such alterations involve only the lowest story of a wood frame building
or structure and Section 3405 does not apply, only the lateral force resisting
components in and below that story need comply with Section 3403.6.”
Hanson Tom thought that the intent of the whole section on seismic triggering was to require the owner to do some kind of structural retrofit when the owner spend a lot of capital on the improvement projects. It is very clearly defined in this Section that a very simple removal of a column and adding a beam in a house would trigger seismic upgrade. In order to encourage people to house their car inside the garage and since the addition of a beam is not a major cost to the project, Hanson would like to add another exception (in addition to Pat’s exception as discussed above) saying that when you remodel a garage area by taking out the supporting columns and putting in the single beam, that will not trigger seismic retrofit.
Pat Buscovich said that last time there was a dollar threshold of $10,000.00 and if the work of taking out a column and putting back a beam in a single family
house was below the threshold , no seismic was required. However, this was not accepted by the Structural Subcommittee 5 years ago, not wanting to mix residential and nonresidential. The adopted compromise was that for
wood frame building or structure, when the alterations involve only the lowest story, only the lowest story need to be retrofitted. It can be any type of wood frame: residential, commercial, R-1 or R-3 and there was no more dollar threshold in this code section. Suggestion to revisit this section was discussed.
Giving R-3 a free ride was also suggested.
Both Pat and Hanson expressed concerns how this Section easily triggered seismic retrofit for the entire house by very minor work on upper floors.
Removal of the phrase “those areas tributary” in this Section was discussed.
Then this Section would say 30% of the vertical load carrying components
(joists, beams, columns, walls and other structural components). It would mean that if greater than 30% of the floor members were removed, it would trigger the seismic.
Removing the problemistic word column in this Section was also suggested.
Y. Y. Chew and Jim Guthie expressed concerns on the safety of the building.
Occasionally, removing of a column that is part of the frame may result in building collapse, since the lateral system was damaged. On the cost issue,
Y. Y. said that products such as Simpson Strong Wall significantly reduce
Seismic retrofit cost.
Pat Buscovich pointed out that buildings that fall down are the corner apartment buildings. There are very few R-3 corner apartment buildings. In light of this,
Pat suggested to give a separate exception. Wood frame exception per code as is; the corner apartment building would not qualify for the exception and thence
requires retrofit; and another exception that give R-3 a free ride(for the lowest
floor but not for the whole building). Picking a higher percentage for R-3 instead of 30% was also discussed. Hanson Tom suggested that Pat Buscovich could
write the language for further discussion.
Vulnerable buildings such as corner R-1 multifamily soft story buildings, ways to get them retrofitted (including point of sale triggers, property tax mandate, etc.) ,and what type of triggers were discussed. Hard data and CAPSS backup
would be required to justify these triggers.
Retrofitting these buildings was not just a private owner’s problem, but also a public policy probem because they provide low-income rent control housing, the Architectural context of the block and the neigborhood commercial. Whether it is in the juridiction of the Building Code to enforce a point of sale trigger was discussed, including the lack of basis under the City code of being more restrictive than the State code to require seismic retrofitting at point of sale.
There were vulnerable buildings not being captured by the current retrofit requirements. Hence the risk was identified but no fix was performed. The CAPSS program would provide the social and economic justification as an aid to the Board of Supervisors to mandate the public policy.
What to do with damaged buildings after an earthquake was also discussed.
In a moderate earthquake any damage at all on a concrete
frame building would indicate that it would not survive the big one. Thence any
damage in that frame building during a less than .2 earthquake should trigger a
seismic retrofit.
Without CAPSS , there was no hard data to demonstrate the need for the seismic retrofit. Scientific data that is recognized by FEMA and others were needed.
5.0 Subcommittee Member 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.
No new agenda item. Current item 4.0 will be continued in next regular meeting on 12/4/02.
No meeting in January, 2003.
6.0 Adjournment.
The meeting was adjourned at 4:00 p.m.