City and County of San FranciscoDepartment of Building Inspection

Structural Subcommittee


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CODE ADVISORY COMMITTEE
 
Regular Meeting of the
Structural Subcommittee
 

DATE:

February 10, 2009 (Tuesday)

TIME:

9:00 a.m. to 11:00 a.m.

LOCATION:

1660 Mission St., Room 2031

 

This Subcommittee meets regularly on the second Tuesday of each month at 1660 Mission St., Room 2031. (DBI 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 1660 Mission Street, 2/F.  For information, please call David Leung at (415) 558-6033.


Draft MINUTES

 

Present

Absent

Jim Guthrie, S.E
Ned Fennie, A.I.A
Stephen Harris, S.E

 

Other Present

 Hanson Tom, DBI
 David Leung, DBI 

 

1.0     Call to Order and Roll Call.
Members: Jim Guthrie, S.E.; Chair; Ned Fennie, AIA.; Stephen Harris, S.E.


Meeting was called to order at 9:00 a.m.  Quorum established with 3 members present.

2.0     Approval of the minutes of the Structural Subcommittee special meeting of January 16, 2009.

Item 8.0 of the minutes was amended as follows:

“After code and regulation based on CAPSS were implemented, recommendations for other soft buildings may follow.”  was changed to:

“After regulations addressing these buildings are implemented, recommendations for other soft story buildings may follow.

A motion to approve the minutes as amended. Seconded and approved.

3.0     Discussion and possible action on draft CAPSS report.

SFBC Section 104H, with provisions on retrofitting the damaged building based on stiffness, was distributed in the meeting.

The soft story buildings in San Francisco that were targeted in CAPSS were 3 or more story wood frame building with 5 residential units or more and are located either on corner parcel, or  midblock with a gap between adjacent buildings on one or both sides of one foot or more at the top of the first story.

A research with computer analysis of a 4 stick model (based on CAPSS building no. 2) with 5%  damping and DBE spectra was presented.

DBE is pretty close to 1906 EQ, not MCE.

It was suggested to use 15% damping, to be less conservative and accounting for the damping effects of the crosswalls.

David Leung was assigned to pull surveys or drawings of around 10 buildings per CAPSS description.

For owners, 3 possibilities to mitigate the soft story:

  1. OK by engineer.
  2. Comply with some prescriptive measures (by DBI based on CAPSS), including plywood shearwalls, cantilever columns , or OMF with no brace.
  3. Comply with other design measure.


The approach to mitigate the soft story and the weak story by making the stiffness and strength ratio of the lowest floor equivalent to the upper floors was discussed.

The person at ATC responsible for the technical provisions in CAPSS will be invited to attend the next Structural Subcommittee meeting.

Possible allowance of encroachment to sidewalk for fixes were also discussed.

4.0     Discussion and possible action on 2007 SFBC Section 1604.11.3 to incorporate applicable provisions of 2001 SFBC Section 1605.4.3.

No discussion.

5.0     Discussion and possible action on 2007 SFBC Section 3403.2 to incorporate applicable provisions of 2001 SFBC Section 3403.2.1.1, exception 1.

No discussion.

6.0     Discussion and possible action on 2007 SFBC Section 3403.2.3.2.4 to incorporate recommendations of  SEAONC on repairs.

A revision on the SFBC on damage repairs based on SEAONC’s recommendations was proposed. This proposed revision will be formatted for further discussion and review by City Attorney.

7.0     Discussion and possible action on DBI’s Special Inspection Program.

No discussion.

 

8.0     Items 3.0 thru 7.0 are continued in next  meeting.

9.0     Public Comment:

Kevin Clinch, S.E. and BIC Commissioner, will be added to the distribution list.

10.0   Adjournment.

The meeting was adjourned at 11:00 a.m.