DATE:

May 13, 2008 (Tuesday)

TIME:

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

LOCATION:

1660 Mission St., Room 2031

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.

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

Other Present:

Doug Woods, CAL/OHSA
James McCarthy, CAL/OHSA
Pat Buscovich, PBA S.E.
Ray Lui, DBI
Rick Halloran, DBI
Dan Lowrey, DBI
Hanson Tom, DBI

David Leung, DBI

Absent:
 


 

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 regular meeting of April 8, 2008.

The minutes will be amended as follows:

           “…..concrete core strength prior to placing of tie-back anchor bolts(caution to

           avoid cutting tendons in PC slab)…”    will be changed to :          

           “…..concrete core strength prior to placing of tie-back anchor bolts(caution to

           avoid cutting tendons in PT slab)…” 

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

3.0

Discussion and possible action regarding a proposed ordinance (File No. 080281, Peskin) amending the San Francisco Building Code by adding Sections 106A.4.1.4 et.seq. to establish the Slope Protection Act and create procedures that require the Structural Advisory Committee to review and make recommendations on specified permit applications for all property within the City that exceeds an average slope of 25% grade, and to require mandatory denial of the permit by the Building Official under specified circumstances; amending Section 105A.6.2 to specify the composition of the Structural Advisory Committee for permit applications subject to the Slope Protection Act; amending Building Code Section 106A.3.2 to require that the applicant for certain permit applications subject to the Slope Protection Act provide substantial documentation that there exists sufficient infrastructure to support the proposed residential development and that the proposed emergency access routes meet standards in effect at the time of the application; amending Building Code Section 1701A.5 to require special inspections throughout the construction process for sites subject to the Slope Protection Act.     

Copies of the proposed ordinance are distributed.

San Francisco already has Structural Bulletin SB 01-08 in place, which requires submission of soils investigation reports for all new buildings and horizontal and/or vertical additions to existing buildings within the landslide zones. There seems no need for further ordinance or regulations required.

Problems of slope stability are not clearly identified in the ordinance. Even if slope stability is a concern, there may be a smoother way (such as structural design review) to address it than this ordinance, which imposes immense finance burden for SAC requirements on building owners of SF.

Concern that the slope of 25% grade seems to have no technical basis.

Geotechnical expert to weigh in on this issue is lacking. 

Motion to strongly oppose to this proposed ordinance and forward this statement of strong opposition to full CAC. Seconded and approved.

4.0

Discussion and possible action on AB-023: Tower Crane Site safety Plans

Concerns about the continuity of high level CAL/OHSA oversight and that when Doug and James retires, loss of knowledge and loss of oversight are discussed. This is prevented by Doug and James developing good Crane procedures and good guidelines in Title 8 mandatory for everybody to  follow.

Three elements of crane procedures:

(1)  Loads: Crane engineer will stamp plans and calc. for these loads. Crane engineer will also provide spec of bolts, plates and brackets required.

(2)  EOR will review the adequacy of the floor slab to take the loads including torque, shear, etc.  when the crane is tie-in to the building and will put in review stamp after confirmation that the foundation is able to take the loads, and that the bolts and washers are adequate.

(3)  Special Inspector will verify that slab is ready and installation is proper: e.g. that edge distances, emdedment etc. and concrete core strength are adequate.  Oversight of connections and crane foundations to be ready and anchors to be installed properly will be included in AB.

CAL/OHSA issues erection permit and operation permit after verifying that crane meets ANSI requirement and load lest requirement after review. These permits may not be ready when applicant apply building permit from DBI.

DBI requires evidence that  applicant  already applies for erection and operation permits from CAL/OHSA. DBI also requires crane location plan, operation radius, special inspection for the anchors and the anchorage to the foundation for operation. Structural observation may not be needed. DBI will also check qualification of special inspector.

Policy of  requiring letter of consent from neighbors for permission to swing over the loads (not the boom) need to be included in AB.

Action item is to revise AB-023 to incorporate CAL/OHSA recommendations and to return to this subcommittee for review.  Then, mobile cranes (and foundation permit ) will be discussed in this subcommittee.

5.

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

(1)  In moving to the present 2007 SFBC Section 1604.11.3, the following provisions of 2001 SFBC Section 1605.4.3 were removed:

1. “Near field effects (N_a and N_v of Tables 16-S and 16-T) and the reliability/redundancy factor (P) need not exceed 1.0; and
   
   
2. The load factor resulting from the vertical component of the earthquake ground motion(E_v) may be 0; and
   
   
3. Fifty percent of D_m may be used to evaluate deformation compatibility of existing elements and existing exterior elements in accordance with Section 1633.2.4; new elements shall meet the full criteria of this code; and
   
   
4. The maximum allowable height-to-length ratio for shear resisting construction with wood frame may be taken as 3.5; and
   
   
5. In wood frame buildings not more than 4 stories in height, R may be 5.5 regardless of the bracing system or materials used.”

When the R=5.5 is removed, there is no R value for use for combination plywood, gypboard and steel frame. The default value of R=2 may be too conservative, with increase in base shear of 200%, which may not be warranted for wood building. It is noted that ATC-63 (Quantifications of Building System Performance and Response Parameters) uses R = 3 for OMF.

It is recommended to re-instate R = 5.5 or some reasonable value for wood frame building up tp 4 stories, possibly with  exception to go to R = 3.5 for wood shearwalls on top of OMF in  the lowest  level, through Structural Bulletin or Code Interpretation.

(2)  It is recommended to draft an AB for new wood frame building to provide guidelines on pounding, drift and if building requires setback.  A block without uniformity may create pounding probems.

(3)  Report and Recommendations from SEAONC’s SFBC Structural Damage repair Study Group was distributed.
Further discussion and possible action awaiting  official SEAONC approval.

6.

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

No discussion.

7.0

New agenda items: discussion and possible action on pounding and setback for wood frame building and discussion and possible action on SEAONC recommendations on structural damage repair will be added.

Items 4.0 thru 6.0 are continued in next  meeting

8.0

Public Comment

No public comment.

9.0

Adjournment.

The meeting was adjourned at 10:50 a.m.