DATE:

April 24, 2007 (Tuesday)

TIME:

9 a.m. to 11 a.m.

LOCATION:

1660 Mission St., Room 2039

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 304. For information, please call David Leung at (415) 558-6033.

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

Other Present:
Joe Maffei, Rutherford & Chekene
Mel Murphy, B.I.C.
Sahid Sattary, B.I.C.
Hanson Tom, DBI
Ray Lui, DBI
Howard Zee, DBI
David Leung, DBI

Absent:

   1.0

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

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 Subcommitteeregularmeeting of April 10, 2007.

The minutes was amended as follows:

4.0 Continue discussion and possible action on the following draft Administrative Bulletin: AB-083 on Guidelines for the Structural Review of New Tall Buildings
Delete the following sentence:

MCE check for deformation for collapse prevention (using time history and capacity design) appears to be more reliable than code based check for design level displacement.

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

   3.0

Discussion and possible action on proposed amendments on structural provisions to the 2007 California Building Code

No discussion.

   4.0

Continue discussion and possible action on the following draft Administrative Bulletin: AB-083 on Guidelines for the Structural Review of New Tall Buildings

The following documents are discussed:

(A)Case Study: Sample project:

1. Phase 1 Structural Calculations:
   DBE Step 1: Elastic (Response Spectrum) Analysis at DBE Level which is site specific scaled to Equation (30-6).
   Shear and flexural demands.
   This includes an analysis for 43 year event with reduced coupling beam stiffness. Shear demands are slightly less than code level.
2. Final Core Wall Design Verification:
   Nonlinear Time History Analysis at MCE level.
   Shear and Moment Design Verification
3. Supplemental Calculations:
   Impact to shear and moment demands due to varying amounts of flexural reinforcing in the hinge zone.
   This explores the amount of flexural reinforcing to produce possibly higher shear demands at top.

(B) Recommended Administrative Bulletin on the Seismic Design & Review of Tall Buildings Using Non-Prescriptive Procedures by SEAONC dated 4/23/07.

Ray presented (A) where he extracted some basic info from recent projects, to provide confidence levels for the process of establishing equivalency in gross terms such as overturning moments, etc.

Process of this Structural Subcommittee, performance objectives (to be stated or not), falling of cladding, extent of damage, coupling beams and serviceability evaluation requirements are discussed.

SEAONC will provide a comment log, listing all the previous comments on the AB Draft #2 and Task Force Action for review, as well as a blank comment form for further comments if required. It is more efficient for SEAONC to review if specific language is suggested.

Ray Lui will review (B) and prepare a list of DBI actions in response to (B), considering comments from Commissioner Sattary and others, and prepare AB-083 Draft #3 and submit to this Structural Subcommittee for review. Commentary (as discussion) to be embedded into AB.

   5.0

Continue discussion and possible action on the draft Administrative Bulletin:

AB-058 on Procedures for Seismic Instrumentation of New and Existing Buildings

This Administrative Bulletin was discussed in the Building Subcommittee of the Strong Motion Instrumentation Advisory Committee on 4/19/07 and was recommended by California Strong Motion Instrumentation Program, meeting their minimum requirements for installation and maintenance of seismic instruments.

At this time, the seismic instrumentation is still on a voluntary basis, since no public outreach has been made to alert the owners. About 6 buildings in the Building Occupancy Resumption Program have seismic instrumentation. Applicability to substantially altered buildings, the need for public outreach to the owners including BOMA for CSMIP to relate details of the required installation and maintenance of seismic instruments, memorandum of understanding between CSMIP and DBI for commitments of CSMIP for long term maintenance and owner obligations on size and location of rooms are discussed.

Questions on nature of space, power of connection including battery backup, specifications for equipments, maintenance of equipments, availability of access to data require answers from CSMIP.
CSMIP is invited to send a representative to the Structural Subcommittee meeting to explain the details of the required installation and maintenance of seismic instruments and obligations for the owners.

   6.0

Continue discussion and possible action on the draft Administrative Bulletin:
AB-085 on Guidelines for the Plan Check Review of Shoring and Underpinning

It is agreed to delete with the Department of Building Inspection from item 12 in draft #4 and add Details of the meeting shall be made available to DBI.

A motion to forward this Administrative Bulletin as amended to the Administrative Subcommittee and recommend to full CAC for possible structural approval. Seconded and approved.

   7.0

Items 3.0 and 4.0 are continued in next meeting.

   8.0

Public Comment

No public comment.

   9.0

Adjournment.

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