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Present:
Jim Guthrie, S.E.
Ned Fennie, A.I.A.
Other Present:
Joe Maffei, Rutherford & Chekene
Mark Moore, FE/Seismology
Steve Kuklin, Fifield Co.
Stephen Harris, SGH
Vahid Sattary, B.I.C.
Isam Hasenin, DBI
William Strawn, DBI
Laurence Kornfield, DBI
Hanson Tom, DBI
Ray Lui, DBI
Howard Zee, DBI
David Leung, DBI
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Absent:
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3.0
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Discussion and possible action on proposed amendments on structural provisions to the 2007 California Building Code
Basis of the amendments and assignments of review efforts were discussed.
In order to complete reviewing these provisions prior to July, it is recommended to have special meetings on the fourth Tuesdays each month, in addition to the regular meetings.
Public work session recommended.
Howard Zee to write to Doug Hohbach of SEAONC for help in Chapters 16 & 34.
Objective of this code cycle is to carry forward the intent of the current 2001 San Francisco amendments, without any changes. Changes can be made as supplements (every three months) after this code cycle.
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4.0
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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:
- AB-083 Draft #2 [prior to (B)]
- Recommended Administrative Bulletin on the Seismic Design & Review ofTall Buildings Using Non-Prescriptive Procedures by SEAONC
- Commissioner Sattarys letter to SEAONC on (B)
- Table of comparison between (A) and (B) by Ray Lui
Buildings over 240 ft. demand higher level of scrutiny since severe damage will pose undue burden to city resources.
Basic equivalency criteria, acceptance criteria, modeling analyses, scope issues (strictly seismic vs. all lateral), clarifications of assumptions and consistency, intent of publication, differences between other jurisdictions and San Francisco including near field and Peer Review requirements, task group objectives, quality assurance, , Structural Peer Review( may include wind design), serviceability checks provisions, ductility, collapse prevention vs. repairability, guidelines for R factors (explained in commentary) are discussed.
Repairability for a smaller earthquake and collapse prevention for higher earthquake are also discussed. Ground motions of MCE are assumed to be 1.5 higher than code level (DBE). Whether design intent for DBE is more conservative, or design intent for MCE more liberal are also discussed. 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.
This AB establishes the basic framework of intent of equivalent performance.
Engineer needs to establish and document that performance design to be equivalent to Prescriptive Design and to be reviewed by Peer Review Panels, Peer review is not a substitute for Plan Check (just for the equivalency between performance based and prescriptive), Ray Lui will incorporate (B) and (C) into (A) and submit to this Structural Subcommittee for review. Commentary (as discussion) to be embedded into AB.
Ray would also extract some basic info from recent projects, to provide confidence levels for the process of establishing equivalency in gross terms such as overturning moments, etc.
Separate Administrative Bulletins for Prescriptive Design of Tall Buildings, Peer Review, and Nontraditional Building Types (such as Base isolated Buildings) will be prepared by DBI.
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