ASCE Seismic Evaluation of Existing Buildings

Transcription

1 December 2010 PUC Meeting Summary Appendix D Briefing on the Effort to Update ASCE 31 and 41 Slide 1 Proposed Updates to ASCE 31 and 41 A Mid-cycle Snapshot Update for the BSSC PUC December 7, 2010 Washington, DC Bob Pekelnicky Vice-Chair and Secretariat Slide 2 ASCE Seismic Evaluation of Existing Buildings ASCE Supplement No. 1 Seismic Rehabiliation of Existing Buildings

2 Slide 3 ASCE 31 & 41 Updates 2013 Target to Issue Update Steering Committee Chris Poland Chair Bob Pekelnicky Vice Chair/Secretariat Brian Kehoe Peter Somers Subcommittees ASCE 31/41 Combine/Streamline Peter Somers ASCE 31 Update Brian Kehoe ASCE 41 Update Bob Pekelnicky Slide 4 Short & Long Term Issues Slide 5 Committee Schedule Target 2013 Q White Cover Edition 2010 Focus: Checklists & 31/41 Combine/streamline 2011 Focus: ASCE Focus: Balloting / Resolution Q3/Q Public Comments Quarterly Meetings

3 Slide 6 All material presented herein is in-progress and subject to change based on committee balloting Slide 7 Combining ASCE 31 & 41 Prescriptive (T1 & T2) & Systematic (T3/41) One set of General Provisions Tier 1 will be set-up to stand alone Deficiency only T2 Points to ASCE 41 m-factors Full-building Tier 2 replaced with linear ASCE 41 Slide 8 Tier 1 Updates Benchmark Building checklist One General Building Checklist Supplemental Checklists based on building type Set of checklists only for Life Safety Supplement Checklists for Immediate Occupancy Nonstructural Checklists for LS and IO coinciding with the redefinition of NS performance.

4 Slide 9 ASCE 41 Issue Teams General Provisions / Seismic Hazard - Bob Pekelnicky Analysis Mark Moore Concrete Ken Elwood (Coord with ACI 369) Steel Charles Roeder (Coord with AISC TC-9) Timber Phil Line Masonry John Kariotis Geologic John Egan Material Testing Mike Braund / Mike Mayes Consistency & Clarifications Chris Tokas Slide 10 General Provisions Updates Alternate Seismic Hazard Paths Code Equivalent Performance Objectives Existing Building Increased Risk Objectives Updated Levels of Seismicity Revised Nonstructural Performance Levels Slide 11 Code Equivalent Performance BSE-2: ASCE 7-10 MCE R BSE-1: (2/3) * MCE R Table Tying Occupancy (Risk) Category to Structural & Nonstructural Performance for both BSE-1 & BSE-2 Hazards Occupancy / Risk Category BSE-1 BSE-2 I & II S-LS / NS-LS S-CP / NS-NC III?? IV S-IO(?) / NS-OP (?)?

5 Ratio Ratio Slide 12 Higher Risk Objectives BSE-2R 5% in 50 year probabilistic Mean deterministic cap 50% of BSE-2 floor BSE-1R: 20% in 50 year probabilistic 50% of BSE-1 floor Retain Basic Safety Objective & other ASCE 41 performance objectives Slide 13 5/50 vs. MCE R 5%-50yr MCE R Note: no deterministic cap Southern California Northern California Pacific NW Intermountain CEUS City Sequence # Slide 14 20/50 vs. (2/3)*MCE R 20%-50yr ( 2/3 x MCE R ) Southern California Northern California Pacific NW Intermountain CEUS City Sequence #

6 Probability of Collapse in 50yrs Probability of Collapse in 50yrs Probability of Collapse in 50yrs Slide 15 Collapse Risk MCE R MCE R Southern California Northern California Pacific NW Intermountain CEUS City Sequence # Slide 16 Collapse Risk 0.75* 2% in x 2%-50yr Southern California Northern California Pacific NW Intermountain CEUS City Sequence # Slide 17 Collapse Risk 5% in 50 5%-50yr Southern California Northern California Pacific NW Intermountain CEUS City Sequence #

7 1-Second Short-Period Slide 18 Collapse Risk Summary Region MCER 0.75 x MCER 0.75 x 2%-50yr 5%-50yr Southern California 1.2% 2.4% 1.8% 2.2% Northern California 2.1% 4.1% 2.4% 2.3% Pacific Northwest 1.0% 1.9% 1.7% 2.0% Intermountain West 1.0% 1.7% 1.4% 2.1% CEUS 1.0% 1.5% 1.3% 2.1% Weighted Mean 1.2% 2.1% 1.6% 2.1% Region MCER 0.75 x MCER 0.75 x 2%-50yr 5%-50yr Southern California 1.2% 2.3% 1.8% 2.2% Northern California 1.7% 3.3% 2.2% 2.2% Pacific Northwest 1.0% 1.8% 1.5% 2.0% Intermountain West 1.0% 1.8% 1.6% 2.1% CEUS 1.0% 1.6% 1.3% 2.0% Weighted Mean 1.1% 2.0% 1.6% 2.1% Slide 19 Level of Seismicity Revisions Match ASCE 7-10 Seismic Design Categories Very Low Low Moderate High = SDC A (New Category) = SDC B (Revision) = SDC C (Revision) = SDC D, E, & F Goal is to remove inconsistencies Slide 20 Nonstructural Performance Level Redefinition Life Safety Actual documented past cases of causing death, serious injury, or egress disruption in major earthquakes. Position Retention / Immediate Occupancy Element has not moved or become unbraced/unanchored, but may not be functional. Operational Element has been certified or designed to retain position and be resilient such that it can immediately return to operation.

8 Slide 21 Analysis Short Term How to determine m-factors and backbone curves Incorporate FEMA P440a material Update foundation rocking J-factor Add broad response history analysis criteria (number of records, scaling, etc.) Address how force controlled components can be modeled in NDP Expand/rewrite the protective systems chapters Incorporate ATC 76-6 results (relax LDP and CMP) Reconcile pushover and response spectra approach with max direction spectra. Slide 22 Geologic Issues Create performance based liquefaction provisions Provide guidance on hazard to evaluate liquefaction Provide guidance on structural consequences of differential settlement, lateral spreading and bearing loss Slide 23 Material Testing Issues Revise Usual Testing Requirements for Kappa = 1.0 Review and update testing requirements for all materials Long Term Revise Kappa Factor to be based on action / consequence dependent Update testing requirements for all materials

9 Slide 24 Concrete Update ASCE 41 based on balloted changes in ACI 369. Including: o o o Changes to connector provisions (removal of 0.5 factor for cracking). Referencing to ACI material and condition assessment documents. Editorial and minor organizational changes. No Update to Shear Wall m-factors this cycle without funded effort Slide 25 Steel Issues Add BRBF information Add acceptance criteria for braced frame gusset plates acting as moment connections. How to deal with braced frame beamcolumn moment connections w/ gusset plates Verify the moment connection rotation limits In general update references to the latest AISC manual, currently referencing AISC LRFD Slide 26 Wood / Light Frame Update to 2005 NDS & 2008 SDPWS Dealing with existing connectors Default strength and stiffness values for wood diaphragms Adding separate provisions for Coldform steel a Long Term issue

10 Slide 27 Masonry Issues Incorporate ASCE 31 special URM procedure into ASCE 41 Nonlinear URM Provisions need review All In-fill provisions updated Update Reinforced Masonry