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Motivation and Development of PBEE for Existing and New Buildings PowerPoint PPT Presentation

Motivation and Development of PBEE for Existing and New Buildings William T. Holmes Structural Engineer Rutherford & Chekene Three areas of interest Retrofit of existing buildings Performance based codes (primarily new buildings) Broad view

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Motivation and Development of PBEE for Existing and New Buildings

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Motivation and Development of PBEE for Existing and New Buildings

William T. Holmes

Structural Engineer

Rutherford & Chekene

IRCC Workshop

October 18, 2006


Three areas of interest

  • Retrofit of existing buildings

  • Performance based codes (primarily new buildings)

  • Broad view

IRCC Workshop

October 18, 2006


Performance Based Seismic Design: Why the emphasis in the last decade?

  • The high cost of seismic retrofit, if done to comply with the prescriptive code requirements developed for design of new buildings,

    • may be too high for economic feasibility

    • may not provide the performance intended

  • Economic losses were higher than expected by owners due to both damage repair costs and business interruption in the Loma Prieta, and Northridge earthquakes (in this country).

IRCC Workshop

October 18, 2006


Phase 1 Project (1991-92)Identified major issues and recommended solutions

On Performance Goals (Issue 11.2):

Incrementalize and prioritize strengthening activities to the greatest extent possible. Identify the performance expectation of each increment.

Specify requirements for Life Safety, which would form the core of the Guidelines

Issues Identification and Resolution

FEMA 237: Issues ResolutionPredecessor to FEMA 273

IRCC Workshop

October 18, 2006


higher performance

Operational Level

Damage

Control

Range

Immediate

OccupancyLevel

Life Safety Level

Collapse Prevention

Level

Limited

Safety

Range

lower performance

Building Performance Levels from FEMA 273

1-A

1-B

Code for new buildings

3-C

5-E

IRCC Workshop

October 18, 2006


Performance Level

Serve as an effective

“Alternate Means”

For Equivalent Performance

Prescriptive Criteria Method

(Improve current code)

Introduction of Innovative Systems

For Superior Performance

Alternate to Prescriptions

Hazard Characterization

Traditional Performance Based Code Process Applied to Seismic Design

Performance Objective

Performance Requirements

Means of Verification

IRCC Workshop

October 18, 2006


Conclusions/Opinions Regarding Performance Based Codes

  • Near term use of performance based design concepts in codes will be:

    • tuning the prescriptive provisions

    • enabling development of “standards” for acceptance of new systems

    • Providing method to determine equivalence for “alternate means”

    • facilitating designs “over code” (voluntary)

  • Performance based design (at least using the detailed probabilistic methods, will not be the primary code method for a long time--if ever.

IRCC Workshop

October 18, 2006


A Broader View ofEarthquake Engineering

  • Design of New Buildings

    • Prescriptive “complete” method

    • Simplified methods

  • Individual Existing Buildings

    • Evaluation

    • Retrofit

    • Determination of expected losses

  • Groups of Buildings

    • Risk analysis

    • Economic portfolio analysis

    • Regional loss studies

  • Research and Reconnaissance

IRCC Workshop

October 18, 2006


Integration of all Uses

  • Groups Of Buildings:

  • Portfolio Analysis

  • Regional Loss Studies

  • Mitigation Studies

  • Building Rating Systems:

  • Probable Maximum Loss

  • Other

  • Individual Buildings:

  • Evaluation

  • Retrofit

Casualties

Repair Costs

Downtime

Percentage or Dollars

Performance Objective

IRCC Workshop

October 18, 2006


Integration of all Uses

  • Groups Of Buildings:

  • Portfolio Analysis

  • Regional Loss Studies

  • Mitigation Studies

  • Building Rating Systems:

  • Probable Maximum Loss

  • Other

  • Individual Buildings:

  • Evaluation

  • Retrofit

Casualties

Repair Costs

Downtime

Percentage or Dollars

Performance Objective

IRCC Workshop

October 18, 2006


Unified Performance System

  • Groups Of Buildings:

  • Portfolio Analysis

  • Regional Loss Studies

  • Mitigation Studies

  • Building Rating Systems:

  • Probable Maximum Loss

  • Other

Evaluation

Retrofit

Building Rating

Portfolio Analysis

Loss Studies

Mitigation Studies

Casualties

Repair Costs

Downtime

Means of Verification

IRCC Workshop

October 18, 2006


Interest and Demand from StakeholdersConsidering Broad Perspective

IRCC Workshop

October 18, 2006


Elastic Limit

Collapse

Base Shear Force

Displacement

IO

LS

CP

$, % replacement

25% 50% 100%

0

Casualty rate

0.0001 0.001 0.01 .25

0.0

Downtime, days

1 7 30 180

0

Needed Extension of FEMA 356 Concepts for Broader View

Performance Level

IRCC Workshop

October 18, 2006


Uncertainty is Big Issue

IRCC Workshop

October 18, 2006


Core of

“Performance Engine”

Extend over all ground motions

Consider uncertainty

P

M

Desirable Characteristics of the Verification Method

Ground Motion

Structural Response

Component and global damage level

Losses:

Casualties

Cost of Repair

Loss of use

Average Annual Loss

Cost Benefit Analysis

Death, Dollars, and Downtime

IRCC Workshop

October 18, 2006


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