Seismic Safety, Risk Reduction and Performance-Based DesignAimed at Nuclear Facility Structures

Bozidar Stojadinovic, Associate Professor

Department of Civil and Environmental Engineering

University of California, Berkeley

Outline

What is performance-based design?How to design structures to reduce risk? What are the safety-increasing innovations in structural engineering?Why should we do this for the new nuclear cycle in the US?

Performance-Based Design

Design to achieve specified results rather than to adhere to particular technologies or prescribed means(Moehle, EERI Distinguished Lecture,

2005)

Directly address the needs of the owner or user of the system or structure in their risk environment

Prescription vs. Performance

A code provision (ASCE 43-05: 6.2.2(a)):

“Minimum joint reinforcement shall consist of X-pairs of #4 diagonal cross-ties spaced 12 in. on center.”

Prescription vs. Performance

What is the performance? Is such joint safe? If so, what is the level of safety? If so, how much does it cost to be so

safe? Would #3 cross-ties spaced 6 in. on

center be better or worse? Safer? Less expensive? Easier to build?

Performance-Based Design:Earthquake Engineering View

Prof. Mahin, CEE 227 Lectures

Performance-Based Design:Deterministic Quantification

Prof. Mahin, CEE 227 Lectures

Performance-Based Design:Probabilistic Quantification

Prof. Mahin, CEE 227 Lectures

How to Design for Performance?

Prof. Mahin, CEE 227 Lectures

Probabilistic Framework

Performance-based Evaluation Example :How Safe are our Bridges?

Type 1 Type 11

Framework for Bridge Evaluation

Engineering Demand Parameter (EDP)

Inte

nsit

y M

easu

re (

IM)

Engineering Demand Parameter (EDP)

Dam

ag

e M

easu

re (

DM

)

discrete

continuous

Decision Variable (DV)

Dam

ag

e M

easu

re (

DM

)

discrete

continuous

Decision Model

Damage Model

Demand Model

Hazard Model

0 . 1 1 1 0 1 0 0 1 0 0 0Distance (km )

4

5

6

7

8

Mag

nit

ude

0 . 1 1 1 0 1 0 0 1 0 0 0Distance (km )

4

5

6

7

8

Mag

nit

ude

Select and scale ground motions

Engineering Demand Parameter (EDP)

Inte

nsit

y M

easu

re (

IM)

Engineering Demand Parameter (EDP)

Dam

ag

e M

easu

re (

DM

)

discrete

continuous

Decision Variable (DV)

Dam

ag

e M

easu

re (

DM

)

discrete

continuous

Decision Model

Damage Model

Demand Model

Hazard Model

CL

Do non-linear time-history

analyses

Framework for Bridge Evaluation

Framework for Bridge Evaluation

Engineering Demand Parameter (EDP)

Inte

nsit

y M

easu

re (

IM)

Engineering Demand Parameter (EDP)

Dam

ag

e M

easu

re (

DM

)

discrete

continuous

Decision Variable (DV)

Dam

ag

e M

easu

re (

DM

)

discrete

continuous

Decision Model

Damage Model

Demand Model

Hazard Model Performance(damage)

states

Framework for Bridge Evaluation

Engineering Demand Parameter (EDP)

Inte

nsit

y M

easu

re (

IM)

Engineering Demand Parameter (EDP)

Dam

ag

e M

easu

re (

DM

)

discrete

continuous

Decision Variable (DV)

Dam

ag

e M

easu

re (

DM

)

discrete

continuous

Decision Model

Damage Model

Demand Model

Hazard ModelDeaths?Dollars?

Down-time?

Outcome: Repair cost ratio

fragility curves

Framework for Bridge Evaluation

Demand Model

Sa(T1)=1g

Common Probabilistic Basis for Civil and Nuclear Structures

Given a seismic hazard environment and a structure, the probability that a performance objective is achieved is:

Consider probability distributions of seismic hazard, of demand and of capacity due to: Lack of knowledge (epistemic uncertainty) Record-to-record ground motion randomness

(aleatory uncertainty)

hazard

PO hazarddhazardPOPP )()|(

Seismic Hazard and Probability of Failure

Hazard: probability of exceeding a value of ground motion intensity (hazard curve)

Failure: a comparison demand and capacity

0( ) ( )H HP P kH a aP H s k s

( ) ( ) ( )a

F a a

s

P P C D P F s dH s

DOE-1020 and ASCE 43-05:(Nuclear) Acceptance Criteria

Probability of failure is smaller than probability of hazardRisk reduction ratio at the structure level

HR

F

PR

P

Performance Category Risk Reduction Ratio

PC-1 (conventional) RR=1.0

PC-2 (internal exposure risk) RR=1.0

PC-3 (labs, fuel cycle facilities)

RR=10.0

PC-4 (experimental reactors) RR=20.0

Conventional Design:Acceptance Criteria

Probability of failure is, implicitly, assumed equal to the probability of hazardDesign equation: Capacity reduction Demand amplification

at the structural element level

HF PP

DC

CommonRisk-Informed Design Framework

Hazard vs. Failure

Conventional Structures Nuclear Facility Structures

FH PP FH PP

Design Equation

b

kR

CD

R

Common Risk-Informed Design Framework

New nuclear power plants can be designed using a risk-informed performance-based frameworkModels for most elements of the structure exist, including aleatory and epistemic uncertaintiesModeling can be extended to:

Other extreme hazards (natural and man-made) Ageing effects (construction and maintenance) Accidents (effects on the environment and society)

Risk-based evaluation is used for some aspects of the nuclear fuel cycle design today

Innovations in Civil Engineering(DOE NP2010 Initiative)

Over the past 30 years civil engineering did not stand still: Technologies ready for deployment New and promising technologies

worthy of additional exploration and development

Note: this is just the CE side! No NE-CE-ME synergies were explored

Ready-to-Use CE Technologies

Response modification devicesSteel-plate sandwich structuresAdvanced concrete admixturesComposite plastics for reinforcementPipe bends vs. welded elbows

Precision blasting for rock removal High-deposition rate and robotic weldingCable splicing4-D modeling and BIMGPS use in constructionOpen-top installation

Upcoming CE Technologies

Prefabrication, preassembly and modularizationAdvanced information management and control during design and construction

Earthquake Engineering of Heavy Structures

Large weight, often positioned high above the foundationCombat inertia forces through: Strength Flexibility Damping

Reactor Cavity Cooling System

Reactor Pressure Vessel

Control Rod Drive Stand Pipes

Power Conversion System Vessel

Floors Typical

Generator

Refueling Floor

Shutdown Cooling System Piping

Cross Vessel (Contains Hot & Cold Duct)

35m(115ft)

32m(105ft)

46m(151ft)

Steel-plate Sandwich Walls

Steel plate used as: Form Reinforcement

Steel-plate Sandwich Walls

Steel plate used as: Form Reinforcement

Composite action with concrete enabled using studs

Steel-plate Sandwich Walls

Steel plate used as: Form Reinforcement

Composite action with concrete enabled using studsLimited damage

Steel-plate Sandwich Walls

Steel plate used as: Form Reinforcement

Composite action with concrete enabled using studsLimited damage

Steel-plate Sandwich Walls

Steel plate used as: Form Reinforcement

Composite action with concrete enabled using studsVery strongVery ductilie, too!

Steel-plate Sandwich Walls

Steel plate used as: Form Reinforcement

Modular, prefabricated componentsRapid construction

Response Modification Devices

Devices designed to alter dynamic response of structures: Base isolation, to

reduce input motion/energy

Added damping, to dissipate energy that enters the structure

Base Isolation Concept

Provide a soft, deformable layer between the structure and the groundNot new! Sanjusangendo

Temple in Kyoto, built in 1164

Base Isolation Concept

Base Isolation Benefits

Reduced motion of the structureReduced acceleration of the content

Base Isolation Benefits

Reduced motion of the structureReduced acceleration of the contentProblems: Vertical

acceleration Seismic gap Crossing the gap

Base Isolation Benefits

Reduced motion of the structureReduced acceleration of the contentProblems: Vertical

acceleration Seismic gap Crossing the gap

Base Isolation Devices:Laminated Rubber Bearings

Technology developed in 1980’sUsed in non-nuclear but safety-critical structures: LNG tanks Hospitals Emergency

command centers

Base Isolation Devices:Friction-Pendulum Bearings

Technology developed in 1990’sUsed in conventional building structuresUsed in critical infrastructure: Bay Area long-span

bridge crossings Off-shore platforms

Steel damper

Lead damper

Oil damper

Friction damper

Response Modification Devices: Seismic Dampers

Why Design Based on Performance?

Integrate the entire nuclear fuel cycle design to enable transparent risk-informed decisions on: Safety Security Economy Effects on the environment

(sustainability)

Safety, Security, Economy and Sustainability

Use simulation to evaluate effects of hazards: Anticipate before we build them

Balance safety and economy: Do what is necessary, no more, no less Find the sweet spots where small investments

result in significant benefits

Integrate security and sustainability: Design right from the get-go Reduce carbon emissions during construction,

too! Be modular, reuse and recycle

How Do We Get There? A unique opportunity is here: A new building cycle is starting There is little institutional memory left:

Bad: there is no experience Good: there is no experience!

Form cross-disciplinary engineering teams as early as possible: State performance objectives, not

prescriptions Work together to formulate the design

process and execute it right!

Role of Civil/Structural Engineering

Performance-based design: Utilize advances in conventional design to

energize new nuclear construction Bridge the engineering skill gap in structural

and earthquake engineering

New and emerging technologies: Response modification devices New composite structural systems Modular construction and maintenance Modern construction and life cycle

management

Thank you!

Bozidar Stojadinovic, Associate Professor

721 Davis Hall #1710Department of Civil and Env. EngineeringUniversity of California, BerkeleyBerkeley, CA 94720-1710

boza@ce.berkeley.edu http://www.ce.berkeley.edu/~boza