CURRENT RESEARCH AND INDUSTRIAL APPLICATIONS OF INTEGRATED SRA AND QRA MODELS Philip Smedley.
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Transcript of CURRENT RESEARCH AND INDUSTRIAL APPLICATIONS OF INTEGRATED SRA AND QRA MODELS Philip Smedley.
CURRENT RESEARCHAND
INDUSTRIAL APPLICATIONSOF
INTEGRATED SRA AND QRA MODELS
Philip Smedley
ASA SRA QRA
HFA
Thematic Network on Safety and Reliability of Industrial Products, Systems and Structures
http://mar.ist.utl.pt/saferelnet
OBJECTIVETo provide:
consistent, safe & cost-effective solutions
for a range of industrial systems
across different industrial sectors
throughout the system’s life-cycle.
Steering
Committee
Thematic Network Management Dissemination & Exploitation (WP1)
Coordinator: IST
EU Commission
WP5 WP leader RCP
WP4 WP leader ETHZ
WP6 WP leader BUW
WP7 WP leader IST
WP8 WP leader PAFA
WP3 WP leader DAP
WP9 WP leader NTNU
WP2 WP leader EQE
WP10 WP leader WSA
WP2 Participants
WP3 Participants
WP4 Participants
WP5 Participants
WP6 Participants
WP7 Participants
WP8 Participants
WP9 Participants
WP10 Participants
Industrial Committee
Liaison Committee
SteeringCommittee
LiaisonCommittee
PROGRAMME
PROGRAMME
WP SCOPE LEADER
1 Management, Dissemination & Exploitation IST
2 Risk Assessment Methodology EQE
3 Human & Org. Factors in Risk Assessments DAP
4 Integration of Risk & Reliability Formulations ETHZ
5 Reliability Based Design RCP
6 Assessment of Existing Structures & Life Extension BUW
7 Risk & Cost Based Inspection & Maintenance Planning IST
8 Standardisation and Codes PAFA
9 Training and Education NTNU
10 Strategy in the Various Industrial Sectors Atkins
EQE InternationalPAFA Consulting Engineers
Atkins BOMEL Limited
Petrellus LimitedCorrOcean Ltd
Liverpool John Moores UniversityUniversity of Liverpool
The University of SurreyNetwork Rail
Highways AgencyHealth and Safety Executive
UK PARTNERS
ASA SRA QRA
HFA
INTEGRATION
ADVANCED STRUCTURAL ANALYSIS
STRENGTHS• Solutions to complex / time-dependent problems• Speed – cost-effective solutions• System’s redundancy and reserve strength• Uncertainty analysis – parametric variations
WEAKNESSES• Difficult to estimate accuracy in results• Potential errors or inadequacies in programs• Potentially inadequate user skill levels
STRUCTURAL RELIABILITY ANALYSIS
STRENGTHS• ‘Complete’ representation of loading and
resistance uncertainties in design problems• Fully quantified reliability estimates • Updated estimates as new data added or
improved by expert opinion (Bayesian updating)
WEAKNESSES• Better for empiric rather than parametric formulae• If human factors are included they are generally
fairly crude or simplistic estimates.
QUANTIFIED RISK ASSESSMENT
STRENGTHS• Causes and consequences of hazard modelled• Strong for operational and accident problems• Quantification of underlying issues - based on
incident data and expert opinion (frequentist)
WEAKNESSES• Lack of data or understanding of problem or
inaccurate data due to biased opinions• Uncertainty only considered in the underlying
statistics rather than the model• Not good for time-dependent problems
HUMAN FACTOR ASSESSMENT
STRENGTHS• Most (80%) incidents caused by human error
therefore essential element in our understanding• Human behaviour often very predictable• Includes individual and corporate behaviour
WEAKNESSES• Cynicism - knowledge of HFs generally from
specialists outside the engineering industry• High uncertainties in models and data (for now)• Difficult issues of cultural/society differences
SRA-QRA-HFA INTEGRATION
IS IT FEASIBLE?
A Qualified - Yes.
A number of common issues:• Mathematical models are of a similar format• All seek to achieve a target level of safety
(Annual target reliability or risk acceptance criteria)• Need quality, unbiased data (historic or opinion)
SRA-QRA-HFA INTEGRATION
INITIAL INTEGRATED MODELS
1. Reliability distribution replaces deterministic quantification in risk analysis - fault tree
2. Human factor Bayesian Probabilistic Networks can readily be reformulated into fault trees
INTEGRATION – Example 1
INST. FOR ELECTRIC POWER RES. (HUNGARY)
1. Process Analysis – Deterministic Assessment1. Initiating event identification
2. Event tree development
2. System Analysis – Reliability Assessment1. Fault tree development
2. Hardware failure data estimation
3. Human failure data estimation
3. Structural Analysis – Fragility Assessment
INTEGRATION – Example 1
SWALE CROSSING : Kent – Isle of Sheppey
INTEGRATION – Example 2
INTEGRATION – Example 2
PAFA CONSULTING ENGINEERS
1. Risk Analysis – AASHOTO Guidelines1. Number of Ships subdivided into 6 classes
2. Probability of aberrance (human error, mechanical failure, severe environmental loading)
3. Probability of collision with bridge pier
4. Probability of exceeding bridge pier strength
2. To Probability of Aberrance add:1. Mechanical reliability of bridge lift mechanism
2. Avoidance of other vessels in area (esp. yachts)
PROBLEM: ACCEPTANCE CRITERIA
Objective Hazard Potential
Objectively known
Subjectively realised
Taken into account
Accep
ted R
isk
No
tad
equ
ate
Neg
lected
No
t Realised
No
t kno
wn
Risks modelled
Adequately quantified (good data)
Correct model
Wro
ng
AcceptedRisk
Accurate Risk Assessment
Inaccuracies due to Human Errors
from Faber/Schneider
IS IT DESIRABLE?
Sometimes• Expanding a reliability model, for example, to
account for poorly defined human factors will add time and cost but not improve the overall understanding of the system.
• The three approaches have been developed to solve specific problems. Each approach has many models each with specific strengths and weaknesses. One integrated approach is likely to be less rigorous in some instances.
SRA-QRA-HFA INTEGRATION
SAFERELNET APPROACH• Seeking to develop a consistent mathematical
model that may be used to integrate some of the strengths of SRA – QRA – HRA.
• If such an integrated approach can be developed, to consider the strengths and weaknesses within such a model.
• Discuss and develop thinking for a consistent risk and reliability acceptance criteria.
SRA-QRA-HFA INTEGRATION
http://mar.ist.utl.pt/saferelnet