Systematic Risk Assessment of High-risk Structures Against Disproportionate Collapse
Content
Systematic Risk Assessment of Highrisk Structures against Disproportionate Collapse Based on IStructE guidelines
Harikrishnan Panikkaveettil
Key Concepts and Eurocode Requirements
2. BACK GROUND AND DESIGN OBJECTIVES 7/18/2014
Harikrishnan Panikkaveettil
2
Risk-based approach for design (against disproportionate collapse)
• Not a substitute for the lack of structural form • Objectives – Identify Hazards – Eliminate the hazards – Develop risk-reduction measures
• Level of detail – Engineer to decide – Qualitative, Semi-quantitative & fully quantitative
7/18/2014
Harikrishnan Panikkaveettil
3
Risk • Hazard: something which has the potential to cause harm – Action on the structure – “Soft” hazard [eg: failure to communicate effectively]
• Risk = Likelihood × Consequence
7/18/2014
Harikrishnan Panikkaveettil
4
Risk-based design • “Acceptable level of risk” – unique for a structure • Good risk management – Costs of risk reduction ≈ magnitude of risk
• Secondary benefit – Indentifying and communicating risks
7/18/2014
Harikrishnan Panikkaveettil
5
Reduction of risk As low as reasonably practicable
• Approach 1: – Reduce all risk to threshold
• Approach 2: – Reduce all risks so far as reasonably practicable(SFARP)
• Risks above threshold – unacceptable 7/18/2014
Harikrishnan Panikkaveettil
6
Building risk classification • • • •
Class 1 Class 2A – Lower Risk Group Class 2B – Upper Risk Group Class 3 – High Risk Group – “a systematic risk assessment of the building should be undertaken taking into account both foreseeable and unforeseeable hazards”
7/18/2014
Harikrishnan Panikkaveettil
7
Framework for a systematic risk assessment
3. DEVELOPMENT OF A SYSTEMATIC RISK ASSESSMENT 7/18/2014
Harikrishnan Panikkaveettil
8
Framework • Single author – full responsibility – Suitable Qualification and Experience (SQEP) – Risk assessment workshop – HAZard and Operability study (HAZOP)
• Framework – Scenario-independent design – Scenario-dependent design
7/18/2014
Harikrishnan Panikkaveettil
9
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 10 remaining risks
Likelihood scale Example Likelihood scale Likelihood Frequent/ common
Frequency
Approximate return period (based on 50 year design life)
10 times in design life
Less than 1 in 10 years
Likely
50% probability of occurrence during design life
1 in 10 years to 1 in 100 years
Unlikely
10% probability of occurrence during design life
1 in 100 years to 1 in 1000 years
Rare
2% probability of occurrence during design life
1 in 1000 years to 1 in 10000 years
Improbably
0.1% probability of occurrence during design life
1 in 10000 years to 1 in 100000 years
Negligible
Less than 0.1% probability of occurrence during design life
Greater than 1 in 100000 years
7/18/2014
Harikrishnan Panikkaveettil
11
Consequence Scale
7/18/2014
Harikrishnan Panikkaveettil
12
Risk Threshold
7/18/2014
Harikrishnan Panikkaveettil
13
Parties involved in risk assessment • • • • • •
Client/building owner Structural engineer (designer) Other designers External stakeholders Building control authority CDM coordinator/ risk management specialist
7/18/2014
Harikrishnan Panikkaveettil
14
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 15 remaining risks
(1) Identify the hazards
7/18/2014
Harikrishnan Panikkaveettil
16
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 17 remaining risks
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 18 remaining risks
(2) Eliminate the hazards • Easier at the early stages of design
7/18/2014
Harikrishnan Panikkaveettil
19
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 20 remaining risks
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 21 remaining risks
(3) Determine the tolerable risk threshold • Extent of collapse for any given likelihood • The threshold should be skewed towards consequence – This effect diminishes beyond a certain point
7/18/2014
Harikrishnan Panikkaveettil
22
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 23 remaining risks
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 24 remaining risks
(4) Evaluate the risk • Risk = likelihood × consequence • Watch points – Sensitivity of solution/risk
7/18/2014
Harikrishnan Panikkaveettil
25
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 26 remaining risks
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 27 remaining risks
(5) Identify risk reduction measures • Irrespective of level of risk • Reduction of a risk may increase another risk • Not limited technical – “Soft” (procedural)
7/18/2014
Harikrishnan Panikkaveettil
28
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 29 remaining risks
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 30 remaining risks
(6) Cost-benefit assessment • Cost – financial cost, programme delay… • Benefit – reduction in fatality, injury
7/18/2014
Harikrishnan Panikkaveettil
31
Harikrishnan Panikkaveettil
Key Concepts and Eurocode Requirements
2. BACK GROUND AND DESIGN OBJECTIVES 7/18/2014
Harikrishnan Panikkaveettil
2
Risk-based approach for design (against disproportionate collapse)
• Not a substitute for the lack of structural form • Objectives – Identify Hazards – Eliminate the hazards – Develop risk-reduction measures
• Level of detail – Engineer to decide – Qualitative, Semi-quantitative & fully quantitative
7/18/2014
Harikrishnan Panikkaveettil
3
Risk • Hazard: something which has the potential to cause harm – Action on the structure – “Soft” hazard [eg: failure to communicate effectively]
• Risk = Likelihood × Consequence
7/18/2014
Harikrishnan Panikkaveettil
4
Risk-based design • “Acceptable level of risk” – unique for a structure • Good risk management – Costs of risk reduction ≈ magnitude of risk
• Secondary benefit – Indentifying and communicating risks
7/18/2014
Harikrishnan Panikkaveettil
5
Reduction of risk As low as reasonably practicable
• Approach 1: – Reduce all risk to threshold
• Approach 2: – Reduce all risks so far as reasonably practicable(SFARP)
• Risks above threshold – unacceptable 7/18/2014
Harikrishnan Panikkaveettil
6
Building risk classification • • • •
Class 1 Class 2A – Lower Risk Group Class 2B – Upper Risk Group Class 3 – High Risk Group – “a systematic risk assessment of the building should be undertaken taking into account both foreseeable and unforeseeable hazards”
7/18/2014
Harikrishnan Panikkaveettil
7
Framework for a systematic risk assessment
3. DEVELOPMENT OF A SYSTEMATIC RISK ASSESSMENT 7/18/2014
Harikrishnan Panikkaveettil
8
Framework • Single author – full responsibility – Suitable Qualification and Experience (SQEP) – Risk assessment workshop – HAZard and Operability study (HAZOP)
• Framework – Scenario-independent design – Scenario-dependent design
7/18/2014
Harikrishnan Panikkaveettil
9
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 10 remaining risks
Likelihood scale Example Likelihood scale Likelihood Frequent/ common
Frequency
Approximate return period (based on 50 year design life)
10 times in design life
Less than 1 in 10 years
Likely
50% probability of occurrence during design life
1 in 10 years to 1 in 100 years
Unlikely
10% probability of occurrence during design life
1 in 100 years to 1 in 1000 years
Rare
2% probability of occurrence during design life
1 in 1000 years to 1 in 10000 years
Improbably
0.1% probability of occurrence during design life
1 in 10000 years to 1 in 100000 years
Negligible
Less than 0.1% probability of occurrence during design life
Greater than 1 in 100000 years
7/18/2014
Harikrishnan Panikkaveettil
11
Consequence Scale
7/18/2014
Harikrishnan Panikkaveettil
12
Risk Threshold
7/18/2014
Harikrishnan Panikkaveettil
13
Parties involved in risk assessment • • • • • •
Client/building owner Structural engineer (designer) Other designers External stakeholders Building control authority CDM coordinator/ risk management specialist
7/18/2014
Harikrishnan Panikkaveettil
14
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 15 remaining risks
(1) Identify the hazards
7/18/2014
Harikrishnan Panikkaveettil
16
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 17 remaining risks
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 18 remaining risks
(2) Eliminate the hazards • Easier at the early stages of design
7/18/2014
Harikrishnan Panikkaveettil
19
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 20 remaining risks
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 21 remaining risks
(3) Determine the tolerable risk threshold • Extent of collapse for any given likelihood • The threshold should be skewed towards consequence – This effect diminishes beyond a certain point
7/18/2014
Harikrishnan Panikkaveettil
22
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 23 remaining risks
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 24 remaining risks
(4) Evaluate the risk • Risk = likelihood × consequence • Watch points – Sensitivity of solution/risk
7/18/2014
Harikrishnan Panikkaveettil
25
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 26 remaining risks
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 27 remaining risks
(5) Identify risk reduction measures • Irrespective of level of risk • Reduction of a risk may increase another risk • Not limited technical – “Soft” (procedural)
7/18/2014
Harikrishnan Panikkaveettil
28
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 29 remaining risks
1
Review
2
7/18/2014
Identify the hazards Determine the tolerable risk level
Eliminate the hazards if possible
Risk = Likelihood × Consequence
4
Identify risk reduction measures
5
Benefit / Cost assessment
6
Implement risk reduction
7
Residual risk
8
Sensitivity of the risk assessment
9
ReviewHarikrishnan the overall level of risk Panikkaveettil
3
Communicate 30 remaining risks
(6) Cost-benefit assessment • Cost – financial cost, programme delay… • Benefit – reduction in fatality, injury
7/18/2014
Harikrishnan Panikkaveettil
31
