Metodologie di valutazione del rischio sismico per grandi impianti industriali

Transcription

1 Metodologie di valutazione del rischio sismico per grandi impianti industriali Marcello Forte AXA Matrix Risk Consultants Davide Spanò AXA Matrix Risk Consultants

2 Earthquakes are uncertain in size and time of occurrence, but not randomly located around the globe. In the picture the size of circles is proportional earthquake energy (i.e., magnitude). Milano, 7/11/2012 2

3 Losses are not following the same distribution of earthquakes U.S. : High-intensity earthquakes, low vulnerability of buildings, high value of goods = low casualties, large business loss. Southern Europe: Moderate intensity earthquakes, high vulnerability of buildings, high value of goods = large casualties, large business loss. Middle east: Moderate intensity earthquakes, high vulnerability of buildings, low value of goods = large casualties, low business loss. In the picture the size of circles is proportional to loss amount. Loss depends on earhtuquake intensity, damage susceptibility of built enviroment in the region affected, and value of goods and activities hosted by the damaged built enviroment. Milano, 7/11/2012 3

4 Nat-Cat loss trend Milano, 7/11/2012 4

5 Seismic Risk qualitative approach Seismic Risk Qualitative Approach Series of descriptions of the effects of the ground shaking on the basis of observed past earthquake in limited area Quantitative Approach This approach has very important positive factors such as: Insurance analysis process: - Risk identification by means of macro-seismic maps (e.g. Munich Re) - Loss Estimation based on damage factors and intensity levels - Loss Estimation refined including corrector coefficients for taking into account both soil and structure characteristics Based on real observation Available world wide It can provide average loss estimation in an area Easy to understand and communicate. Limitations Not really useful for Risk Managers who want to assess the risk of a specific industrial site. Milano, 7/11/2012 5

6 Seismic Risk General approaches Seismic Risk Qualitative Approach Quantitative Approach Risk factors are individually assessed according to the quantitative definition: Milano, 7/11/2012 6

7 Seismic Risk Nominal deficit (NODE) Seismic Risk Qualitative Approach Quantitative Approach NOminal DEficit based Based on the nominal deficit between the structural performance required by the seismic code at the time of construction (nominal capacity) and the structural performance required by the current seismic code (nominal demand). Fragility based Nominal Deficit Seismic Risk Index = N a (Demand Capacity) Seismic Demand imposed by the seismic code currently enforced (required structural performance) Seismic Demand imposed by the seismic code at the time of construction (required structural performance) Milano, 7/11/2012 7

8 Italian seismic code development Milano, 7/11/2012 8

9 Italian seismic code development Milano, 7/11/2012 9

10 Italian seismic code development Milano, 7/11/

11 Nominal deficit evaluation based on basic structural elements Including the structure behaviour Current elastic performance demand Current inelastic performance demand Spectral Nominal Deficit Inelastic performance demand at the time of construction S d (T) current S d (T) design Milano, 7/11/

12 Software package NODE for industrial building assessment 6. Hazard at the time of construction 2. Facility location, 1. age of construction 7. Hazard according to the current seismic code 3. Structural dynamic characteristics 4. Site soil characteristics 8. Current performance demand 9. Performance demand at the time of construction 10. Risk Index = Nominal deficit = current code-based seismic demand compared to that at the time of construction Milano, 7/11/ wind design at the time of construction

13 Case study application industrial buildings risk assessment Name Lat [ ] Lon [ ] Year PGA (475y) Sulmona Uff Sulmona Off Paliano Tito Scalo Off Tito Scalo Uff Tolmezzo Melfi Melfi Uff Melfi Off Cassino Off Cassino Off Cassino Off Bologna Off Bologna ESP Bologna Off Bologna Off Crevalcore Caivano Caivano Atessa Rivalta Off Rivalta Uff Volvera MagazzC Volvera OffD Bari Torino Off Venaria 1/ Venaria 2/ Venaria Venaria 3/ Venaria San Benigno OffA San Benigno OffB Corbetta The Italian INGV map is able to provide, introducing the coordinates, the PGA at 475 yrs PCM April 2006 The Italian territory has been divided in four categories based on the seismic hazard in terms of Peak Ground Acceleration with 10% probability of exceedance in 50 years. Zone 1: high, PGA > 0,25 g Zone 2: Medium, PGA between 0,15 and 0,25 g Zone 3: Low, PGA between 0,05 e 0,15 g Zone 4: Very Low, PGA < 0,05 g Milano, 7/11/

14 INELASTIC NOMINAL DEFICIT PGA 475 for stiff soil Sulmona Off Sulmona Uff Paliano Tito Scalo Off Tito Scalo Uff Tolmezzo Melfi Off Melfi Uff Melfi Cassino Off12 Cassino Off13 Cassino Off166 Bologna Off1-34 Bologna Off1-71 Bologna Off2 Bologna ESP Crevalcore Caivano Caivano Atessa Rivalta Off Rivalta Uff Volvera OffD Volvera MagazzC Bari Torino Off Venaria 1/3 Venaria 2/3 Venaria Venaria 3/3 Venaria San Benigno OffA San Benigno OffB Corbetta Designed according to 1971 bldg code (seismic) Erected in 2008 Sd(T) deficit (construction year, type of structure) Milano, 7/11/ Case study application industrial buildings risk assessment Bologna Off1-34 Bologna Off1-71 Caivano Bologna Off2 Atessa Tolmezzo Tito Scalo Off Tito Scalo Uff Bologna ESP Bari Sulmona Off Crevalcore Venaria Caivano Melfi Off Melfi Uff Paliano Rivalta Off Volvera OffD Torino Off Rivalta Uff Sulmona Uff Venaria Venaria 1/3 Venaria 2/3 Volvera MagazzC Venaria 3/3 Melfi San Benigno OffA San Benigno OffB Cassino Off12 Corbetta Cassino Off13 Cassino Off166 Soil effect. The only site with a D type soil This type of structure has not been influenced by the code change Sd(T) deficit (construction year, type of structure, soil) Crevalcore Bologna Off1-34 Bologna Off1-71 Bologna Off2 Bologna ESP Caivano Atessa Tolmezzo Tito Scalo Off Tito Scalo Uff Rivalta Off Paliano Rivalta Uff Sulmona Off Sulmona Uff Melfi Off Melfi Uff Melfi Torino Off Volvera OffD Bari Caivano Venaria Venaria Cassino Off12 Venaria 1/3 Venaria 2/3 Venaria 3/3 Volvera MagazzC Cassino Off13 San Benigno OffA San Benigno OffB Corbetta Cassino Off166

15 Basic Assumptions Seismic Risk Nominal deficit Compliance with construction regulations of the age of the building Structural quality of the building not considered PROS: Few data easily retrievable required Quantitative risk measure Hazard and Vulnerability are assessed separately Suitable for portfolio analysis (prioritization) CONS: Based on strong assumptions Suitable for engineered structures Easily applicable for Italy Reliable tool for relative indexes Milano, 7/11/

16 Metodologie di valutazione del rischio sismico per grandi impianti industriali Marcello Forte AXA Matrix Risk Consultants Davide Spanò AXA Matrix Risk Consultants

17 Seismic risk general approaches Seismic risk Qualitative Approach Quantitative Approach Deficit analysis Deficit analysis is based on the nominal deficit evaluation between the structural performance required by the seismic code at the time of construction (nominal capacity) and the structural performance required by the current seismic code (nominal demand). Fragility analysis Fragility analysis is widely used in the seismic risk management for seismic loss estimation and is based on the definition of fragility functions. S d (T) current S d (T) design Milano, 7/11/

18 Seismic risk general approaches What s a fragility function? Probability that a component, element or system reaches or exceeds a predefined damage state at a given ground motion intensity Methodologies: Empirical, based on statistics of observed damage from past earthquake Expert opinion, depend on judgment and information of expert Analytical, derived from computational analyses using finite element methodology Fragility analysis (analytical) 1. Based on specific structure model 2. Based on representative types of structures model Milano, 7/11/

19 Probabilità di superamento in 50 anni Seismic Risk - Fragility analysis INDUSTRIAL BUILDINGS ASSESSMENT: 1 PGA Fragility curve for manufacturing building Accelerazione [m/s^2] T=0.5 T=1 T=3 T=4 Hazard curve for Sulmona (AQ) site (probabilistic distribution of peak acceleration) Fragility curve for utility building STEPS FOR THE ASSESSMENT: 1. Evaluation of Probabilistic Seismic Hazard for the site; 2. Evaluation of seismic fragility for each building; Officina Utilities Fragility curve for tank 3. Combination of fragility and hazard for each single structure and determination of probability of failure; Tank 4. Assessment of the expected loss for single structure in collapse case or other limit states; Uffici Fragility curve for office building 5. Combination of expected loss for the entire facility (BI, relationship between facilities, ) Milano, 7/11/

20 Case study application Fragility analysis for the production building Steel buildings Built in 1979 and 1992 dimensions in plan: m 2 Materials: Fe360 grade steel members Fe430 and Fe510 grade steel plates class 8.8 bolts C20/25 concrete General characteristics: 1) Identification of structures: independent blocks 24 x 12 meters spans construction phases: 1) blocks, tot: m 2 2) enlargements, tot: m 2 2) blocks, tot: m 2 Milano, 7/11/

21 Case study application Fragility analysis for the production building 2) Knowledge of buildings : collection of original drawings and design documentation; Beams: One full structural cross section in the x-direction. Columns: type A ( ) two IPE 360 hot-rolled shapes with stiffening plates (th.10 mm) One-bay structural cross section of trusses in x- and y- directions. type B (1991) two IPE 600 hot-rolled shapes battened by means of pieces of HE A 500 hot-rolled profiles tipo C (1991) HE A 400 hot rolled shape Milano, 7/11/

22 Case study application Fragility analysis for the production building From portion: 3) Modeling of structures: finite element model and analytical models; D model X direction 22 levels (0.1-3 g), 30 record : 660 structural analyses D model Y direction 22 levels (0.1-3 g) 30 record 660 structural analyses From 1991 portion: D model 10 levels (0.1-1 g) 30 record 300 structural analyses D model X direction 22 levels (0.1-3 g) 30 record 660 structural analyses D model Y direction Milano, 7/11/ levels (0.1-3 g) 30 record 660 structural analyses

23 Case study application Fragility analysis for the production building 4) Seismic analyses: incremental dynamic analyses (IDA) Several calculations have to be performed in order to simulate the behaviour of the structure PGA Acceleration applied to the model and selected according to fault and soil characteristics Milano, 7/11/

24 Case study application Fragility analysis for production building 5) Extraction of results from the analyses D model Y direction (no P-delta) D model Y direction (P-delta) D model Y direction D model X direction D model Y direction D model X direction Milano, 7/11/

25 Case study application Fragility analysis for the production building 6) Fragility functions estimation based on the analytical results D models X and Y direction D models X and Y direction Milano, 7/11/

26 Case study application Fragility analysis for specific structure Foundamental steps: 1) Identification of structures : structural typologies; 2) Knowledge of buildings : study of all the as built drawings and available documents; 3) Modeling of structures: finite element model and analytical models; 4) Seismic analysis : Linear and Non-linear analysis; PROS: Very good results taylored for specific structure/facility Can account (in principle) for all type of losses including BI and supply chain interruption; Provide the best tool for decision making; i.e., probability of financial loss 5) Extraction of the results; 6) Fragility functions estimation CONS: Requires detailed (site specific) modeling of seismic hazard; Requires detailed modeling of structural performance for computer simulation; Requires fine loss estimation induced by earthquakes; For all the reasons above it is very costly. Milano, 7/11/

27 Seismic risk general approaches Seismic Risk Qualitative Approach Quantitative Approach Nominal Deficit analysis Fragility analysis 1. based on specific structure models 2. based on representative types of structures models Fragility functions are developed using analytical methods for the assessment of representative types of structures (prototypes). The analytical method accounts also for the variability of the structural characteristics enclosed in the building typology considered. Milano, 7/11/

28 2. Fragility analysis for representative types of structures Steps identified : Identification of the main typologies of buildings according to existing fragility functions Collection of the existing fragility functions studies Creation of a tool able to store and process the fragility functions collected Milano, 7/11/

29 Seismic risk Fragility analysis for representative types of structures Methodology developed: LS1 100% LS2 81% LS1 LS2 LS3 No significant damage to structure; Moderate structural damage which can be repaired economically; Severe structural damage which can not be repaired economically; LS3 6.4% 0.16 g Milano, 7/11/

30 Seismic risk Fragility analysis for representative types of structures AXA Matrix Risk Consultants TOOL The software aims: 1. Catalogue various fragility functions related to different industrial building key-parameters 2. Enable the selection of building keyparameters which automatically are matched with the representative fragility function Milano, 7/11/

31 Seismic risk Fragility analysis for representative types of structures 3. Find the site hazard based on the location. Milano, 7/11/

32 Seismic risk Fragility analysis for representative types of structures 4. Identify the conditional probability of reaches or exceeds each of the three predefined damage states Milano, 7/11/ g

33 Seismic risk Fragility analysis for loss estimations Evaluation of fragility functions are used then to estimate potential damage and losses of future earthquake Milano, 7/11/

34 Probability of Failure Seismic risk From structural to nonstructural damages Milano, 7/11/ IM (Ground Motion Intensity) [g]

35 Axa Matrix Risk Consultants Marcello Forte Regional Engineering Manager marcello.forte@axa-matrixrc.com Davide Spanò Loss Prevention Engineer davide.spano@axa-matrixrc.com Milano, 7/11/