Comparison of VCE Prediction Methods in Terms of Vulnerability of Structural Damage TNO Multi-Energy & Baker-Strehlow-Tang ASCE SEI Structures Congress - March 30, 2012
Trey Turner Atkins - Oil & Gas
Overview • Background • VCE Prediction Methods • Initial Comparison • Comparison via Structural Response • Results
Vapor Cloud Explosions Prediction Methods • Simplified (empirical) • Baker-Strehlow-Tang (BST) • TNO multi-energy (ME) • Phenomenological • Based on both theoretical and empirical methods • Computational fluid dynamics (CFD) • The most accurate method for determining blast pressures. • The skill & resources required to undertake CFD studies makes it prohibitive for many situations
Comparison Exercise : ME & BST Methods • Two explosion scenarios are considered for a petrochemical facility 1. Scenario 1: - Ethylene / High Congestion (Detonation like VCE) 2. Scenario 2: Propane / Med. Congestion (Deflagration VCE)
Initial Comparison: Scenario 1 Overpressure
Impulse
Scenario 1 - Ethylene Release
Scenario 1 - Ethylene Release
80
1200 TNO MEM
TNO MEM
BST Model
1000
BST Model
60 Impulse (psi-ms)
Free-Field Pressure (psi)
70
50 40 30
800 600 400
20 200
10
0
0 0
100
200
300
400
Distance from Congested Area Edge, R' (ft)
500
0
100
200
300
400
Distance from Congested Area Edge, R' (ft)
500
Initial Comparison: Scenario 2 Overpressure
Impulse
Scenario 2 - Propane Release
Scenario 2 - Propane Release
10
300 TNO MEM
BST Model
8
250 Impulse (psi-ms)
Free-Field Pressure (psi)
TNO MEM
6
4
BST Model
200 150 100
2 50
0
0
0
100
200
300
400
Distance from Congested Area Edge, R' (ft)
500
0
100
200
300
400
Distance from Congested Area Edge, R' (ft)
500
Response Assessment : Focus Typical Process Work Building (PWB) for Offshore Facility, similar to Portable Building in Petrochemical Facilities • Stainless & Carbon Steel Framing • Thin Gage Corrugated Panels • HVAC Components • Door Framing
24 ft
9 ft
13 ft
BLAST DIR.
Structural Damage & Vulnerability: Approach Probabilistic • Probit Method (probability unit)
-15.6
Death from lung Hemorrhage -77.1
Structural damage -23.8
1.93
6.91
2.92
Probit Parameters
Eardrum rupture
k1 k2
1. Probit Parameters 2. Compute Vulnerability or Structural Damage (Generalized Level) 0.18
1. Select Component 2. Idealization / Transformation/Perf. Criteria 3. Component Damage (Component Level)
• MDOF/NLFEA 1. Model /Analyze 2. Damage (Detailed Level)
0.16 0.14 0.12
Deflection (m)
Deterministic • Elasto-plastic SDOF Method
0.1 0.08 0.06 0.04 Dynamic
0.02
Static (and elastic)
0 0
30
59
89
119
148Time (ms) 178
208
238 1.59 267 Ductility 297 = 1.59 327 DAF=
Scenario 1 Results: Probit & SDOF Probit
SDOF Scenario 1: Ethylene Release
Scenario 1 - Ethylene Release
TNO MEM BST Model
100 80 70
Ductility , μ
Structural Damage (%)
90
60 50 40 30 20 10 0 16
33
66
98
131
197
328
Distance from Congested Area Edge (ft)
492
20 18 16 14 12 10 8 6 4 2 0
TNO ME BST
33
131
197
328
492
Stand Off , R' (ft) The ductility levels only given up to a value of 20
Scenario 2 Results: Probit & SDOF Probit
SDOF Scenario 2 - Propane Release
Scenario 2: Propane Release
TNO MEM BST Model
100
80 70 Ductility , μ
Structural Damage (%)
90
60 50 40 30 20 10 0 16
33
66
98
131
197
Distance from Congested Area Edge (ft)
328
492
20 18 16 14 12 10 8 6 4 2 0
TNO ME BST
33
131
197
328
492
Stand Off , R' (ft) The ductility levels only given up to a value of 20
NLFEA/MDOF Results: Scenario 2 TNO ME
BST
Impulse (psi-ms)
350 300
TNO ME (Impulse)
131ft Stand-off
250
BST (Impulse)
200 150 100 50 0 0
50
100
150
200
250
300
Distance From Congested Area (ft)
350
400
450
500
NLFEA/MDOF Results: Scenario 2 TNO ME
BST
Impulse (psi-ms)
350 300
TNO ME (Impulse)
328ft Stand-off
250
BST (Impulse)
200 150 100 50 0 0
50
100
150
200
250
300
Distance From Congested Area (ft)
350
400
450
500
Observations For Scenario 1 (Ethylene VCE)
•
•
The TNO ME method predicts higher overpressure and impulse inside 100 ft. Outside 100 ft the results begin to agree Structural damage due to TNO ME and BST predicted loads tend to become comparable at distances less than 200 ft In the far field the damage caused by BST predicted loading tends to be higher than that predicted by the TNO ME method
Scenario 1 - Ethylene Release
80 TNO MEM
70
Free-Field Pressure (psi)
•
BST Model
60 50 40 30 20 10 0 0
100
200
300
400
500
Distance from Congested Area Edge, R' (ft)
Scenario 1: Ethylene Release
•
•
TNO ME method predicts significantly higher overpressures than BST model at low distances (i.e., < 300 ft). In the far-field the two methods produce similar pressures. Impulse predictions with BST are lower than TNO ME model at lower distances. They are higher at further distances
Ductility , μ
Scenario 2 (Propane VCE)
20 18 16 14 12 10 8 6 4 2 0
TNO ME BST
33
131
197 Stand Off , R' (ft)
328
492
Observations Scenario 2 cont…
•
20 18 16 14 12 10 8 6 4 2 0
TNO ME BST
33
131
197
328
492
Stand Off , R' (ft) 16
Lat. Deflection (in)
•
Results indicate the TNO ME method predicts loading that results in higher levels of structural damage than that based on the BST method TNO ME method predicts loading that results in higher levels of structural damage than that based on the BST method. This is particularly evident at a range of approximately 200ft where the structural damage from TNO ME loading is significantly (~40%) higher than that computed from the BST method. At distances greater than 200 ft the damage is comparable with both methods For several test cases, NLFEA was undertaken and the results indicate structural damage will be comparable with considering the above conclusions and scenarios in the present study
Ductility , μ
•
Scenario 2: Propane Release
14 12 10
8 6 4
S2-BST-132
2
S2-TNO-132
0 0
25
50
75
Time (ms)
100
125
150
The End Contact Information Trey N. Turner Senior Consultant, Global Technical Expert – Analysis in Design (Fire, Explosion, and Impact) Office: 713-576-8555 | Mobile: 713 410-2270 | Email:
[email protected]
Atkins Energy, Oil & Gas Division
17220 Katy Freeway, Suite 200 Houston, Texas 77094 Office: 713-576-8500 | Fax: 713-576-8501 | Web: www.atkinsglobal.com
