Poznan University of Technology

WORKSHOP 2010 ON CONSTITUTIVE MODELING IN APPLICATIONS FOR INDUSTRIAL PROCESSES KRAKÓW, 1-3 September, 2010

Poznan University of Technology

ASSESSMENT OF PUBLIC SAFETY AFTER GAS EXPLOSION

INSIDE A CIVIL ENGINEERING STRUCTURE

Tomasz Łodygowski and Piotr W. Sielicki

Institute of Structural Engineering (ISE)Poznań University of Technology

ul. Piotrowo 5, 60-965 Poznań, Polande-mail: [email protected],

[email protected]



PRESENTATION OUTLINE:

- MOTIVATION

- INTRODUCTORY REMARKS

- NUMERICAL MODEL AND COMPUTATIONS

- PUBLIC SAFETY

- CONCLUSIONS



MOTIVATION

PUBLIC SAFETY ASSESSMENT (during building employment for retrofitting)

- SAFE

- WOUNDED

- BADLY WOUNDED

FLOOR PLANNING (before built during a design process for changing floor configuration)


INTRODUCTORY REMARKS

- Full spatial modeling covers 30 by 60 m2 area and 3.5m high- Underground concrete office rooms with plant room in „p1”- There is an open space without blast doors, and door heads are not included- Rigid walls represent the most risk scenario, where the reflection is the highest


Door heads are not included


NUMERICAL MODEL

- The analyzed scenario is: Escaping of propane from a broken installation in the plant room

- Assumption: 50% propane-air concentration in the plant room before an explosion- The important property of propane-air mixture; an Initial Specific Energy value bases on Alternate Energy Systems, Inc. online data- Propane behavior is simulated by JWL equation of the state

- Air behavior is simulated by IDEAL GAS equation of the stateWORKSHOP 2010 ON CONSTITUTIVE MODELING IN APPLICATIONS FOR INDUSTRIAL PROCESSES KRAKÓW, 1-3

September, 2010

Type of ChargePropane-Air Mixture

Mass [kg] 330

Volume [m3] 172.8

Specific Energy [J/kg] 2.73e7

Density [kg/m3]626 liquid 1.9 mixture

Detonation speed [m/s] 1680

ZA TTRpp

00

20

202

01

01

exp1exp1 mERR

BRR

Ap


NUMERICAL MODEL

Coupled Eulerian-Lagrangian is used to simulate a pressure evolution in the air space inside the office area

Source code: Abaqus 6.9 Explicit code is used for calculationProblem size: 2.5e6 Finite Elements EC3D8RElement size: 0.125 by 0.125 by 0.125 m3

Analyzed time: 0.2 secComputational time: 3600x15 seconds (average time for one analysis)Boundary conditions: corridors & rooms (wall, floor, ceiling) are fixed with use of zero velocity condition

FE requested results: Over- Pressure values and velocity in time and space functionTransferred requested results: Mean pressure-time dependency and impulse for every room


Klip wideo


NUMERICAL MODEL

Pressure maps in time function allows for assessment of real hazard for every room, only if some criterion is known.


t= 0.001 s t= 0.005 s

t= 0.05 s t= 0.1 s


PUBLIC SAFETY

Human tolerance to the blast output of an explosion is relatively high. However, the orientation of a person (standing, sitting, etc.) is really important. The pressure tolerance for short-duration blast loads is significantly higher than that for long-duration blast loads. There are used two separate criteria, in agreement US standard i.e. Unified Facilities Criteria (UFC) UFC 3-340-02, for assessment public safety.

1. LUNG DAMAGE 2. EARDRUMS RUPTURE



PUBLIC SAFETY

The mean properties are obtained for each office room and could be further compared with safety criteria.

The results for one room (Plant Room) are presented below


Pressure – Time relation in the P1 room

Peak overpressure0.62e9[ Pa ]Duration time 0.02 [ s ]Specific Impulse* 3.1e6[ Pa s / W* ]

Pressure contour lines 0.001s after detonation


PUBLIC SAFETY

The mean values are obtained for each room and compared with both criteria.


Safe zone (below criteria)

Wounded zone (50%)

Badly wounded zone

Safety zones base on EARDRUMS RUPTURE vs. LUNG DAMAGE criteria

Movie represents EARDRUMS RUPTURE vs. LUNG DAMAGE for badly wounded zone

Klip wideo Klip wideo


PUBLIC SAFETY - RETROFITTING

The structure model is upgraded by rigid door heads to increase public safety in the rooms. The results are presented below for two variants: 0.5 and 1m head high. The results are presented with use EARDRUMS RUPTURE criteria.


0.5m head vs. 1m head for EARDRUMS RUPTURE criterion

Movie represents EARDRUMS RUPTURE for 0.5m vs 1m high doors head and badly wounded zoneKlip wideo Klip wideo


PUBLIC SAFETY

Because of using the rigid door heads there is a significant improvement of safety in the building


Safety zones for basis and upgraded (1m door head) schemes of the floor under EARDRUMS RUPTURE criterion

Safety zones for basis and upgraded (1m door head) schemes of the floor under LUNG DAMAGE criterion

The safety area (green)increases 3 times afterretrofitting process

The safety area (green)increases 5 times afterretrofitting process


CONCLUSIONS

Designer increases a value (square meters) of safety zone area in the structure after use of rigid 1m height door heading

Obtained pressure values are comparable with real overpressure (in agreement with UFC)

Approach may be useful for predicting blast resistant for new-designed or existing structures in relatively short time

Mesh size sensitivity must be checked for analyzing of considerably complex structure including HVAC and elevator duct in the multi levels building


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