Numerical investigation of internal explosions in steel pipes P. - - PowerPoint PPT Presentation

Numerical investigation of internal explosions in steel pipes

• P. Bonalumi, M. Colombo, M. di Prisco

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• P. Bonalumi, M. Colombo, M. di Prisco
• Project:

ACCIDENT - Advanced Cementitious Composites In DEsign and coNstruction

• f safe Tunnel
• Cooperation between Italy and Switzerland funded by INTERREG programme

and supported by the European Community and the Switzerland Confederation

• Aim:

Design of a precast tunnel lining, to be built by means of TBM technology, considering exceptional loads.

General Framework

FORMULATION OF THE PROBLEM

Material: Mechanical characterization at high temperature and high strain rate Meso-structure: Study of soil-structure interaction under shocks waves (shock tube) Structure: Fire and blast tests within concrete pipes embedded in soil

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• P. Bonalumi, M. Colombo, M. di Prisco

FORMULATION OF THE PROBLEM

Definition of the problem

5 Reflected pressure transducers 1 Incident pressure transducer

Open-ended steel pipe subjected to a single centred internal detonation

• 10 mm thick
• 1 m long
• 0.61 m outer diameter

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• P. Bonalumi, M. Colombo, M. di Prisco

FORMULATION OF THE PROBLEM

Definition of the problem

• Nature of explosive
• Quantity of the explosive
• Shape of the charge
• Explosion kind
• Explosion position

High Energy Solid Explosive 3, 6, 12, 24 grams charges Cylindrical charge Single point explosion Centre of the pipe middle section

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• P. Bonalumi, M. Colombo, M. di Prisco

NUMERICAL MODELLING

Framework of the problem

NUMERICAL CODE: EUROPLEXUS

• CFD explicit finite element code for transient dynamic problems
• Developed by the European Joint Research Centre (JRC) of Ispra and

Commissariat à l’Energie Atomique (CEA) of Saclay MODELS: Axisymmetric 2D and 3D simulations of 3-grams explosive tests OBJECTIVE: Assessment of the prediction capabilities of the numerical model

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• P. Bonalumi, M. Colombo, M. di Prisco

NUMERICAL MODELLING

Models

2D 3D_A 3D_B 3D_C

40x40x80mm 40x40x80mm 40x40x40mm 40 x 40 mm Bubble Size 20x20x25mm 20x20x25mm 2 x 2 x 3 mm 10 x 10 mm Smallest size 30 x 25 mm 30 x 25 mm 20 x 20 mm 10 mm Smallest size N. Type N. Type 1280 1280 576 48 4-nodes shell 4-nodes shell 4-nodes shell 2-nodes shell Structure Fluid 61440 61440 107328 5760 8-nodes hexahedron 8-nodes hexahedron 8-nodes hexahedron 4-nodes quadrilateral Elements 1.2 x 1.2 x 1m 1.2 x 1.2 x 1m 0.6 x 0.6 x 1m 0.6 x 1 m Mesh Size 3D_C 3D_B 3D_A 2D

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• P. Bonalumi, M. Colombo, M. di Prisco

NUMERICAL MODELLING

Description

FLUID-STRUCTURE INTERACTION: Arbitrary Lagrangian Eulerian

• Permanent
• Conforming

FLUID: Eulerian description STRUCTURE: Lagrangian description

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• P. Bonalumi, M. Colombo, M. di Prisco

NUMERICAL MODELLING

Materials

STEEL Linear-elastic

STRUCTURE:

{ {

7800 kg/m3 ρ Density 0.3 ν Poisson’s ratio 210000 N/mm2 E Young’s modulus 2.0833 x105 Nm/kg eint Internal energy 1.2 kg/m3 ρ Density 1.4 γ Specific heat ratio 101325 Pa p Pressure

FLUID:

Inviscid and Compressible Perfect gas

p=(1)eint

EXPLOSIVE:

Note Vbub , Wtnt :

• Detonation energy:
• WTNT Overpressure :
• Bubble Overpressure:
• Bubble of high compressed air
• Larger than the real solid explosive
• Bubble overpressure:

pbub= f(Vbub,W)

eTNT =W 4520 kJ/kg pTNT = eTNT Vbub (1) bub=0.2205log(pTNT)+2.265 pbub= pTNT bub + p0 fbub= pbub p0 eint,bub=eint fbub

AIR OVERPRESSURE BUBBLE

Baloon model

[Brode1955, Larcher2010]

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• P. Bonalumi, M. Colombo, M. di Prisco

A B

A B

3D_A

A B A B

NUMERICAL MODELLING

Results - Pressure

2D 3D_A POINT A POINT B POINT A 3D_B - 3D_C POINT B

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• P. Bonalumi, M. Colombo, M. di Prisco

A B A B

NUMERICAL MODELLING

Results - Radial Displacements

2D 3D_A POINT A ZOOM _ POINT A POINT B ZOOM _ POINT B

CPU = 6 min CPU = 160 min

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• P. Bonalumi, M. Colombo, M. di Prisco

A B 3D_B - 3D_C

A B

NUMERICAL MODELLING

Results - Radial Displacements

3D_A POINT A ZOOM _ POINT A POINT B ZOOM _ POINT B

CPU = 160 min CPU_B = 81 min CPU_C = 441 min

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• P. Bonalumi, M. Colombo, M. di Prisco

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EXPERIM.

Pressure history along Pressure history along the tube he tube axis axis

[mm]

D E F

p1,p2,p3,p4,p5 - pINC Pressure transducers

LONGITUDINAL SECTION TRANSVERSAL SECTION

pINC

pINC pINC p1 p1 p1 p1

B

First Peak of First Peak of Reflected Pressure History eflected Pressure History at the tube at the tube internal surface nternal surface

NUMERICAL RESULTS

PRESSURE HISTORY Comparison numerical - experimental results (explosion section and end section) for 3g charge

NUMERICAL MODELLING

3D_C

Average Average curve on 12 urve on 12 nominal identical tests

• minal identical tests

Representative Representative curve on 12 curve on 12 nominal identical tests

• minal identical tests

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• P. Bonalumi, M. Colombo, M. di Prisco

First Peak of First Peak of Reflected Pressure History eflected Pressure History at the tube at the tube internal surface nternal surface

1 4 5

[mm]

D E F

p1,p2,p3,p4,p5 - pINC Pressure transducers

LONGITUDINAL SECTION TRANSVERSAL SECTION

pINC

B

NUMERICAL RESULTS PRESSURE HISTORY

Comparison numerical-experimental results along the tube longitudinal axis for 3g charge

NUMERICAL MODELLING

Representative Representative curve on 12 curve on 12 nominal identical tests

• minal identical tests

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• P. Bonalumi, M. Colombo, M. di Prisco

NUMERICAL MODELLING

Conclusions

Regarding pressure-time history:

• In this case, 2D model shows a quite good agreement with 3D model

2D model is satisfactory in predicting blast loads on structure

• Boundary conditions have negligible influence on pressure-time history
• Small differences of bubble size and shape have negligible influence on the pressure-

time function (just small

Regarding radial displacement-time history:

• 2D model shows a good agreement with 3D model (especially for the first milliseconds)
• Boundary conditions influence the response of the pipe central section

Regarding experimental pressure-time history:

• 3D model satisfactorily predicts the peak pressures and the pressure-time function, but
• verestimates the wave propagation along the pipe.

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• P. Bonalumi, M. Colombo, M. di Prisco

…Thank you for your attention!!!

Numerical investigation of internal explosions in steel pipes