Damage of Reinforced Concrete Walls from Shock and Impact · solver approach in evaluating damage...

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Damage of Reinforced Concrete Walls from Shock and ImpactCoupled Multi-Solver Approach

Damage of Reinforced Concrete Walls from Shock and ImpactCoupled Multi-Solver Approach

X. QuanDevelopment EngineerCentury Dynamics, ANSYS, Inc.


• Introduction• Methods of Space Discretization (MSD)• Coupled Multi-Solver Approach

– Interaction/coupling among MSD• Numerical Simulations

– Truck bomb explodes near a physical barrier– Boeing 747 jet impacts physical barriers

• Conclusions

Overview


Physical Barriers

• Built around nuclear power plants• May consist of multiple barriers• Usually made of steel-reinforced concretes• Must provide adequate structural strength

to prevent failure under terrorist attacks– complete demolition– projectile/fragment penetration– spalling of barrier materials


• Can supply detailed and accurate stress/strain fields than simplified analytical approaches

• Use nonlinear dynamic analysis computer program ANSYS AUTODYN

• Investigate damage initiation and development in a steel reinforced concrete wall under shock and impact loadings

Numerical Simulations


Space Discretization

• Lagrange– numerical grid moves with material

• Euler– material moves through fixed numerical grids

• ALE (Arbitrary Lagrange Euler)– rezoning the interior continuously

• Meshfree: Smooth Particles Hydrodynamics– each particle is an interacting mass and

interpolation point


Space Discretization

• Use Single Space Discretization Method– Advantage

• easy setup of computational models– Disadvantages

• not appropriate to all the regimes of the problem• response of structures to an explosion: detonation

and blast are best modeled by Euler while structural response is best modeled by Lagrange

• Need Coupled Space Discretization Methods-Coupled Multi-Solver Approach


Coupled Multi-Solver

• Lagrange/Lagrange– interactions between Lagrangian grids– contact/slide surfaces– best to simulate impact problems

• Euler/Lagrange– coupling between Eulerian/Lagrangian grids– best to simulate structural response to

explosive loadings


Concrete Wall


Concrete Wall


Material Modeling

• Concrete: RHT Strength and Failure– pressure hardening– strain hardening– strain rate hardening– damage (strain softening)

• Reinforced Steel Bars– von Mises strength– ultimate strain failure– reinforced ratio: 0.8%


Numerical Modeling

• Concrete is represented by– 36,000 Lagrange solid elements

• Steel rebars are represented by– 6,000 beam elements

• Explosive detonation and expansion of gas products are modeled by Euler solvers– from 1,000,000 to 2,000,000 Euler-Ideal gas

elements in 3D simulations• Euler/Lagrange coupling is applied


Location of Bomb


1D to 3D Remap

• 1D Euler simulation on explosive detonation and its spherical expansion

• Before it reaches the wall, 1D blast field is remapped onto a 3D Euler-Ideal gas grid

• Advantages of remapping– unique feature of ANSYS AUTODYN– save a lot of computing time in 3D calculation– accurate modeling early stages of the blast


1D to 3D Remap


Damage: Contact

Front View

Back View


Damage: Contact


Damage: 5m

Front View

Back View


Damage: 10m/20m

10m, front 20m, front


Total Energy

5 m Detonation

20 m Detonation

10 m Detonation

Tota

l Ene

rgy

(µJ)

Time (ms)


Summary

• 60m wide, 30m high, and 1m thick steel-reinforced concrete wall is considered

• Truck bomb contains 5000Kg TNT• The wall stands when the bomb explodes at

– 10m– 20m

• The wall fails when the bomb explodes at– 0m, contact detonation– 5m


Jet Impact


Material Modeling

• Airplane is made of aluminum with– linear equation of state– piecewise linear strain hardening strength– ultimate strain failure– erosion

• Thickness is adjusted so the overall weight of the entire airplane and weight distribution among fuselage, engines, and fuel are correctly represented.


Numerical Modeling

• Concrete is represented by– 56,000 solid elements for 1m thick wall– 186,000 solid elements for 3m thick wall

• Steel rebars are represented by– 16,000 beam elements

• Airplane is represented by– 15,000 shell elements

• Lagrange/Lagrange interaction is applied


1m Thick Wall


3m Thick Wall


Damage: 1m Thick

Front View

Back View


Damage: 3m Thick

Front View

Back View


Summary

• 1m & 3m thick, 150m wide, 60m high steel-reinforced concrete walls are considered

• Walls are impacted by a Boeing 747 passenger jet

• Impact velocity: 83.3m/s (300km/s)• 1m thick wall fails under the impact• 3m thick wall withstands the impact


Conclusions

• The shock and impact simulations demonstrate the successful use of the coupled multi-solver approach.

• ANSYS AUTODYN has the capability to simulate various terrorist threats against physical barriers of nuclear power plants.

• ANSYS AUTODYN can be the most cost effective numerical tool for physical barrier designers


References

• X. Quan, et al, Applications of a coupled multi-solver approach in evaluating damage of reinforced concrete walls from shock and impact, 18th international conference on structural mechanics in reactor technology , Beijing, China, August 7-12, 2005

• M. Katayama et al, Numerical simulation of jumbo jet impacting on thick - concrete wall—effects of reinforcement and wall thickness, 2nd Asian conference on high pressure research, Nara, Japan, November 1-5, 2004

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