Robustness of concrete plates with protective coating exposed to a blast load

Robustness of concrete plates with protective coating exposed to a blast load

Robustness of StructuresRobustness of Structures

COST Action TU0601COST Action TU0601

22ndnd Working Group and Working Group and 44thth Management Committee MeetingsManagement Committee Meetings

SeptemberSeptember 2929--3030, 2008, , 2008, TimisoaraTimisoara, , RomaniaRomania

Krzysztof Krzysztof CichockiCichockiKoszalin Koszalin UniversityUniversity of Technologyof Technology

Department of Civil and Environmental EngineeringDepartment of Civil and Environmental Engineering

How to reduce the effects of blast loading on existing structures?

- retrofitting and structural modification;

- application of protective covers.

How to reduce the effects of blast loading on existing structures?

- retrofitting and structural modification;

- application of protective covers.

Numerical simulation of full-scale field tests of concrete slabs subjected to blast loads

Schenker et al.(Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel)

International Journal of Impact Engineering 35 (2008) 184–198

980 kg TNT, distance 20 m;

Concrete slabs 3 x 1 x 0.3 m;

Slabs with aluminum foam coating (36 mm + 1.5) mmand without coating

Slabs after explosion

- without coating

- with coatingFEM model (Abaqus/Explicit):

Reinforced concrete;

Implemented material model for concrete

MATERIAL MODEL FOR CONCRETE MATERIAL MODEL FOR CONCRETE –– BASIC FEATURESBASIC FEATURES

•Different compressive and tensile characteristics;•Initial linear-elastic behaviour;•Hardening/softening in compression;•Softening in tension;•Damage;•Rate-dependent behaviour;

Tension CompressionM.Basista, W.K.M.Basista, W.K.Nowacki Nowacki ((EdsEds), ), Modeling of Damage and Fracture Processes in Engineering MateriaModeling of Damage and Fracture Processes in Engineering Materialsls, , IPPT, 1998IPPT, 1998

RATE-DEPENDENT PLASTIC-DAMAGE MATERIAL MODEL FOR CONCRETE

�� Continuum Continuum Damage MechanicsDamage MechanicsKachanov Kachanov (1958)(1958)

�� Helmholtz free energy potential Helmholtz free energy potential Lubliner Lubliner (1972), (1972), Mazars and PijaudierMazars and Pijaudier--Cabot Cabot (1989)(1989)

�� Two Two independent independent internal scalar damage variablesinternal scalar damage variables ::((tensiontension , , compressioncompression ))LemaitreLemaitre (1984)(1984)

�� Effective stressEffective stress conceptconceptLemaitre and Chaboche Lemaitre and Chaboche (1978)(1978)

�� Rate Rate dependent dependent behaviorbehaviorSimo and Ju Simo and Ju (1987)(1987)

−−−−++++ dd ,

Kachanov, L.M. (1986), Introduction to Continuum Damage Mechanics,Martinus Nijhoff PublishersLubliner, J. (1972), On the Thermodynamical Foundations of Non-Linear Solid Mechanics, Int. J. Non-Linear Mech., Vol. 7Mazars, J.; Pijaudier-Cabot, G. (1989), Continuum Damage Theory. Application to Concrete, J. of Eng. Mech., ASCE, Vol. 115Lemaitre, J. (1984), How to Use Damage Mechanics, Nuclear Engineering and Design, Vol. 80Lemaitre, J. (1996), A Course on Damage Mechanics, SpringerSimo, J.C.; Ju, J.W. (1987), Strain and Stress Based Continuum Damage Models, Int. J. Solids Structures, Vol. 23

Numerical simulation (Abaqus/Explicit)

Pressure vs timePmax = 0.63 MPa

Slab without aluminum coating (concrete B30)

Final distribution of damages (red colour – totally damaged material). Contours for t = 0.27 s

C

A

B

Concrete B30 – damage in tension (DT)

Without coating Short coating Large coating

Concrete B30 – displacements (point A)

red – without coating (exp. – 5.1 cm)blue – short ctg (exp. – 4.0 cm) green – long ctg (exp. – 3.2 cm)

Concrete B30 – displacements (point B)

red – without coating; blue – short ctg; green – long ctg

Concrete B100 – damage in tension (DT)

Without coating Short coating Large coating

Concrete B100 – displacements (point A)

red – without coating (exp. – 2.1 cm);blue – short coating (exp. – 1.8 cm); green – long coating (exp. – 1.6 cm)

Concrete B100 – displacements (point B)

red – without coating; blue – short ctg; green – long ctg

Concrete B100 – energies vs time (plate without coating)

red – dissipated energy; blue – kinetic energy

Concrete B100 – energies vs time (plate with short coating)

red – dissipated energy (plate); blue – dissipated energy (foam); green – kinetic energy (plate)

Concrete B100 – energies vs time (plate with large coating)

red – dissipated energy (plate); blue – dissipated energy (foam); green – kinetic energy (plate)

CONCLUSIONSCONCLUSIONS

�Thick layers of materials developed to absorb the large amount of energy can be easily applied on the structure;

�The influence of the protective coating is significant for „weaker” structures (in this case – concrete B30);

�For large, thin concrete plates only the relatively small part of blast energy can be absorbed by the protective coating, because of their mechanism of damage;

�Future research should include also other types of protective coating: honeycomb layers, additional layers of concrete, etc.;

�Numerical simulation enables to study a great variety of possible configurations structure - protective coating.