AnalysisAnalysis of of ReinforcedReinforced ConcreteConcrete

StructuresStructures SubjectedSubjected toto BlastBlast LoadingLoading

S. S. KarapinarKarapinar, I. , I. SanriSanri, G. Altay, G. Altay

Workshop Prague, March 30Workshop Prague, March 30--31, 200731, 2007COST Action C26COST Action C26

AimAim of of thethe StudyStudy

AnalyzeAnalyze thethe structuresstructures underunder thethe effectseffects of of blastblastloadingloading..

IncludingIncluding; ; thethe threatthreat definitiondefinition, , blastblast wavewaveparametersparameters, , dynamicdynamic propertiesproperties of of materialsmaterials andanddamagedamage assessmentassessment..

Definition of Blast LoadingDefinition of Blast Loading

Blast loading may result from the detonation of high Blast loading may result from the detonation of high explosives, chemical ammunitions.explosives, chemical ammunitions.

Type of extraordinary dynamic load and it has to be Type of extraordinary dynamic load and it has to be described by two parameters; peak overpressure described by two parameters; peak overpressure and duration.and duration.

Blast loading is a function of : Distance of the Blast loading is a function of : Distance of the structure from the explosion, and the charge weight structure from the explosion, and the charge weight or a weapon size.or a weapon size.

FormationFormation of a of a BlastBlast WaveWave

Variation of pressure within a shock wave (Variation of pressure within a shock wave (Fertis,1973, Dynamics And Vibration Of Structures)

Threat Threat DefinitionDefinition

Charge Weight Charge Weight oror weapon size (W) :weapon size (W) : W is expressed in weight or W is expressed in weight or mass of TNTmass of TNT ; the equivalent W of any other explosive material is ; the equivalent W of any other explosive material is based on experimentally determined factors or the ratio of its based on experimentally determined factors or the ratio of its heat of detonation to that of TNT.heat of detonation to that of TNT.

StandStand--offoff DistancesDistances (R) :(R) : R measures how close to the building a R measures how close to the building a bomb could explode and is therefore a function of the physical bomb could explode and is therefore a function of the physical characteristics of the surrounding site.characteristics of the surrounding site.

General General OverviewOverview of of BlastBlastLoadingLoading

DynamicDynamic BehaviourBehaviour of of MaterialMaterialUnderUnder BlastBlast LoadingLoading

WhenWhen thethe concreteconcrete is is strainedstrained;;

TheThe resistanceresistance increasesincreases linearlylinearly withwith deflectiondeflection untiluntil thethereinforcingreinforcing barsbars yieldyield..

TheThe deflectiondeflection is is increasingincreasing but but thethe resistantresistant remainsremains constantconstantuntiluntil at a at a deflectiondeflection correspondingcorresponding toto a a supportsupport rotationrotation of 2of 2°°

At a At a deflectiondeflection correspondingcorresponding toto a a valuevalue of of aboutabout 44°° thetheelement element willwill loselose itsits structuralstructural integrityintegrity andand fail.fail.

DynamicDynamic StrengthStrength IncreaseIncrease

Effects of strain rate on stressEffects of strain rate on stress--strain curve for concretestrain curve for concrete ((RefRef: TM 5: TM 5--1300)1300)

DynamicDynamic IncreaseIncrease FactorFactor (DIF)(DIF)

DIF is DIF is equalequal toto thethe ratioratio of of thethe dynamicdynamic materialmaterial strengthstrength toto staticstaticstrengthstrength..

DIF is a DIF is a functionfunction of;of;

StaticStatic materialmaterial strengthstrength : : IfIf thethe staticstatic strengthstrength of of materialmaterial is is highhighthenthen thethe increaseincrease in in dynamicdynamic strengthstrength willwill be be lowlow..

StrainStrain rate : rate : IfIf thethe materialmaterial is is strainedstrained rapidlyrapidly thenthen thethe increaseincrease in in dynamicdynamic strengthstrength willwill be be highhigh..

DeformationDeformation LimitsLimits

TheThe controllingcontrolling criteriacriteria in in thethe blastblast--resistantresistant designdesign is a limit on is a limit on thethe deformationdeformation oror deflectiondeflection of element.of element.

TwoTwo methodsmethods forfor evaluationevaluation of of structuralstructural responseresponse ::

DuctilityDuctility ratioratio

SupportSupport rotationrotation

CaseCase StudyStudy

TheThe analysisanalysis of of thethe structuralstructural elementselements underunder blastblastloadingloading withwith a a givengiven chargecharge weightweight andand standstand--offoffdistancedistance..

TheThe investigationinvestigation of of thethe damageddamaged systemsystem whichwhichcontainscontains thethe analysisanalysis of of thethe systemsystem withwith membermemberremovedremoved accordingaccording toto thethe explosionsexplosions..

AnalysisAnalysis of of StructureStructure underunder BlastBlastLoadingLoading

Charge Charge weightsweights areare 500 kg , 750 kg , 1000 kg 500 kg , 750 kg , 1000 kg andand1500 kg of TNT.1500 kg of TNT.

StandStand--offoff distancedistance is is consideredconsidered as 6m. as 6m. whichwhich is is thetheclosestclosest pointpoint toto thethe buildingbuilding accordingaccording toto thethe plan plan configurationconfiguration of of thethe buildingbuilding..

Location of explosion to the buildingLocation of explosion to the building

BlastBlast LoadLoad ParametersParameters

BlastBlast AnalysisAnalysis of of StructuralStructuralFrameFrame

TheThe frameframe membersmembers on on whichwhich thethe planeplane is is subjectedsubjected toto explosionexplosion directlydirectly areare takentaken intointoconsiderationconsideration seperatelyseperately..

An element An element loadedloaded byby a a blastblast can be can be modeledmodeled as a as a dynamicdynamic systemsystem withwith a a singlesingle degreedegree of of freedomfreedomcorrespondigcorrespondig toto itsits midmid--spanspan deflectiondeflection..

TheThe responseresponse of of thethe element is element is determineddetermined usingusingABAQUS, ABAQUS, finitefinite element program, element program, whichwhich containscontainsgeometrygeometry andand materialmaterial nonnon--linearitylinearity. .

viewview of of thethe xx--z z planeplane whichwhich is is subjectedsubjected directlydirectly totothethe explosionexplosion

ModellingModelling of of thethe ElementElement

Structural frames are modeled using solid, homogenous Structural frames are modeled using solid, homogenous element.element.Mesh design is a relatively fine mesh which provides Mesh design is a relatively fine mesh which provides moderate accuracy. moderate accuracy. The material is concrete (Young’s The material is concrete (Young’s modulmodulusus of 28500Mpa and of 28500Mpa and Poisson’s ratio of 0,2) Poisson’s ratio of 0,2) The plasticity stressThe plasticity stress--strain curve is increased by the D.I.F strain curve is increased by the D.I.F The pressureThe pressure--time load values are defined by applying to the time load values are defined by applying to the surface of the surface of the element.element.

Blast Blast AAnalysisnalysis of of CColumnolumn SB121 SB121 SSubjectedubjected

to 500kg of TNT to 500kg of TNT EExplosionxplosion

W=500 kg of TNT , R=6,16m. W=500 kg of TNT , R=6,16m. andand Z=0,78 (m/kgZ=0,78 (m/kg1/31/3))PPsoso=1,54 =1,54 MpaMpaPPrr=9,405 =9,405 MpaMpattoo=0,008 =0,008 secsec..

BlastBlast loadingloading of of columncolumn SB121 SB121

0

2

4

6

8

10

0 0,005 0,01Time (sec.)

Ave

rage

pre

ssur

e (M

pa)

Outsidepressureinsidepressure

AnalysisAnalysis ResultResult

MaxMax--stressstress distributiondistribution ColumnColumn midmid--pointpoint deflectiondeflection

Damage AssessmentDamage Assessment

If the support rotation of the element is exceeded If the support rotation of the element is exceeded 44°°, then it is said to be failed. By this way, three , then it is said to be failed. By this way, three models are considered with the member removed models are considered with the member removed according to the results are taken from the according to the results are taken from the AAbaqusbaqusprogram. program.

The rest of the system is analyzed according to the The rest of the system is analyzed according to the vertical loads by using SAP2000 package program.vertical loads by using SAP2000 package program.

TheThen n thethe capacities of the rest of the structural capacities of the rest of the structural frames are checked to be the limitframes are checked to be the limit oror not.not.

TheThe AnalysisAnalysis of of thethe DamagedDamagedSystemSystem

Model 1 Model 1 duedue toto 750 kg of TNT 750 kg of TNT

Model 2 Model 2 duedue toto 1000 kg of TNT1000 kg of TNT

Model 3 Model 3 duedue toto 1500kg of TNT1500kg of TNT

ThreeThree damagedamage scenariosscenarios areare preparedprepared..

DamageDamage ScenariosScenarios

KB122, KZ16, KN116, KB123, KZ17, KB124, KZ18, KN118, KB137, KZ31, KB142, KZ36,

KB149

SB120, SZ20, SB121, SZ21Model 3

KB122, KZ16, KB123, KB124, KZ18, KB137,

KB142

SB121, SZ21, SB120Model 2

KB122, KB124, KZ18, KB142SB121Model 1

Removed BeamsRemoved ColumnsDamagedScenario

Model Model 33 PP--M interaction of column SN121, SN221, SN321 in M interaction of column SN121, SN221, SN321 in yy--directiondirection

-1500,00

-1000,00

-500,00

0,00

500,00

1000,00

1500,00

2000,00

2500,00

3000,00

3500,00

-800,00 -600,00 -400,00 -200,00 0,00 200,00 400,00 600,00

M (Knm)

P (K

n)

P-M interactionP-M interactionBalance LimitSN121SN221SN321

SummarySummary of of ResultsResults

KB 119, KB 138, KB141, KB143, KB121, KB120,

KZ25, KZ32, KZ35, KZ37, KZ15, KZ43, KN115,

KN125, KN132, KN135, KN137, KN143, KN217, KN218, KN225, KN235, KN237, KN238, KN325, KN335, KN337, KN343

SN120, SN220, SN320, SN121, SN221, SN321

KB122, KZ16, KN116, KB123, KZ17, KB124, KZ18, KN118, KB137, KZ31, KB142, KZ36,

KB149

SB120, SZ20, SB121, SZ21Model 3

KB 119, KB 138, KB141, KB143, KB121, KZ32,

KZ35, KZ37, KZ15, KN116, KN118, KN135, KN137, KN143, KN216, KN218, KN235, KN237, KN238, KN316, KN317, KN318, KN335, KN337

SZ20, SN120, SN220, SN121, SN221, SN321

KB122, KZ16, KB123, KB124, KZ18, KB137,

KB142

SB121, SZ21, SB120Model 2

KB 119, KB 138, KB141SB120, SZ20, SZ21, SN121

KB122, KB124, KZ18, KB142SB121Model 1

Damaged BeamsDamagedColumns

RemovedBeams

RemovedColumns

DamagedScenario

ConclusionConclusion

According to the results, the system affects significantly when According to the results, the system affects significantly when the the charge weight increases. But the actual charge weight of explosicharge weight increases. But the actual charge weight of explosive ve used by the terrorist, the efficiency of the chemical reaction aused by the terrorist, the efficiency of the chemical reaction and the nd the source location are not reliably predictable.source location are not reliably predictable.

The standThe stand--off distance is the key parameter that determines the off distance is the key parameter that determines the blast pressure so for protecting a structure is to keep the bombblast pressure so for protecting a structure is to keep the bomb as as far away as possible by maximizing the standfar away as possible by maximizing the stand--off distance.off distance.

Blast has a characteristic of high amplitude. The results showedBlast has a characteristic of high amplitude. The results showed that that if the member subjected to high pressure, they could cause big if the member subjected to high pressure, they could cause big deformation on the element and cause to be exceed the support deformation on the element and cause to be exceed the support rotation so the elements which are close to explosion are damagerotation so the elements which are close to explosion are damaged d and failed. and failed.

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