Demolishing of concrete structures

This presentation contains basic demolishing techniques of concrete structure both manual and mechanical methods supported with photographic illustration.

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By TsegayeArega
M Tech student in Construction
Engineering and Management
IIT Delhi
April 2018
DEMOLISHING OFCONCRETE
STRUCTURES

2. INTRODUCTION
Demolitionisthedısmantlıng,razıng,
destroyıngorwreckınganybuildingorstructure
oranypartofbuildingbypre-plannedand
controlledmethods.
Demolitionisbringingdownthebuildingand
otherstructuressafely
Demolitionisoneofthemostdangerous
activitiesintheconstructionsector
DemolitionCanbetotalorpartial
Totaldemolitionisaimedattherecoveryofthe
areaforsubsequentre-use,whilepartial
demolitionisaimedattherecoveryofthe
buildingforrefurbishingorrebuilding.
.
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3. Thestructureswhichhavealreadypassedtheir
designlifeneedtobereconstructed,forsafetyand
operationalrequirements.
Theoldstructuresneedtobedemolishedfor
replacementbynewstructures
Smallstructurescanbedemolishedbymanual
methods but machinery and
advancedtechniquesarerequiredfordemolitionof
biggerstructures
Advancedtechniquesarealsorequiredforfaster
demolitionanddemolitioninconfinedareas.
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WHYDEMOLISHING?

4. Demolitionworkistobeperformedsafelyand
withnumberofdifferentstepsinvolvedbefore
andduringtheexecutionofademolition
process.
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STEPSBEFOREDEMOLITION

5. For demolition of a building ,detailed survey
and assessment of a building is necessary.
It includes
A. Building survey
Drawing records
Material survey
Hazardous materials
Photographs of a building to be demolished
Surrounding buildings
Building height, distance from nearby buildings
Type of building
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1. SURVEYFORDEMOLITION

6. B. Structural survey
Drawing records
Special structure
Behavior of structure
Structural support system
Degree of deterioration
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1. SURVEYFORDEMOLITION

7. a.AsbestosContainingMaterial
Inthecasewhenasbestos
containing material are
discovered,specialistcontractor
shallbeemployedtoremovesuch
asbestoscontainingmaterial.The
asbestoswasteshouldbehandled,
storedanddisposedofaschemical
wasteinaccordancewiththe
Waste Disposal Regulation
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2. REMOVALOFHAZARDOUS MATERIALS
Asbestos Material

8. Inthecasewhenpossiblesoil
contamination material is
present,specialistshallbe
employed topreparesoil
contaminationtestproposaland
submitsuchproposaltothe
Environmental Protection
Department forcomment.
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2. REMOVALOFHAZARDOUS MATERIALS
b. Soil Contamination Material
Soil contamination

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3. PREPARATION OFPLAN
Basedondemolitionsurveys,ademolitionplanis
preparedThisplanisproducedwiththeapplicationfor
approvaltothelocalauthority.Thisplanincludes
Planshowingthelocationofabuildingtobe
demolished.
Buildingheight,structuralsystem
Extentofdamagetothebuilding
Existingstructuresandfacilitiesinthevicinity
Layoutplan
Proposedmethodofdemolition
Safetymeasures
Proposed sequence of demolition steps
Details of equipment's used.
plan for handling and disposal of debris
Proposed arrangements for site supervision

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4. SAFETYMEASURES
TrainingandCommunication:
Demolitionworkers,including
plantorequipmentoperators,
shallgothroughproperjobsafety
trainingandbeinformedofthe
potentialhazardsbyattending
trainingsessionsaswellason-the-
jobtraining
Equipment Maintenance:
Allequipmentshallbetestedand
examinedbeforeuse.Theyshallbe
properlystoredandmaintained.
Theequipmentshallbeinspected
dailyandresultsoftheinspection
shallberecordedaccordingly.

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4. SAFETYMEASURES
Aproperlyconnectedpowersourcefromalocalelectricutility
supplieroramobileelectricitygeneratorshallbeutilizedin
demolitionsites
Allflammablegoodsshallberemovedfromsiteunlessthey
arenecessaryfortheworksinvolved.Anyremaining
flammablegoodsshallbestoredinproperstoragefacilities.
Allfurniture,timber,doors,etc.shallberemovedbeforeany
weldingworkisperformed.Firefightingappliancesshallbe
providedandmaintainedinworkingconditions.
Electrical Safety
Fire

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DEMOLISHINGSEQUENCE
DemolitionsequenceshallbedeterminedbasedonActualsite
conditions,Restraints,Thebuildinglayout,TheStructural
layoutanditsconstruction.Ingeneral,thefollowingsequence
shallapply:
Utilitiesdisconnection.Electricity,plumbingwaterlines,
drainageconnectionsetc..
Allcantileveredstructures,canopies,verandahsand
featuresattachedtotheexternalwallsshallfirstbe
demolishedpriortodemolitionofmainbuildingandits
internalstructuresoneachfloor

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DEMOLISHINGSEQUENCE
Whendemolishingtheroofstructure,allliftmachinerooms
andwatertanksathighlevelshallbedemolishedin“top
down”sequencetothemainrooflevel
Demolitionofthefloorslabsshallbeginatmidspanand
worktowardsthesupportingbeams.
Floorbeamsshallbedemolishedintheorderof
cantileveredbeams,secondarybeamsandthenmainbeams.
Non-loadbearingwallsshallberemovedpriorto
demolitionofloadbearingwalls.

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DEMOLISHINGSEQUENCE
Ifsiteconditionspermit,thefirstfloorslabdirectlyabovethe
groundfloormaybedemolishedbymachinestandingon
ground.

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FACTORSAFFECTING DEMOLISHING METHODS
AccordingtoKasaietal/1988/aredemolitionmethods
classifiedintoprinciplesandmechanismsofbreaking.
Theselectionofaspecificprocessshouldbebasedonthe
experiencelearnedfromtheconventionaldemolition
industry,andapplicableexperiencefromactual
decommissioningprograms.
Someofthefactorstoaffectingselectionof
demolishingmethodsare;
a)Type of structure
Different types of structure like load bearing masonry
structure , RCC framed structure, steel structure , etc.

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FACTORSAFFECTING DEMOLISHING METHODS
b.Size of structure
If the size of structure is small, hand demolition can be
sufficient. for large structures and multi storied buildings
special like wrecking ball method, deliberate collapse,
implosion technique etc are necessary.
c.Available time period
d.Location of structure
e.Limitation of noise, dust and vibrations
f.Skill of workers
g.Safety
h.Availability of equipment
i.Adjacent structures

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FACTORSAFFECTING DEMOLISHING METHODS
Demolishing
Techniques
Engineering
Demolishing
Mechanical
method
Implosion
Method
Deconstruction
Method
Non
Engineering
demolishing
Manual
demolition

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CONTINUED…
ManualMethods
Thisisdemolishingbyhumanoperatives/handheld
operations.
Suitableforuseinsmallersitewithcongestedspacewhere
largermachinecannotbeemployed.
usingsimpleelectricallyorpneumaticallypoweredtoolssuch
aspicks,hammers,wirecuttersorhanddrivenhydraulic
jacksetc.tocarryoutthedemolitionofindividualelements.
Tools required for manual demolition;
•Hammers
•Picks
•Wire cutters
•Welding cutters
•Hand driven hydraulic jacks etc.

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Mechanical Methods
Wrecking method
Pusher arm technique
Thermic lance technique
Non explosive demolition
Concrete sawing method
Deliberate collapse method
Pressure jetting method
bursting
Implosion Methods
demolition of structure with the help of explosives is called
as implosion
CONTINUED…

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Manual methods arecarriedouttopdown,
proceeding,ingeneral,fromtherooftoground.Thesequence
ofdemolitionmayvary,dependingon
Siteconditionsand
Structural element to be demolished
1. MANUALMETHODS

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1.Handheldhammering;Repeatedhammeringisoften
usedtofractureandbreakconcretemainlyduetooccurring
tensileandshearstress.
1. MANUALMETHODS
i.Rotary-hammer ;boringholesby
Rotaryhammering;inconcrete.They
areversatileandalsoworkwellinthe
hammer-onlymode.
ii.Chippinghammer;Lightweightand
hand-held,chippinghammers are
perfect for breaking
verticalandoverheadconcretesurfaces.

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2.Hydraulic concretecrusher
Hydraulicconcretecrushersare
usedtoreduceconcreteinto
smaller,moremanageablepieces.
They alsoseparate steel
reinforcementfromconcrete.
1. MANUALMETHODS
iii.Demolition hammer;
Demolition hammers deliver hammering action
only, unlike rotary hammers, which are used to
bore holes.

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3.Pavementbreaker
Pavementbreakersareusedin
heavyconcretedemolitionprojects
becausetheycandemolish
pavements,roads,andextremely
thickconcrete
3.Hydraulicsplitter
Hydraulicsplittersuselateral
forcesagainsttheinsidesof
concreteholestobreakupthe
concrete without creating
lotsofnoiseanddebris.
1. MANUALMETHODS

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Thesequenceofdemolitionbymachineistypicallythe
sameasthetopdownmanualmethod,exceptthat
mostofthedemolitionisdonebymechanicalplant
2. MECHANICAL METHODS
1. Excavator and attachments

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2. MECHANICAL METHODS
1.1 Excavator mounted with hydraulic
crasher
•Thecrusherattachmentbreaksthe
concreteandthereinforcementbythe
hydraulicthrustthroughthelong
boomarmsystem
•Thehydrauliccrushercanbe
operated from
thegroundoutsidethebuilding.This
methodisalsosuitablefordangerous
buildings,silosandotherindustrial
facilities.
•Theexcavatorshalloperateonfirm
groundthatcansupportthemachine
duringthecrusheroperation.
•Eachsectionofthestructureshallbe
demolishedinatopdownsequence

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1.2.ExcavatormountedwithA
hydraulicjackhammer;
Typicallymuch largerthan
portableones,maybefittedto
mechanicalexcavatorsorbackhoes
andiswidelyusedforroadwork,
quarryingandgeneraldemolition
orconstructiongroundwork.
Pneumaticbreakersaresimpler
toolswithfewermovingparts,
requiringlessmaintenance.
2. MECHANICAL METHODS

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The demolition begins with the lifting of the
mechanical plant on to the building top floor.
Adequate propping shall be installed at floor levels
below the working floor to safely support the operation of
the mechanical plant.
The movement of the mechanical plant shall only be
within the propped area. The propped areas shall be
suitably marked.
The mechanical plant shall be lifted onto the roof of the
building by the use of mobile crane or other appropriate
means as approved.
The machine shall descend down to the next floor by
means of a ramp. The ramp may be a temporary structure
or other appropriate design.
2. MECHANICAL METHODS

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2. MECHANICAL METHODS

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2. MECHANICAL METHODS
2. Ball and crane
Thisisoneoftheoldestandmost
commonly usedmethods for
demolition.
Thewreckingballapplication
consistsofacraneequippedwitha
steelball.
Acraneusesawreckingball,
weighingupto6120kg,whichis
eitherdroppedontoorswunginto
theelementtobedemolished.
Concretememberscanbebroken
intosmallpieces,butsecondary
cuttingofreinforcingmaybe
necessary.

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2. MECHANICAL METHODS
Thedestructionofthebuildingisbytheimpactenergy
ofthesteelballsuspendedfromthecrawlercrane.The
wreckingballoperatesoutsidethebuilding.
However,theoperationrequiressubstantialclear
space.Theapplicationalsodemandshighlevelskill
operatorsand wellmaintained equipment

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2. MECHANICAL METHODS
Recommendedtechniquesforthewreckingball
operationsinclude(1)VerticalDrop-freefallingof
thewreckingballontothestructureand(2)Swing
inline-swingingoftheballin-linewiththejib.
Aseconddraglinewillnormallyconnecttotheball
horizontallytocontroltheballmotion
Theoperationshallnotbeperformedadjacentto
overheadpowerlines.Thesiteshallbeentirely
fencedofftoforbidpublicaccess.
Oneofthedisadvantageofthismethodishe
breakupprocesscancauseconsiderabledust,
vibrationandnoisewhichmaybeobjectionable.

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2. MECHANICAL METHODS
3.Dismantling
Selectiveorcompletedemolitionof
concretestructuresispossiblebycutting
elementsandthenremovingthemwitha
crane.
Thecuttingprocessmaybeby
sawing,waterjettingorthermal
lance.
Becausethesurfaceofthecut
concreteissmoothandrelativelyregular,
these methods have particular
applicationwhentheobjectiveispartial
demolition,forinstanceinthecreationof
openingsinwallsandslabs.
Dismantling a beam

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2. MECHANICAL METHODS
Continued…
Hydrodemolitionusesahighpressure
supersonicwaterjet,thatpenetrates
theporesandcracksoftheconcrete
andbuildsupaninternalpressure.
Whenthispressureexceedsthetensile
strengthoftheconcrete,theconcrete
breaks.
Thewaterjetcanbeusednotonlyfor
cuttingstraightlinesbutalsocontours,
ausefulfeatureforcuttingaccess
manholes.
Athermallanceiscreatedbypackinga
seamlessmildsteeltubewithlow
carbonrodsandpassingoxygen
through the tube.
Water jet cutting

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2. MECHANICAL METHODS
Continued…
Whilethismethodeliminatesvibration
anddustproblems,itcreatesother
hazardsassociatedwithsmokeandfire
danger.
Whethersawing,jettingorlancingis
usedtodismantlethestructureorits
components,eachelementmustbesafely
loweredtotheground.
Theamountoftimeandcostoflaborare
themaindrawbacks.
Toxicwastesuchasasbestossheetsand
leadpainthavenoresalevaluesothey
arediscarded.

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2. MECHANICAL METHODS
4. Pressure bursting
ocanbeusedincaseswhererelatively
quiet,dust-free,controlleddemolitionis
preferredThecuttingprocessmaybeby
sawing,waterjettingorthermallance.
oBothmechanicalandchemicalpressure
burstingsplittheconcrete,eitherwitha
splittingmachineoperatingonhydraulic
pressureprovidedbyamotorinthecase
ofmechanicalbursting,orthroughthe
insertionofanexpansiveslurryintoa
pre-determinedpatternofboreholesin
thecaseofchemicalbursting
Both methods work by applying lateral forces against
the inside of holes drilled into the concrete.

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5. EXPLOSIVES
Implosionisthestrategicplacingofexplosivematerialand
timingofitsdetonationsothatastructurecollapsesonitselfin
amatterofseconds,minimizingthephysicaldamagetoits
immediatesurroundings
Thetechniqueweakensorremovescriticalsupportssothat
thebuildingcannolongerwithstandtheforceofgravityand
fallsunderitsownweight.
Numeroussmallexplosives,strategicallyplacedwithinthe
structure,areusedtocatalyzethecollapse.Nitroglycerine,
dynamite,orotherexplosivesareusedtoshatterreinforced
concretesupports.
Forthedemolitionofconcretestructuresitisusualtodrillholes
atapredeterminedangleintotheconcretetoberemoved

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Theholesarethenchargedwithanexplosivewhichis
electricallydetonated
Despiteitsterminology,buildingimplosionalsoincludesthe
controlleddemolitionofotherstructures,suchasbridges,
smokestacks,towers,andtunnels
Empiricaljudgmentbasedontheskillandexperienceofthe
operatoristhebasisforblastingdesign.
Asimplerbutfarlesseffectivemethodofblastingistolay
theexplosivechargeontheelementtobedemolishedand
coveritwithsandbags.
Precautionsshouldbetakentostopflyingdebrisandinall
circumstancesstrictsitecontrolmustbemaintainedto
ensurethesafetyofworkersandthegeneralpublic.
5. EXPLOSIVES

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Pre blast considerations
Thedesignmayincludepre-weakeningofthestructure,the
strategyinplacementoftheexplosivesandtimedelayso
thatthebuildingwillcollapseinasafemanner.
Pre-weakeningofthestructuremayincludecuttingouta
portionoftheshearwallsandotherstructuralelements
Atestblastmaybeconductedtoverifythestrengthofthe
structuralmemberandtofinetunetheexplosivedesign.
Protection of the adjacent properties and habitats is also an
important consideration.
Concrete columns fully
loaded with explosives
CONTINUED…

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Test blast
Before carrying out the actual blasting, a test blast, in
ordered
to ascertain the efficiency of explosive & detonators.
The wrapping of holes can be done to ensure debris does not
fly in air due to explosion of charges.
Before After
CONTINUED…

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5. Explosives
General things
High Risk Factor
Time Taken
Produce Distortion
Expensive
Chances of error
Need of experts
Error may leads to
No demolition
Loss of life's
CONTINUED…

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Demolishingprestressedconcretestructurescanbe
moredifficultthandemolishingreinforcedconcrete
becauseoftheenergystoredintheprestressing
tendons.
Prestressingtendonsarelikesstretchedrubberbands,
withenergystoredinthestretchingprocess.
Thereleaseofthestoredenergyinarubberband
causesittosailthroughtheair.
Thetotaldemolitionofaprestressedpre-tensioned
structureisnomoredifficultthanthedemolitionofa
cast-in-place reinforce concrete structure.
DEMOLITION OFPRESTRESSEDCONCRETE

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Pre stressedpre-tensioned members are usually designed to
resist applied loading in only one direction.
Because of this, the members will fail rather easily if a force
can be applied in an opposite or lateral direction
The partial demolition of pre tensioned pre stressed structure
requires more care than similar operations on a cast in place
structure.
DEMOLITION OFPRESTRESSEDCONCRETE
Pre-tensionedslabsandbeams,or
smallerdismantledportions,maybe
liftedandloweredtothegroundas
completeunits(Asshowninthephoto).
Generally,anynecessaryshoringand
subsequentliftingshouldbefrom
pointsneartheendsoftheunits

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Safe,uneventfuldemolitionofrelativelylowstructures
usingacraneandaballhasbeenaccomplishedwherethereis
adequatesurroundingworkspace.
Disassemblyorfrom-the-top-downdemolitionrequiresa
largeamountofshoringwhichmustbeinstalledalongthe
entirelengthofthemembers,unlessintermediatetendon
anchorswereinstalledduringconstruction.
Onceshored,theslabandbeamscanbedetensioned—inre
verseorderinwhichtheyweretensioned.Thentheslabsand
beamscanbedemolishedusingthosemethodspreviously
described,withtheexceptionoftheball-and-cranemethod.
Thepartialdemolitionofanunbondedpost-tensioned
structurecanbeverycomplicatedandhazardous.If“as-
built”drawingsarenotavailable,thisoperationcanbeeven
more complex.
DEMOLITION OFPRESTRESSEDCONCRETE

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DEMOLITION OFPRESTRESSEDCONCRETE
After the shoring is in place, the tendon and reinforcing bars
a re located using magnetic detection devices.
Once this is done, careful drilling,
chipping or sawing may be used to
expose the pre stressing tendons
(Photo B).
The concrete can then be bro k e n
with either hand-held or machine
mounted breakers, or once completely
severed, reduced to a size which may
be lifted and lowered .
Careful planning by competent
persons experienced in post tensioning
is essential before attempting partial
demolition ofpost-tensioned structures

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TOPICREFERENCES
1.Christer Molin,1996,Demolition techniques,IABSE congress
report, Stockholm Sweden
2.Hal T. Hudgins, Demolition of Concrete Structures ,
demolition specialists Atlanta, Georgia
3.Ravi Patel ,Demolition Method & Techniques , International
Journal of Advanced Research in Engineering, Science and
Management (IJARESM), Umrakh, Gujarat, India
4.Thomas S. LaGuardia, P.E., Concrete Decontamination And
Demolition Methods, Nuclear Energy Services, Inc. Danbury,
Connecticut.
5.Prof. Ankit Pate, Demolition of Structures, BITS Edu
Campus
6.Martin Johansson, 2002, Handbook on Demolition with
Brokk , Managing director of Brokk AB, Skellefta.

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