WELCOME to CHAKA Construction 

Introduction

 

CHAKA CONSTRUCTION is one of the leading construction companies in Bangladesh. Working in Construction of High rise and low rise building construction, Retrofitting construction in Garments factory building, Residential and commercial building also execute various types project planning and management for both the RCC and steel structure.

CHAKA CONSTRUCTION started their activities above those sectors since 2003.We have our own Engineering team, who are able to make flexible and readily adjustment to any structural segment work, implementation civil construction, Retrofitting works construction, RCC & Steel Structure works. We offer general contracting, construction management, and preconstruction planning services for projects of all sizes single office fit-up to treatment plants.

CHAKA CONSTRUCTION well respected position in the infrastructure and construction industry has been an accomplishment of sheer commitment and dedication to building long term relationships based on integrity, performance, value, workmanship and client satisfaction.

Examples our activity:

  • Infrastructure development
  • Civil work
  • Industrial facilities
  • Commercial complex building
  • Education & Campus building
  • Hospitality & Resort
  • Manufacturing & Industrial building
  • Water Treatment plants
  • Residential complex etc.

We are a 100% employee-owned company whose daily actions are guided by our core values. Our commitment to outstanding job completion, exceptional customer service and superior safety performance has made us a partner of choice in the construction industry.

 VISION

  • Our main goal is to set a benchmark in the professional field.
  • Always committed to be innovative and maintain quality in order to meet the needs of our clients.

MISSION

  • To provide International standard services using best talents from home and abroad.
  • We are committed to work professionally and ethically with our honorable clients delivering quality services for the development of viable successful and sustainable projects.
  • We are committed to develop high-end technology solutions with constant innovation, continuous Improvement and value added services.
  • To develop and deliver value system to the clients with quality and reasonable cost with a focus on rapid progress.

 

OUR AREA OF ACTIVITIES:

 

  • Project Management
  • Civil Construction (Steel Structure & RCC Building)
  • Retrofitting Structure Construction & Design
  • Water Retaining Structures: Sewage and water treatment plants
  • Road Structures: Retaining Walls, Bridges, Barriers& Embankment
  • Industrial, Commercial and Residential Buildings
  • Filling and Compaction of Foundations & PlatformsforBuildingsandCivil Structures
  • Interior Design & Construction
  • Fire Safety System Construction

 

 OUR SPECIALIZATIONS:

  • Having huge work experience in Project Management and Construction, Using modern test instruments andHigh quality workmanship.
  • Professional and experienced management, supervision and workforce.
  • High-specification components
  • Independent oversight, monitoring and checking; and
  • A dedicated methods team and the research and development team constantly review existing methods to determine best practice and work on identifying new methods.

 

RETROFITTING WORK PROCEDURE

CHAPTER1.GENERAL

Thispartofthemanualcoversonlytheconstructionoftheretrofittingworks.Nodesignofretrofitting isdiscussedin thismanual.Itissuggestedthattheretrofittingdesignofanexistingbuildingshallbe carriedoutbyaqualifiedstructuralengineer.HemaytakenecessaryguidelinefromtheSeismicRetrofit Design of Existing as per Building Code. The retrofit construction work shall  be implemented as per retrofit design through the material specificationandworkprocedurewill be Bangladesh National Building Code.

Incomparisonwithgeneralbuildingconstructionwork,retrofittingworkisgenerallycarriedout undersome restrainedconditions.Because,inmostofthecases,thisconstruction hastobedoneon buildingsthatarein use.Sotheworkshallbedonepartbypartwithinatimelimitconsidering environmentalissues suchasdustandnoisecontrol.

Sufficientmeasuresshallbetakenforthesafetyoftheoccupantsandusers.  Inaddition,special attentionhastobegivensothatthe buildingservicesare notinterrupted duetoconstructionwork. Moreoveritshallbeensuredthatthereisnodamageinutilityservicelinessuch aselectricline,gas line,waterlineetc.

Anadequate'ConstructionPlan'forretrofitting workshallbedonewiththefollowingconsiderations:

 

  • Limitedaccesstothebuildingandpartbypart Construction.
  • Reductionoftimeperiod
  • Minimumdustandnoisecontrol.
  • Adequatesurveyofexistingpipingandelectricalwiringsystem,ensuringsafety.

 

CHAPTER 2.MATERIALS

The selection of the right materials tobe used in the seismic retrofitting of a given  structure consideringthequality,availability,suitabilitytothelocalconditionhasbeenamajorchallenge.The selectionofmaterialstobeuseddependsonmanyaspectsincluding applicabilityandsuitabilityof materials forthe target structures. Using standardandinnovativeretrofit materials, appropriate technology, workmanship,andqualitycontrolduringimplementationarethekeyfactorsfora successfulrepair,strengtheningandrestorationofvulnerableordamagedstructures.

Someofmaterialsthathavebeenusedforseismicretrofittingin differentseismic retrofittingmethods arespecializedanddifferentfromtraditionalmaterialswhicharenormally usedfornewbuilding construction.Inthesesectionmaterialsthatarespecially usedforseismicretrofitconstructionhave been discussed.  Formaterialsthat arecommonfor seismicretrofitting as  wellasnewbuilding construction,specificationsinBNBC shallbeused.

2.1    CONCRETE

Thecementandfineaggregatestobeusedinconcreteforseismicretrofitting workarethesameasused fornewbuildingconstructionandthespecificationinBNBC.Butforcoarseaggregateitis desirabletouseaslightlysmallerdiameterthanwhichhasbeen usedfornewbuildingconstructionastherearemajorrestrictions onconcretecastingandconsolidation inretrofittingwork.

2.2      STEELREBAR

Steelrebarmaterialshallbethesameasusedfornewbuildingconstructionandspecificationshallbeas indicatedin BNBC.

2.3       ADMIXTURE

Mortarandconcretetobeusedforretrofittingworksarerequiredtohavegoodworkability, higher strengthwhileaggregatemusthaveminimalsegregationandvoids,aswellasminimalwatercontent. Toensurethese,innormalsituationswaterreducingadmixturemaybeused.

 

Themajorreasons for usingadmixturesinretrofitconstruction concreteare:

•    Tomaketheconcreteworkableintherestrictedarea.

•·Toensurepropercompactioninrestrictedarea.

•    Tomaintainthequalityofconcreteduringthestagesofmixing,transporting,placing,and curinginadverseweatherconditions.

•   Toovercomecertainemergenciesduringconcretingoperations

 

Despitetheseconsiderations,itshouldbeborneinmindthatnoadmixtureofanytypeoramountcan beconsideredasubstitute forgoodconcretingpractice.Theeffectivenessofanadmixturedepends uponfactorssuchastype,brand,andamountofcementingmaterials;watercontent;aggregateshape, gradation, andproportions;mixingtime;slump;andtemperatureoftheconcrete.

Admixturesbeingconsideredforuseinconcreteshouldmeetapplicablespecificationsasin ASTM C494(TypeAtoTypeG)alongwithBDSEN934-1:2008forconventionalmixes,ASTMC260for Air-entrainingadmixturesandASTMClO17forflowingconcrete.Trialmixturesshouldbemadewiththe admixturesandthejobmaterialsattemperatureandhumidityanticipatedonthejob.Inthiswaythe compatibilityoftheadmixturewithothertypeadmixturesandjobmaterials,aswellastheeffectsof theadmixtureonthepropertiesof thefreshandhardenedconcrete,canbeobserved.Theamountof admixturerecommendedbythemanufacturerortheoptimumamountdetermined bylaboratorytests shouldbeused.

 

2.4 NON-SHRINKGROUT

Forthepurposeofspecifications,"non-shrinkgrout" canbedefined asahigh-strengthmortarorgrout whichdoesnotshrink intheplasticstate,is dimensionallystableinthehardened,andbonds permanentlytoacleanmetalplateandconcretesubstrate.Retrofitconstructionlikecreatingwallsinsideexistingframes,gapsbetweenexistingconnectionsand attachedsurfacescaneasilybeopenduetodryingshrinkageoftheconcrete.Itisimportantto usenon shrink concreteinthiscontextintheselocations.

 

2.4.1      Materials

Non-shrink,non-metallic,non-corrosive cement-basedgroutshallconformtothefollowing requirements:

•    ApplicableStandards:ASTMCl107

•      Groutshallbemanufacturedspecificallyforuseinsupportingheavy loads(loadsinexcess of300poundspersquarefootconcentratedloador100poundspersquarefootuniformload).Grout:   ASTMCl107,GradeA,B,orC,asappropriatefor theconditionor circumstance.

•     Shrinkageat28days:Noshrinkagebeforehardening(0.00shrinkagewhentestedin accordancewith ASTMC827);noshrinkageafterhardening(0.00 shrinkagewhentestedin accordancewithASTMC827).

•    Compressivestrength,minimum:

a)  At seven days: 3500psi

b)  At28days:    5000psi.

•    Initial settingtime,afteradditionofwater:approximatelyonehourat70

DegreesF.

•    Flowabilityshouldbeensured asnecessaryfortheparticularapplication.

2.4.2      Submittals

a)  ProductData:   Submitmanufacturer'sproductdataandinstallationinstructions.

b)  Certification:Submit certificatesofcomplianceorlaboratorytestreportswhichindicate thefollowing:

•  Materialsusedinthegroutarefreefrommetalliccomponents andcorrosion-producing elements.

•    Materialsmeetspecifiedshrinkageandcompressivestrengthrequirements.

 

 

2.5 MICRO CONCRETE

ForrepairsectionsgenerallydeeperthanlOOrnmitmaybenecessaryto mixthenon-shrink grout(see section2.6) withproperlygraded5rnmto12rnmsilt-free aggregatetominimizetemperaturerise.The quantityofaggregaterequiredmayvarydependingonthenature andconfigurationoftherepair location.Thetypicalresultswith afewaggregateproportions,forvariousapplicationsarefurnished belowforguidelines.

Nonshrink GroutPowder:Coarse Aggregate(SSD)(Byweight) = l:  0.75

 

Water:Powderratio(Byweight)=0.16(shallnotbeincreasedinanycircumstances).

Table2.7.1     Compres sivestrength of Micro Concrete

Compressive strength(Nhnm2}

(Testedon70.7mmcubesasperBS4551-80)

 

10

30

70

280

10

30

40

5

Tensilestrength                        2.0N/mm2@28days

Themicroconcretein theflow ableconsistencyshouldachieveacompressivestrengthofnotlessthan

1ON/mm2  after24hours,40N/rnm2after7daysand50N/rnm2after28daysat

300C.Mostimportantly,thecuredmicro-concreteshall containnometallic aggregates,orchlorides andshallbeshrinkagecompensatedintheplasticstate. Theunrestrainedexpansionshallbebetween1-4%.Theflexural strengthshallnot belessthan5N/mm2@28days.Themicro-concreteshallhave a coefficientofthermalexpansionsimilartothatofthehostconcrete.ThemixeddensityofMicro-concreteshallexceed2100kg/m'at27°C.

 

2.6 BONDINGAGENTFOROLDCONCRETE TONEWCONCRETE

Freshwetconcretedoesnotnormallybondwelltoexistingdryconcrete. Soitisusualto apply bondingagentonoldconcretebeforelayingnewconcreteandbondingfresh,plasticconcretetoold, hardenedconcreteincreasesthestrengthofthecompositematerial.Freshpatches,concreteadjacentto constructionjoints,andoverlaysallbenefitfrombondingtothehardenedconcretesubstrate.Bondis not,however,guaranteed.Itmustbeensured throughpropersurfacepreparation,materialchoiceand use,andcuring.Ignoringoneofthesecomponents mayresultinthetotallossofbond.

Materialspecificationshallconformto

•    ASTMC1059:StandardSpecificationforLatexAgentsfor BondingFreshto HardenedConcrete.

•      ASTMC1583:StandardTestMethodforTensileStrengthofConcrete SurfacesandtheBond StrengthorTensileStrengthofConcreteRepairandOverlay MaterialsbyDirectTension(Pull offMethod).

•    ACI503R-80:UseofEpoxyCompoundwith Concrete.

 

2.7 ANCHORING  ADHESIVE  FORPOST-INSTALLED  ANCHOR

Adhesivetobeusedforanchoringstud-type anchorsconsistingofthreadedsteelrod,nut,andwasher ordeformedreinforcing baretc.asindicatedindrawingsandspecificationsshallbeepoxyadhesive conformingASTMC88lTypeI,II,IVandV,Grade3,ClassBandC.Adhesiveshallbeacartridge type,two-component,solidepoxybasedsystemdispensedandmixed throughastaticmixingnozzle supplied bythemanufacturer.  Acceptableinstallationandperformancetemperaturerangesshallbe verified withmanufacturer'sliteraturepriortoinstallation.

2.8 POST-INSTALLEDANCHORS

Therearetwotypesofpost-installedanchors:MechanicalandBondedanchor.

Mechanicalanchorscompriseundercutanchors,expansionanchorsandscrewanchors.Intheirusual form,undercutanchorsinterlockwith theconcreteatthebaseofthedrilledhole.Theyderive tension resistanceby bearing. Expansionanchors derivetensionresistance via  thefriction generatedby expansionforcesagainstthewallofthedrilledhole.Screw anchorsderive tensionresistanceviathe interlockofthescrewthreadswiththeconcrete.

Adhesiveanchorsareanchors inconcreteormasonrythatderivetheirresistancetoappliedtensionload byadhesionorbond.Theadhesiveforattachingbolts,rods,etc.totheconcreteisavailableinboth cartridgeandcapsule configurations.Each typeconsistsoftwoessentialparts,aresinandahardener. Inthecartridgeformat,thetwocomponentsarecontainedinseparateparalleltubesconnectedonthe endbyamanifold thatallowsthematerialsto beproportionedin theproperratioandmixedtogether. Thecartridgetoolforcesthematerialsoutofthetubes,throughthemanifold,intoandthroughamixing nozzle andintothedrilledhole.Themixingnozzle assuresthatthecomponentsarewellmixed andthe adhesiveresinisactivatedbythehardener.Withacapsuleanchor,theresinandhardenerarekept separate,butarecontainedwithinasingleglassorfoil capsule.Theentirecapsuleisinsertedintothe drilledhole.Theanchorelement,usuallyathreadedrod,istheninsertedintothepre-drilledholewitha rotationalmotionusingarotarydrill.Therotarymotionoftheanchorbreaksthecapsulecausingthe resinandhardenertomix,initiatingthechemicalreactionthathardenstheadhesive.Adhesiveanchors areavailableinavarietyofchemistries,eachwithitsownspecificcharacteristicsandcapacities.The adhesivematerialsincludeepoxies(manydifferentformulations),acrylates,vinylesters,polyesters, hybrid mortars,  and others. The specified,  installer,  and end user should become  familiar   with the requirements  of thespecific application toensuretheselected adhesive anchor andadhesive material is appropriate forthegivenapplication.

Applicable  Standard andspecifications  forpostinstalled anchor:

•    ASTM A615: Standard SpecificationforDeformed andPlain Carbon-Steel  Bars forConcrete

Reinforcement  when deformed rebarshallbeused asanchor.

•    ASTM 307,ASTM 449:Standard specificationforexternally threadedboltsandstuds.

•    ACI355.2: Qualification  ofPost-Installed  Mechanical  Anchors inConcrete

•    ACI355.4: Qualification  ofPost-Installed  Adhesive AnchorsinConcrete

•    ASTM E488: Standard TestMethods forStrength ofAnchors inConcrete Elements.

•    AC 193:Acceptance CriteriaforMechanical  Anchors inConcrete Elements.

•    AC308:Acceptance CriteriaforPost-Installed  Adhesive Anchors inConcrete Elements

2.9 CURINGCOMPOUND

CuringcompoundshallconformtoASTMC309,Type 1-DwithfugitivedyeorType2white pigmentedasapprovedbytheEngineer.

Type2whitepigmentedshallonly beusedonthesurfacesofbridgedecks,approachslabs,structural slabs,onsurfacesthatwillnotbeexposedtoview,oronsurfaceswheretheirusehasbeenapproved bytheEngineer.

 

CHAPTER3. COMMON    OPERATIONS   REQUIRED     IN    RETROFIT WORKS

The constructionprocedureforretrofittingisdifferentfromthegeneralnew buildingconstruction workin manyways.Someoftheconstruction proceduresarediscussedbelow.

3.1         PREPARATION FOR RETROFITTINGWORK:    

 

DISMANTLING     AND REMOVAL:

To facilitatetheretrofitwork,theinteriordecoration,fixtures,partitionwallsetc.adjacenttothe constructionareashallbedismantledorremoved.Appropriatemeasuresshallbetakentominimize thenoise,vibrationanddustgenerated bythework.Duringdismantlingorremovalwork,sufficient attentionshallbegivenforthesafetyissuesaswell.

TheplasterofRCCmembertoberetrofittedshall beremovedcompletelyandtheRCCsurfaceshall beexposed.Thenthesurfaceshallbechippedandroughenedcarefullytomakethesurfacereadyfor addingnewconcreteorsoon.Theepoxy bondingagentforbetterbondingofoldandnewconcrete maybe used.

Thechippingworkshallbecarriedoutcarefullytoensure thatnoexistingreinforcementisexposedor itdoesnot produceanycracksonotherpart.

Afterchipping,blowersandsuctiondevicesetc.shall beusedtoadequatelyremovechippingresidues andfinepowders.

 

3.2         POST-INSTALLED ANCHORWORK

Retrofittingworkisgenerally,carried byaddingandstrengtheningmembersofexistingstructure,so theconnectionofnewelementwithexistingstructureisofextremeimportance.Inmostofthecases theconnectioniscarriedoutbypost-installedanchorwork.Therefore,post-installedanchorshall be installed byskilledtechnicianorengineerwithenoughknowledgeofconstructiontechniques.The qualityofconnectionisalsoimportanttoensuretheperformancesoftheanchor.

Since therearetwotypesofanchoringsystemi)Mechanicalexpansionanchorandii)Chemically bondedanchor,itisstronglyrecommendedthatforretrofittingpurposechemicallybondedanchor shallbeusedtoensurebetterperformanceofworkandnolossofstrengthofexistingmember.

  1. Drilling:

Drillingshallbeatright angleto theconstructionsurface.Drillingshallbedonecarefullysothatthere isnodamagetotheexistingsteelbar.Ifsteel barishitwhiledrilling,thedrillingprocessshallbe movedto anothernearbyposition and  thepartly drilledhole shallbe appropriatelyrepaired. If possibleitissuggestedthattheexistingpositionofrebarisidentifiedbyrebardetector scannerbefore starting ofdrillingwork.

The drilling depth shall satisfy the structural provisions suggested by structural engineer  for post-installedanchor.Incontrollingthedrillingdepth,thedrillingdepthshallbemarkedtothedrill bitformakingthedesireddepth.

(ii)        CleaningHoles

Cleaningofthedrillingholeshallbecarriedoutverycarefullybyusingblowerandbrushes.Ifthere aresomedustorloosematerialsintheholetheepoxychemicalstobeusedfortheanchorworkwill notgetsufficient bondingwiththeexistingmemberhencetheperformanceof theanchorwillbe hampered.Sothiscleaningprocedureshallbecarriedoutseveraltimestoensure thatthereisnodust orloosematerialsintheholes.

(iii)       Applyingepoxybondingagent.

After cleaningthedrilledholeup to asatisfactorylevel, epoxybondingagent shallbe applied carefullytothehole.It ispreferabletousethecapsuletypebonding resin.Otherwise,theepoxy bondingagentshallbeappliedbyusinggunmachinetoensurethatadequateamountofchemicalhas beenapplied.Thisworkshall bedonebyqualifiedtechnician.Theapplication methodshallbedone accordingto theinstructionofthechemicalmanufacturer'sguideline.

iv)       Installing theanchoring barorbolt.

Theanchoringbarorboltshallbe installedslowlywithrotationwithsufficientcarebyaskilled worker.

v)         Curing

Curingshallbedoneaccordingto theinstructionofmanufacturer’s guideline.

vi)           Strengthconfirmation andinspectionofanchor work

i)Thepullouttestshallbedoneto confirmthestrengthofthepost-installedanchor.

ii)HammeringSound Inspectionshallbedonetochecktheirdegreeofadhesionandwhetherornot theseanchorsaresuitablyadhered.Ifadhesivestrengthinspectionresultsshowfailings,measures shallbetakenin accordancewithinstructionfromthesupervisororengineer-in-charge.

 

3.3         REINFORCEMENT  WORK

Reinforcementworkshallbedoneconforming"BangladeshNationalBuildingCode-BNBC"and “CodeofPracticeofPWD".

Whenrebaris usedforanchoringpurposethisshallbedonebyskilledtechnician.

3.4         CONCRETE WORK

Concretemixing,placing,vibrating,curingshallbedoneconforming"BangladeshNationalBuildingCodeBNBC"and"CodeofPracticeofPWD,"

Sincetheretrofitismadeinvariouspartsofabuildingandthesmallamountofconcreteiscastinthe retrofitwork,concreteshallbemixedinmixturemachineinaccordancewithstandardspecification andplacedcarefullytosecuretherequiredqualityofconcreteateachcasting.

Duringretrofitting,inmostofthecasesconcreteworkisdoneinnarrowplacessuchasforcolumn duringretrofitting,inmostofthecasesconcreteworkisdoneinnarrowplacessuchasforcolumn jacketing,  increasing wallthickness,  inserting shearwalletc. Soconcrete usedforretrofitting  works arerequired tohavegoodworkability aswellasgoodstrength whileitmusthaveminimal segregation and breathing.  So it  is suggested  that air entraining  water reducing  agent or high performance  air entraining water reducing agent shallbeused.Forcasting ofnarrow thicknessconcreteitissuggested tousewellgraded 12mmdowngraded  stonechips ascoarse aggregate.

Forretrofitting workthefollowing specificationforconcrete workshallbefollowed.

i)             Specified  compressive    strength  of concreteshall notbelessthandesiredstrength  of existing concretenor21N/mm2

ii)        Wellgraded stonechips shallbeusedascoarse aggregate. iii)     Minimum unitvolume ofcement shallbe270kg/m'

iv)     Maximum unitvolume ofwater shallbe185/kg/m3

v)       Maximum W/Cratioshallbe0.65

vi)        Slumpvalue shallnotbegreater than18cm.

 

3.5          NON-SHRINK  GROUT WORK

Inretrofitting  construction,  concrete shallbefirst castuptoaround 20cmbelow thebeam, andthen the remaining  portion shall be carried by non-shrink  grout work with pressure   not toleave unfilled gaps  and/or  openings.  Premix  type   non-shrink   grout  as perASTMC1107  is suggestedto use according  to themanufacture’sguideline  or instruction.  Several   brands  of non-shrink  grouts  are available. In most ofthecases thegrout ispremix type, onlycertain amountofwater isusedforgrout work. Thistypeofgroutisusedbypressurized   grout machine.

There isanoption tomixsome small size (12mm downgraded)  stone chips with  thepremix grout tomake the grout work economical.  Inthat case nopressurized  grout machine can  be used, the grout shallbepoured fromtopsidebymaking someholeintheslab. Sonon-shrink groutwork canbedone byfollowing twomethods

 

3.6         STRUCTURAL STEELWORKFORSTEELFRAMEBRACING

 

Thissectionspecifies thegeneralrequirementsforfabricationofsteelframebracingworkinthe seismicretrofitconstruction.

Typically retrofitconstructionbracingframecanbehot-rolledsectionslikeH,I,channelorpipeas designedbythestructuraldesigner.Incaseofnon-availabilityofhot-rolledsections,built-upsections (sectionsmadefromsteelplateswelding/bendingtoadesiredshape)maybeusedifpermittedbythe structuraldesignerandengineerincharge.Ineithercasebracingframeshall befabricatedinthe workshop/fabricationfactory.Importantissuesrequireattentionoftheengineerin chargeare:

3.6.1.     Welding:

  • Allweldingshallbeinaccordancewiththe standardexceptotherwisedirectedintheSpecification andtheContractDrawings.
  • Cutting,drillingandweldingonsiteisnotpermittedunlessshownondrawingsor otherwiseapproved.Suitable,safeworkingconditionsshall beensured.Weldingis prohibitedwhensurfacesare wetorwhentheambienttemperatureisbelowO degree Celsius.
  • TheContractorshalldeterminetheweldingproceduretomeettherequirementsofthe Specification, including therequirements of inspectionandQualityControl.
  • Forpre-engineeredsections,theweldingshallbecontinuousforfulllengthandonboth sides.Intermittentorpartialweldingshallnot beallowed.
  • Wherethesteelworkistobesandblastedandmetalsprayedorgalvanizedafter fabrication,cleatsandothersolidattachmentsweldedtothemembershall bewelded allroundtosealtheunprotectedsurface.
  • Welded attachmentsforfabricationorerectionpurposes shallbe subjecttothe Engineer'sapprovalandshallbeclearlyshownonthefabrication drawings.
  • Inadditiontotheabove requirements,allweldsonsteelworkshallbegroundsmooth.
  • Minimumsizeofweldsshouldbe6mmfillet.

 

3.6.4.     StorageandHandling Requirements:

  • Headedstudwhichareto befixedwith weboftheinternalsteelframebracingshallbe Storeandhandlematerialsinaccordancewiththedirectionofengineerincharge.
  • Donotstorematerialsdirectlyonground.
  • Storematerials onflat, levelsurface,raisedaboveground,withadequatesupportto prevent sagging.
  • Protectmaterialsandfinishduringstorage,handling,andinstallationtopreventdamage.
  • Maintainenvironmentalconditions(temperature,humidity,andventilation)withinlimits asdirectedbytheengineerin charge.

3.6.5.     Fixingofconnection bolts:

  • Highstrengthboltsaretightenedtoabolttensionnotlessthan70%oftheirminimum tensilestrength.Tighteningisdonewithproperlycalibrated wrenches,byturn-of-nut methodorbyuseofdirecttensionindicators(boltsorwashers). Tightenboltsm connectionsareidentifiedasslip-criticalusingDirectTensionIndicators.
  • Boltsshallnotbelessthan16mmdiameterexceptpermittedbythedesignengineer.
  • Notlessthantwoboltsaretobeusedinanyconnectionexceptpermittedbythedesign engineer.
  • BoltingupwithcloseToleranceBolts:Holesforclosetoleranceboltsshallbedrilledand reamed.  Wheretheholesarenotdrilledthroughallthicknessinoneoperation,thepartsto bejoinedtogethershallbeaccuratelylinedupwithparalleldriftsofadiameternotgreater thanthenominalsize oftheholeandnotsmallerthan0.15mmlessthanthenominal diameterandtheholesarethenreamed.  Aclosetoleranceboltshallbefittedin eachhole reamedandtightenedbeforethenextholeis reamed.  All boltsshallbere-tightenedafter thelast bolthasbeen fitted.
  • Correctingholealignments:Driftingtoalign holesshall notenlargetheholesordistortthe metal.   Holeswhichcannotbealignedwithoutdistortionshallbeacauseforrejection unlessenlargementbyreamingis specificallyapprovedbytheEngineer.

3.6.6.     Surfacecoatings(paint):

  • Atleastonecoatredoxideorequivalentprimershallbeappliedtothefabricatedsteel membersatworkshop.
  • Steelworkshallbedryandcleaned.
  • Steelsurfacestobeembeddedinconcreteshallbeleftunpaintedandneednotbeblast cleaned.Thepaintedsurfaceshall continue80mmbelowtheconcretesurface.
  • Wheresteelworkistobeprotected againstcorrosionwithapaintcoatingsystem,itshallbe inaccordancewithBSENISO12944andtheProjectDocumentation.
  • Additional stripe coats of primer or undercoat shall be applied in the
    •  
  • Weldedsurfaceswhereaweld-throughprimerhasbeenused
  • Steelworkwhichwillbeexposedexternally inthefinished works
  • Alledges,comersandboltholes
  • Sealgapsbetweenadjacentcomponentssuchasshopandsiteboltedconnections.
  • Workshall notprecedewhenthesteelsurfacesarewetortheambienttemperature,ordew pointis not withintherangerecommendedbythe paintmanufacturer.
  • Painting sitefixedbolts andwelding

 

•  Allprotruding portionsofbolt assembliesandsiteweld surfacesshallbecleaned to removetracesofoil,dust,weldingfluxetc.

•  Thepaintsystemshallbecompatible withthesurfacetreatment systembeingusedon thesurrounding surfaces.

•  Bolt assemblies which are supplied with protective treatment need not be paintedexceptwhererequiredbytheEngineer's architectural  drawings

 

3.6.7.     NotesforErection

  • TheEngineer shallbenotifiedinwritingofthestartingdatepriortothecommencement offieldoperations.
  • Components shallbelifted,placed, andmaintained inposition usingappropriate lifting equipment, temporary bracing, guys,orstiffening devices sothatthecomponents areat notimeoverloaded, unstable,orunsafe.Additional permanentmaterialmaybeprovided, if approvedbytheEngineer,toensurethatthemembercapacitiesarenotexceededduring erection.
  • Fortemporary fitups,maingirdersplicesandconnections shallbealignedwithdriftpins andasufficientnumberoffittingupboltsshallbeinstalledtomaintaintheintegrityofthe connection.
  • Repairs to erected material will onlybe permitted after therepair procedure hasbeen approvedbytheEngineer.
  • Fillingofmisplaced holesbyweldingispermitted onlywiththewrittenapproval oftheEngineer.
  • Hammering thatwilldamageordistortthemembersisnotpermitted.

 

3.6.8.     Responsibility ofthefabrication Contractor:

 

  • The contractorhas to review the design drawingsand make comments,so that necessary andifthestructural designprovision permits,contractorcanchangethelength ofsomeofthemembers toensure thattheirweight isgoingtobelightenough forthe erection method the contractor isplanning to use orthe connection type that isthe contractorconversewith.
  •  

 

  • If drawing istheresponsibility of thecontractor,the drawingsshallbe submittedtotheengineerinchargeforapprovalbeforeactualfabricationwork.

CHAPTER 4: RETROFITTING METHODS:

Retrofittingworkisgenerallycarriedoutbyaddingandstrengtheningmembersofexistingstructure toimproveitsstructuralperformancesagainstearthquakeorotherloads.Therearemanymethods to makethisstrengtheningworkswhicharetermedasRetrofittingMethods.

Thefollowingpicturesandtablesshowdifferenttypesof RetrofittingMethods.Thesemethodsare appliedtothestructuretoimprovethe structuralperformancesofthebuildingsuchas strength, ductility,structuralbalanceetc.

Followingsectionswillcovertheconstructionprocedureofdifferentretrofittingmethods,whichare verycommonandusefulforBangladesh.Theseretrofittingmethodswillimprovethe structural performanceofthebuildingbutthemethodsmustbecompatiblewiththeexistingstructure.So the methodstobeappliedinbuilding mustbeselectedbyqualifiedstructural engineerwith detail assessmentandretrofitdesign.