REVIEW OF PROGRESSIVE COLLAPSE ANALYSIS OF REINFORCED CONCRETE STRUCTURES WITH FLAT
SLAB CONSIDERING EFFECTS OF GEOMETRICAL (HORIZONTAL and VERTICAL) IRREGULARITIES.
Shantnoo S. Girme1, Dr. Atul B. Pujari22
1
Abstract This review paper presents Progressive Collapse analysis(PCA) of Reinforced Concrete Structures with Flat slab considering effects of geometrical (horizontal & vertical) Irregularities. Progressive collapse failure starts with local damage and extend up to whole structure. Flat slab buildings are more prone to progressive collapse than moment frame buildings, its behavior to resist progressive collapse must be examined, Since absence of beams to redistribute load due to get more effect after removing columns. to get more Clair idea about PCA purpose in review Some paper considered various model having geometrical irregularity by conducting Linear static progressive collapse analysis and dynamic PCA as per GSA guidelines (2016). mostly research papers explores the different locations for column removalsituationineach model at ground storey and the results are analyzed for each case in terms of demand capacity ratio (DCR) at critical sections, vertical joint displacement and chord rotation at column removal locations and thus sensitivity of building to progressive collapse is calculated accordance with relevant acceptance criteria consignedinDOD guidelines (2009). Along with that in this review paper cover effects of geometrical irregularities as well flat slab effects in RCC structure.
Key Words: Progressive collapse, flat slab, vertical displacement, DCR, Chord rotation, GSA, DOD, local damage, static linear analysis,dynamicanalysis,seismic forces, ETABS
1.INTRODUCTION
Thecollapseofloadcarryingstructuralelementmayleadto progressivecollapseasapartorwholestructure.According toGSA2016guidelines,progressivecollapseisdefined as extentofdamageorcollapsethatisdisproportionatetothe magnitudeoftheinitiatingevent.Theprogressivecollapse initiates, when one or more load carrying members are removed.Whenoneormoreloadcarryingelementsremove chainreactionoffailuresstructurestart.Theguidelinesof the GSA and DoD suggested the Alternate Path Method (APM) for progressive collapse analysis where a single columninthegroundlevelisassumedtobeunexpectedly missingandanalysesarecarriedouttoassesstheabilityof theweakenedstructuretopassthroughthemissingcolumn. The alternate load path method (APM) focuses on the
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verticaldeflectionofthebuildingafterthecolumnhasbeen suddenly removed. The collapsing structure seeks for alternativeloadpathcontinuouslyforpreventprogressive attentioncollapseandsurvive.Traditionaldesignworknot considered extreme loading conditions. Previously some experiences grab of structural engineer’s attention Ronan pointapartmentbuilding,Alfred.P.Murrahbuilding,skyline plaza, world trade Centre. Based on the type of collapse occur, progressive collapse divided into pancake type, zipper type,domino type,section type,instability typeand mixedtypecollapse.Thepurposeofthisstudyistoanalyze the effect of geometrical irregular RC flat slabs for progressivecollapse.progressivecollapseanalysiswherea single column in the ground level is assumed to be unexpectedlymissingandanalysesarecarriedouttoassess the ability of the weakened structure to pass through the missing column. PCA is classified as PRESSURE LOAD Internal gas explosion, Blast load, Extreme wind pressure and another type is IMPACT LOAD Aircraft impact, Vehicular collision, Earthquake in this study analyses behaviorofbuildingundercolumnlossatgroundfloor.
1.2 OBJECTIVE OF WORK
2. LITERATURE REVIEW
Sivq naveen, Nimmy Mariam Abraham, anitha kumari.,[3] they analyzed irregular structure under earthquakeloadsandtheresultsofstructuralresponsein theformofstorydisplacement,storydrift,baseshearand overturning moment. And for validation response is comparedwithregularbuilding.Inthispapertheynotonly study single irregularity but also combinations taken in design. In vertical irregularities mass, stiffness, and geometrical vertical irregularities and for horizontal torsional,re enteredcornersconsidered.total54irregular frames are analyzed out of witch 34 configuration have
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Post graduate student of K J college of engineering and management research, pune Maharashtra, india
Associate Professor Department of civil engineering, KJ College of Engineering & Management research, pune 411048, India.
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single irregularity and 20 have combine and finally they studycriticalcombinationofirregularity.Andresultisthe combination of stiffness and vertical geometrical irregularities has given maximum displacement response where’sthecombinationofre enteredcornersandvertical geometrical irregularities has shown less displacement response.
o Ravindra nagar, Vinay Agrawal, Suyash Garge., [4] studiedtheeffectsofprogressivecollapseofRCflatslab building 8 floor by static analysis with or without peripherybeamlayoutasperGSA2016guidelinesand resultisanalyzedintermofjointverticaldisplacement, chordrotationatcolumnremovallocations.Andresult showed incorporation of perimeter beams in flat slab building improved PC resistance and reduces joint displacements, chord rotation at column removal locationsbyprovidingsufficientstiffnessandloadpath. Andresultisgetthatmorepronetoprogressivecollapse incaseofcornercolumnremovalthananyothercolumn removal conditions. for interior column removal locations addition of external periphery beam not resultedgoodresistancethananotherlocationscolumn removalresultsget.Alsotoenhanceprogressivecollapse potential retrofitting tools along withpartial beams in framelayoutisgrateoptionasperthisstudy.
o Zabihullah, Priyanka singh, Mohammad zamir.,[5] studiedseismicresponseofRCstructuresofG+7story havingverticalandhorizontalirregularitiesanalyzedand comparedbyusingresponsespeculummethodasperIS codes.Thecomparisonofthismodelsarecarriedoutby base shear, fundamental period, storystiffness, lateral displacement, story drift, eccentricity, torsional irregularity. Out of the building models horizontal irregular model ismost susceptible duringconsidered earthquake. They discussed most imp seismic parameters of all the models to get idea of irregular building performance. Idea is get Clair that the more asymmetrical the building more will be its lateral displacementandstorydisplacementandstorydrift.The more asymmetrical building, more will eccentricity as wellastorsionalirregularities.
o Suyash Garg, Vinay Agarwal, Ravindra nagar., [6] in thispaperprogressivecollapsebehavioroffivestoryRC flatslabbuildingisassessedbyremovingcolumnfrom firststoryanddynamicanalysisisconductedasperGSA guidelines.Inthispapersustainablypointofviewalso touches means the construction of new houses, often requiredformofenergyandcreatesharmfulgases,the CO2emissionfactorsrateis236.8kgco2/cubicmeterfor M25 concrete and 424.2kg CO2 /ton for Fe500 rebar. Therefore, author considered money of protect the environmentalsoconsidered.resultisanalyzedinterm ofjointverticaldisplacement,chordrotationatcolumn
Factor value:
removallocationsinthreecasesatcolumnremovalfirst story,edgeandcornercolumnremoval.
o P. olmati, J. sagseta, D.cormie, A.E.K. jones.,[7] .This paperpresentsaframeworkforasimplifiedreliability analysisandderivationofsafetyfactorsforcomputing theprobabilityofpunchingofflatslabconcretebuildings subjected toaccidental loads such as column removal, slabfallingfromaboveorblastload.approachinstudyis proposedtotakeintoaccountuncertaintyinthegravity load in the slab. Thisstudy is done by usingadvanced dynamicsoftware’sandgetideasthatTheresponseof the slab in the blast load scenario is more impulsive compared to the column removal and falling slab scenarios,althoughtheslabrotationoutsidethecolumn atfailureisofsimilarmagnitude.And,thevariabilityin thegravityloadsintheslabinfluencestheinertialeffects and demand capacity ratio of the slab column connectionsafterextremeevents.Theuncertaintyinthe loadappliedintheslabwasfoundtohavealesscritical role inthe fallingslabandblastload casesconsidered duetothehighsheardemandcomparedtothecolumn removalscenario.
o Suyash Garg, Vinay Agrawal, Ravindra Nagar[8] this studyfocusesonbuildingstrengthenedbyusingshear wall,perimeterbeamanddidPCAbyremovingcorner column, interior column, edge column and results comparedwithstaticanddynamicanalysismethodsit containscolumnremovealternatively,simultaneously, sequentiallybyusingGSAandDODguidelines.
o Suyash Garg, Vinay Agrawal, Ravindra Nagar[9] this paper gives improved PCA results of RCC flat slab building under different corner column failures analytical research examines for failure criteria and improvement in the progressive collapse resistance usingstaticanalysisoffiveandten storeyirregularR.C flat slab building by incorporating perimeter beams along with strengthened perimeter columns in the building.Theprogressivecollapsestudyisconductedby removingdifferentcornercolumnsonthegroundfloor aspertheGSAguidelines
o D. z. yankelevsky, Y.s.karinski, V.r.feldgun[10] this studyfocusonthenumerical detailedsimulationsofa connection under impact conditions and study of dynamic response of RC connection between slab and columnduetofallingofupperslab.Andpointscoverin studieslikeshearreinforcement,reinforcedductilityon connectionsandtypeoffailures.Entireanalysisdoneby FEMinANSYSAUTODYNcommercialsoftware.Inthis work they used fine mesh of three dimensional solid elementsusedinconcreteslabdomain.
Flat slab fails in punching issue between rebar and surroundingconcretehasincludedtopandbottommeshes withrebar’sinbothdirections.Andforcolumnstrengthening
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longitudinal rebar’s and stirrups in connection structural system.Andthisshortdurationresponseslipduringbond actionbetweenarebarandsolidintactconcreteisignored andtherebar’sidealperfectbondconnectiontotheconcrete.
o Silpag, Yaminisreevalli.,[11] Thispaperdiscussesthe existing researchers on the analytical study, experimental study, and numerical simulations of flat slab structures along with various load resisting mechanisms to mitigate progressive collapse. Further, various strengthening techniques available in the literaturefortheflatslabstructureshavebeendiscussed.
o Justin M Russell , John S Owen and Iman Hajirasouliha ., [12] In this study, finite element analysisisusedtoreplicatecolumnlossscenariosona rangeofreinforcedconcreteflatslabfloormodels.The model was validated against the results of scaled slab experimentsandthenusedtoinvestigatetheinfluenceof differentgeometricandmaterialvariables.Andbasically result get that is the most critical removal location dependsontheslabgeometrywithaninternalcolumn removalcasecausingthelargestnonlinearbehaviorfor stiffer slabs and a corner column removal for more flexible slabs. In addition, the use of low strength concreteresultsinstructuresmorepronetoprogressive collapse,evenafteraccountingforanincreaseinflexural reinforcement.
o S. M. Marjanishvili, P.E., M. ASCE.,[13] in this study detailed information or guidelines about to protect existingandnewbuildingfromPCAbyDODandGSAis givesafterworldtradecentercollapse. Bylinear elastic static; nonlinear static; linear elastic dynamic; and nonlinear dynamic. they discuss the advantages and disadvantages of each method. And conclude that the most effective analysis procedure for progressive collapseevaluationincorporatestheadvantageousparts of all four procedures by systematically applying increasingly comprehensive analysis procedures to confirm that the possibility of progressive collapse is high.
o Dario Coronelli a, Marco Lamperti Tornaghi b, Luca Martinelli a, Francisco Javier Molina b, Aurelio Muttoni….etc and all.,[14] this group of people did experimental work on full scale flat slab building for gravity and lateral loads undertaken in Slab STRESS researchprojectcarriedbyELSAlaboratoryofEuropean commissionjointresearchCentre.Theyconsideredtwo different longitudinal reinforcements. Work is done basicallyfocusingontwothingsthatisprimarywalland flatslabs.Variesdevicesareusedtomeasureinclination ofcolumnandcyclicloadingtests.
o Saeed Sarvari, M. Reza Esfahani.,[15] they did experimental work on post punching behavior of flat slabmeanschangesindimeterofreinforcement,changes
inshearreinforcementpatterninflatslab,example truss type, sometime providedadditional bent up bars than required, around column slab connection polar or crossoverarrangementofsteelandsoon17slabwith cover variations. The effects of integrity, compressive, shear, truss, and bent up reinforcements, diameter of tensile reinforcement, and concrete cover of tensile reinforcement on the post punching behavior of slab column connections were studied. The results of the experiments indicate that the integrity reinforcement significantlyimprovesthepost punchingstrength.The increase of the concrete cover of the tensile reinforcementanddecreaseofthediameterofthetensile reinforcementresultinanincreaseofthepost punching strength.
o Rasha T.S. Mabrouk , Amr Bakr, Hany Abdalla.,[16] their ongoing research seven half scale specimens are cast and tested to know Effect of flexural and shear reinforcement on the punching behavior of reinforced concreteflatslab.Theyconsideredparametersspacing betweenverticalstirrups,widthofthestirrups,number of stirrups branches and the ratio of the horizontal flexuralreinforcement.Duringtesting,ultimatecapacity, steel strain, cracking pattern and deformation were recorded.Theexperimentalresultswereanalyzedand compared against values estimated from different internationaldesigncodes.
o Szczepanwolinski.,[17] thisarticlenameisRobustness andvulnerabilityofflatslabstructure.Inthispaperthe importanceofassessingboththestructuralrobustness and vulnerability of flat slab structure to catastrophic andunforeseeneventsishighlightedandanalyzedand the risk is evaluated. The vague nature of possible hazards and their consequences, semi quantitative approaches to risk eliminated by fuzzy numbers has beenused.
o J.M. Russella, J.S. Owenb , I. Hajirasoulihac ., [18] Has analyzedThenonlineardynamicresponseofastructure afterdynamiccolumnlosseventisconsidered,including the redistribution of loads and displacement profile. These results are then compared to equivalent static casesinordertodeterminetheDynamicAmplification Factor (DAF). For the range of structures, they considered,theDAFwascalculatedasbetween1.39and 1.62 for displacements, with lower factors associated with a higher nonlinear response or slower column removal. Additionally, the shear forces in remaining columns may exceed 200% of their fully supported condition,withadifferentassociatedDAF.Theeffectsof increasingthe tensile strength ofconcrete due to high strainratesarealsoconsidered.Theydidexperimenton FE displacements results against time with different removal times compared to the experimental results. Fourdifferenttimes(0,20,50and100MS)areusedto reduce the reaction force provided by the temporary
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support.InthisworkstudyisappliedexperimentallyThe dynamic response of RC flat slab structures after a column loss demonstrates that a sudden removal can considerably increase the peak displacements and the shearforcescomparedtothestaticcondition.TheDAF for displacement values is related to the extent of damageandnonlinearitywithintheforcedisplacement response.
o Kai Qiana , Yun Hao Wengb , Bing Lic., [19] Has analyzed impact of two columns missing on dynamic responseofRCflatslabstructure.Thesetwospecimens haveidenticaldimensionsandreinforcementdetails.One ofthesubstructuressufferedalossofaninteriorcolumn scenario while another one was subjected to a two columnsoneinteriorandotherisedgecolumnmissing.It is found that although both specimens had exceeded their yield load capacity, no collapse occurred as considerablecompressivemembraneactiondeveloped in the RC slab to help redistribute the loads. With the droppanels,nopunchingshearfailurewasobservedin the slab column connections after removal of the column.Thenumericalresultsindicatedthatmissinga singleinteriorcolumnachieveslargerdynamicresponse than that of the loss of a single corner or an exterior column. And for missing two column scenarios, the substructuresunderthelossofbothacornercolumnand an adjacent exterior column simultaneously may experience more severe damage than that of the substructures subjected to the combined loss of an interiorcolumnandanadjacentexteriorcolumn.
o Colin gurley.,[20] gives information and differences betweenprogressivecollapseandearthquakeresistance. Basically earthquake engineering focuses on sway mechanisminwhichbuildingasawholemovesideways andmaycollectunderitsownweightandexplosionmay removes one or several load bearing column, walls or transferstructureloadingtoverticalcollapseanddouble spanmechanism.
o Khaja ateequddin, waseemsohail.,[21] hasanalyzed Effects of irregularity shape on flat slap multistory building under lateral loading using etabs. Horizontal andverticalirregularmodelsareanalyzedbyusingetab softwareandresultsplottedagainstwindloadaswell earthquakeloads.Andfinelygivescomparisonbetween storyshear,drift,displacement.Timeandallproperties behaviorwithmodel.
o NiramjanChaudhary,nitinverma.,[22] theydidwork on seismic behavior of flat slab multistory building in plan irregularities considering T, U, PLUS shape G+13 floorbyusingE tabssoftwareconsideringcolumnhead, drop panels with and without both. nonlinear time history methodusedto getdifferent parameters story displacement, story drift, base shear, time period by usingiscodes.
3. CONCLUSIONS
The joint displacement and Chord rotation at column removal locations are evaluated when different locations of column on each building removes the findingindicatesthestudiedflatslabismorevulnerable incaseofcornerColumnremovethanedgecolumns. ď‚·
Joint Displacement and Chord Rotation values are inversely proportional to progressive collapse resistance as chord rotation decreases, Progressive CollapseResistanceincreases. ď‚·
The Irregular Structure also sustains progressive collapseeffectafterremovalofcolumnsAlternately,and theeffectofflatslabonPCAisveryinfluentialbecause theexistenceofflatslabafterremovalofcolumndoes not experience overall collapse, but some structural elements collapse. Load distribution after removal of columnthroughnearbycriticalcolumnisdone,Column DCR<1.5forirregularandDCR<2FORregularstructure. giveslimitofsafetymember. ď‚·
The result values of vertical joint displacement and chord rotation and DCR is taken as per GSA load combination.buildingisdesignedforseismicallyforces hence seismically designed building columns have inherentabilitytoresistprogressivecollapse. ď‚·
ThepurelyRCregularflatslabstructuralsystemisless vulnerablethanirregularflatslabstructurebecausethe ductilityofthesestructuralsystemisgenerallylimited bythedeformationcapacityofslabcolumnconnection. i.e., penetration force in the slab at the connections, which should retain its load bearing capacity when column removes adjacent column get additional load andthisisrelatedwithmaximumdisplacementandDCR arelessthan2aswellchordrotationislessthan0.05in allcasesthereforeadjacentallmembersaresafe. ď‚·
DCR values for column adjacent to removal column maximumwhencentralInternalcolumnremoves,then another Internal column, edge column of longer side, then edge column on shorter side, and finely corner column.
ď‚·
As the structural response depends on degree of irregularity,type,locationthosefactorneedtobetaken carewhiledesigninganystructure.Thiswouldhelpin incorporating irregularities in structures without compromisingtheirperformance.
ď‚·
MostlyFlatslabonthegroundfloorofabuildingwhen the critical column and inner sides of a building are removedcollapsedbutdoesnotaffectthefloorabove, becausetheloadontheupperfloormovestoaflatslab systemonthegroundfloorofthebuilding.Theirregular
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buildingstructuredidnotcollapseaftertheremovalof thecolumn.
ď‚·
Ingeneral,ifthestructures aredesignedanddetailed withanadequatelevel ofcontinuity,redundancy,and ductility can develop alternative load paths which in return preventstheloss of anindividual memberand preventprogressivecollapse.
REFERENCES
[1] GSA,DesignguidelinesfornewfederalOfficebuilding andmajormodernizationprojects,ProgressiveCollapse Analysis,TheUSgeneralserviceadministration,2016.
[2] UFC, Unified Facilities Criteria (UFC), Design of building to resist progressive collapse. The USA DepartmentOfDefense.
[3] Sivq naveen, Nimmy Mariam Abraham, anitha kumara.,(2018)“Analysisof irregularstructureunder earthquack loads” Ravindra nagar, Vinay Agrawal, SuyashGarge.,(2020)“progressivecollapsebehaviorof reinforcedconcreteflatslabbuildingsubjecttocolumn failureindifferentstorys”
[4] suyashGarg,VinayAgarwal,Ravindranagar.,(2020) “PCAbehaviourofreinforcedconcreteflatslabbuilding subjecttocolumnfailureindifferentstoreys”
[5] Zabihullah,Priyankasingh,Mohammadzamir.,(2020) “Effects of (vertical and horizontal) geometrical irregularitiesonseismicresponseofrcstructures”
[6] suyashGarg,VinayAgarwal,Ravindranagar.,(2021)“ Sustainability assessment of methods to prevent progressivecollapseofrcflatslabbuilding”
[7] P. olmati, J. sagseta, D.cormie, A.E.K. jones., (2016) “Simplifiedrealibilityanalysisofpunchinginreinforced concreteflatslabbuildingunderaccidentalactions”
[8] Suyash Garg, Vinay Agrawal and Ravindra Nagar...[2020]“casestudyonstrengtheningmethodsfor progressivecollapseresistanceofRCflatslabbuilding
[9] Suyash Garg, Vinay Agrawal and Ravindra Nagar,,[2020] “Improved progressive collapse resistance of irregular reinforced concrete flat slab buildingsunderdifferentcornercolumnfailures”
[10] D. z. yankelevsky, Y.s.karinski, V.r.feldgun., (2020) “Dynamicpunchingshearfailureofrcflatslabcolumn connectionundercollapseslabimpact”
[11] Silpa g, Yamini sreevalli., (2020) “A review of progressive collapse of reinforced concrete flat slab structure”
[12] JustinMRussell,JohnSOwenandImanHajirasouliha .,(2018)“Nonlinearbehaviorofreinforcedconcreteflat slabafteracolumnlossevent”
[13] S.M.Marjanishvili,P.E.,M.ASCE.,(2013)“Progresive analysisprocedureforprogressivecollapse”
[14] Dario Coronelli a, Marco Lamperti Tornaghi b, Luca Martinelli a, Francisco Javier Molina b, Aurelio Muttoni….etcandall.,(2021)“testingof full scaleflat slabbuildingforgravityandlateralloads”
[15] Saeed Sarvari, M. Reza Esfahani.,(2020) “an experimentalstudyonpostpunchingbehaviorofflats
[16] RashaT.S.Mabrouk, AmrBakr,HanyAbdalla.,(2017) “ Effect of flexural and shear reinforcement on the punchingbehaviorofreinforcedconcreteflatslab.
[17] Szczepan wolinski., (2017) “Robustness and vulnerabilityofflatslabstructuresNiramjanChaudhary, nitin verma., (2020) “Seismic behavior of flat slabs in multistorybuildings.
[18] J.M.Russella,J.S.Owenb,I..,(2019)“dynamiccolumn lossanalysisofreinforcedconcreteflatslab.
[19] KaiQiana,Yun HaoWengb,BingLic.,(2018)“impact oftwo columnmissingondynamic responseof rc flat slabstructures”
[20] Colingurley.,(2008)differencesbetweenprogressive collapseandearthquakeresistance.
[21] Khaja ateequddin, waseemsohail.,(2019) analysis Effects of irregularity shape on flat slap multistory buildingunderlateralloadingusingetabs.
[22] NiranjanChaudharyandnitinverma..[2020] Seismic behaviorofflatslabinmultistoreybuildings
[23] UsersguideETABS2016,Integratedbuildingdesign software.Computersandstructuresinc,Berkely2016
[24] Is 456:2000, plain and reinforced concrete code of practice,bueroofIndianStanders,newdelhi2000
BIOGRAPHIES
Shantnoo Shamkant girme is a PG student of structural Engineering at civil engineering department, KJs Educational Institute,kjcollegeofEngineering andmanagementresearch,pune 1’st Author
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DR Atul B. Pujari is working as Associate Professor in civil engineering Department, KJs EducationalInstitute,kjcollegeof Engineering and management research,pune,Maharashtra 2
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