Comparative Study of Waffle Slab and Conventional Slabs with Bracing System Using Time History Analy

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 09 Issue: 08 | Aug 2022 www.irjet.net p-ISSN: 2395-0072

Comparative Study of Waffle Slab and Conventional Slabs with Bracing System Using Time History Analysis

1(M.Tech. Structural Eng.), Civil Engineering Department, Institute of Engineering and Technology, Lucknow 2Assistant Professor, Civil Engineering Department, Institute of Engineering and Technology, Lucknow ***

Abstract - An Earthquake ground motions are greatly influenced by the analysis and design of structure. Analysis of the structure with various slab arrangements, such as standard slabs, grid/waffle slabs, and braced structures, isthe goal of this work. Traditional slab designs are typically not chosen for large span structures, but waffle slab and ribbed slab are the most appropriate and cost-effective options. However, these slabs have recently seen significant growth as these are lighter, durable and shows minimal signs of visible damage due to presence of waffle pod in the slabs. The bracing system allows load to be transmitted from the frame to the braces, increasing the structure's capacity to withstand lateral loads. Using ETABS software, time history analysis is performed in order to study the seismic stresses' effects on structures with different slab layouts. Storey drift, base shear, and storey displacement are among the parameters thathave an impact on a structure's performance and are vital in determining how building will respond under seismic loads and other load combinations. IS 456-2000 code is taken into consideration for designing purpose. Live loads are taken in accordance to IS 875-part 1 and earthquake analysis is performed according to IS 1893-2016 Part 1

1. INTRODUCTION

ThisAnearthquakeisstrongshakingoftheearthresulting fromtheenergyreleasedbytectonicplatemovement.Often, earthquakesresultinseveredamagetolifeandproperty[1] An expanding quantity of research has been conducted in this area due to the growing interest in designing earthquake-resistant constructions or buildings [2]. It is critical to ensure that the structure is capable of withstanding horizontal ground vibrations. RCC slab structure is an important part of the building that is designedtobearbothverticalandhorizontalloadsduring earthquakes. While, conventional slab is one that is supportedbystandardbeamsandcolumns.Inatypicalslab, theloadisdistributedfromtheslabtothebeam,thebeamto the column, and the column to the foundation. [3]. On the otherhand,wafflesaremadetocoverlargespanwithleast possible & have been widely used nowadays in both residentialandcommercialstructuressuchasauditoriums, airports,theatrehalls,andshowrooms,roofingetc.where

value:

thereisminimalornoneedforcolumns.Theseverityofthe quakes and the qualities of the structure determine a structure's strength and stability during an earthquake. Bracingisaneconomicalandefficientwaytostrengthenthe framestructuresagainstlateralloads.Thesteelbracesare usuallyplacedinverticallyalignedspaces.[4]Steelbracing are cost-effective, easy to install, takes up less area and providetheextrastrengthandstiffness.Bracedframesare highly effective for structures subjected to severe lateral loads,suchasearthquakeloads.Timehistoryanalysisisan adaptivemethodforevaluatingseismicbehaviourofmultistoreybuildingfortherangeofseismicintensitiesinorder to understand how parameters such as storey shear , displacement, storey stiffness etc. affects seismic performance[5].Theprimarygoalofthestudyistoevaluate thestructuralbehaviourusingwaffleslabandconventional slab with X- type bracing in seismic zone IV in type II(medium)soil.

2. Literature Review:

Kaushal Vijay Rathod, Sumit Gupta[2020]: Thisresearch paper discusses the outcomes of a time history study performed on a ten-story building. There is a necessity to study seismic analysis in order to develop earthquake resistance structures in order to assure safety against seismicforcesofmulti-storybuildings.Thisseminarreport usesETABStodoanonlineartimehistoryanalysisonatenstory RCC building frame while taking into account the timingofthe1940ElCentroEarthquake[6]

Theworkby Dhanaraj M. Patil , Keshav K. Sangle [2015]: Theseismicresponsecharacteristicsofvariousstructures with distinct bracing methods are evaluated in order to evaluateseismicbehaviourofeachsystem.

Manoj Kumar M, Victor Samson Raj A,et al [2020]: A structure'sductilityandenergydissipationcapabilityplaya keyroleinitsabilitytowithstandseismicforce.Bracingwas utilized to increase a steel-framed structure's ability to dissipateenergy.Here,asteel-framedG+14storybuilding was chosen for examination. The addition of the X, V, and zipper bracing increased the ability of these structures to dissipateenergy.Fortheanalyticalanalysis,STAADPROand SAP2000areused. Pushoveranalysisisusedtorelate the performanceofthevariousbracedframedstructures.Forall steel frames, the positioning of the bracings on the edge

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 09 Issue: 08 | Aug 2022 www.irjet.net p-ISSN: 2395-0072

structurehasraisedthebaseshearconveyinglimit,raised theperformancepoint,anddecreasedthedisplacementof theroof.

As per previous study by Mirza Mahaboob Baig, , Abdul Rashid , Y Pavan Sai Durga Reddy et.al 2020: Thepurpose of their study is to determine behaviour of waffle slab constructions when the obstructing columns have been removed from the building’s hall and room. This study concludes that ribbed/waffle slab structures are more susceptibletolateralloadsthanconventionalslabstructures because of an increase in self-weight. The research was carriedoutinseismiczoneIIIanditwasfoundthat,inhigh seismic zones, ribbed slab structures perform less than conventional slab buildings because they have fewer columns, but that performance can be improved by structuralretrofitting[4].

Sawwalakhe, A. K., & Pachpor, P. D. (2021): Thestudy's goalistodeterminewhichoftheregularslab,flatslabwith drop, and grid floor is the most economical. For a G+5 commercial multi-story structure with a flat slab, a conventionalslab,andagirdslab,variablessuchasstorey displacement, shear force, bending moment, and storeys drift were examined in this work. The total number of structures studied for this purpose is 18. All structures in India's seismic zone III have had their performance and behaviourexaminedusingdeadload,liveload,andseismic load.[7].

2.1. Research Significance:

1. To compare the performance-based analysis of conventional slab and waffle slab in commercial buildingofseismiczoneIV.

2. Toperform timehistoryanalysisonconventional slabandwaffleslab.

3. Tostudyandcomparetheseismicparameterssuch as storey drift, storey shear, displacement, and storeystiffness,jointdisplacementetc.

3. Methodology:

This paper includes modelling G+4 building by creating a planofdimension45m*45mwithstoreyheightof5meach. Defining & assigning properties of materials, RC frame section properties and load condition, using ETABSv16 software. Then we define time history function taking Chamoliearthquakedataasreferencefortheanalysis&the studyisperformedonseismiczoneIV

3.1 Modelling Parameters:

Table

1: Building parameter

Areaofthebuilding 45*45m2

Heightofthebuilding 25m Columns

C1 450*450mm2

C2 450*350mm2 C3 450*600mm2

Beams B1 350*400mm2 B2 350*500mm2

SlabType Waffleslab

Slabthickness 90mm Spacingofribs 1500mm Widthofribs 200mm Overalldepth 800mm Bracings X-type(ISA200*200*15)

Table 2: - Material properties:

3.2 Loading Conditions:

Fig1. Loading Properties

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 09 Issue: 08 | Aug 2022 www.irjet.net p-ISSN: 2395-0072

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 09 Issue: 08 | Aug 2022 www.irjet.net p-ISSN: 2395-0072

4. Results and Discussion:

AsaresultofcomparisonbetweenthebracedandnonbracedG+4structure,followinginferenceshasbeenmade:

4.1 Joint Displacement:

Themaximumjointdisplacementat23.24sec.isfoundto be492.455mminconventionalslab.Similarly,themaxvalue of joint displacement for waffle slab is found to be 263.666mmat5.02sec.Thevalueforwaffleslabisobserved tobe47%lessthanthatofconventionalslab.

Chart 3: Storey Drift

4.3:

Storey Stiffness:

Storeystiffnessisamoreforconventionalslabstructure incomparisontowaffleslabstructure.Thevaluegradually increasesmovingfrombottomtotopstoreyreachespeakand fallsuddenly.Themaximumvaluesobtainedforconventional slab and waffle slab are 668862.633 kN/m & 657529.69 kN/m.

Chart 1: Displacement due to Conventional Slab

Chart 2: Displacement due to Waffle Slab

4.2 Storey Drift:

AsperIS1893(part1): 2002 CI. 7.11. 3,thestoreydrift limitis0.004timesthestoreyheight[8].andaccordingtothe graphsobtainedmaximumdriftis0.001655onwaffleslab and .0010588 on conventional slab which is within the permissiblelimits.

Chart 4: Storey Stiffness

4.4 Storey Displacement: Storey displacement is maximumatthetopstorey(27.361mm)forconventionalslab andminimumatthestructure’sbase.Whileforwaffleslab the maximum displacement is (24.26mm). Max value of storeydisplacementforwaffleslabisapprox.16%lessthan themaximumvalueofdisplacementintheother.

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 09 Issue: 08 | Aug 2022 www.irjet.net p-ISSN: 2395-0072

Materials Today: Proceedings,Jan.2020,vol.33,pp.700–704. doi:10.1016/j.matpr.2020.05.823.

[2] V. P. Thakkar, A. K. Chandiwala, and U. D. Bhagat, “Comparative Study of Seismic Behavior of Flat Slab and Conventional RC Framed Structure.” [Online]. Available: www.ijert.org

[3] “COMPARATIVE STUDY OF THE SEISMIC PERFORMANCEOFRCCBUILDINGWITHRIBBEDSLABAND GRIDSLAB140.”

Chart 5: Displacement of buildings

5. Conclusions:

Comparativestudyofwaffleslabandconventionalslab bothhavingbracingsystemusingtimehistoryanalysisshows that waffle slab has approx 12% less displacement than conventional slab i.e, waffle slab performs better when it comestolateraljointdisplacementofjointlabel1,Storey5. While the maximum values of storey drift conclude that waffle slab shows lower drift i.e. approx. 57% lower than conventionalslabstoreydriftvalues.Anystorey'sstoreydrift induced by the required minimum designed lateral force, withapartialloadfactorof1.0,maynotbelargerthan0.004 timesthestoreyheight,perIS1893Part1:2002Cl.7.11.3. The plots show a maximum drift of 0.02, which is within acceptable bounds. Moreover, conventional slab shows slightlylesserStoreystiffnessascomparedtowaffleslab[9] However, storey displacement values conclude that conventional slab displaces 11% more than waffle slab. Hence, this can be concluded from the results that conventionalslablagsbehindinsomeaspectssuchasstorey displacementanddriftincomparisontowaffleslabi.e,waffle slabperformsbetterwithbracingswhichreducesdeflections andincreasesstabilityofthestructure.

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6. References:

[1] C. H. Lokesh Nishanth, Y. Sai Swaroop, D. C. K. Jagarapu,andP.K.Jogi,“Analysisanddesignofcommercial buildingwithdifferentslabarrangementsusingETABS,”in

[4] M.M.Baig,A.Rashid,Y.P.S.D.Reddy,andT.G.N.. V.Krishna,“AcomparativestudyonseismicanalysisofG+6 buildingwithribbedslab&conventionalslabusingSAP2000 software,” IOP Conf. Ser. Mater. Sci. Eng.,vol.1112,no.1,p. 012026, Apr. 2021, doi: 10.1088/1757899x/1112/1/012026.

[5] D.M.PatilandK.K.Sangle,“SeismicBehaviourof DifferentBracingSystemsinHighRise2-DSteelBuildings,” Structures, vol. 3, pp. 282–305, Aug. 2015, doi: 10.1016/j.istruc.2015.06.004.

[6] K.V.RathodandS.Gupta,“Anonlineartimehistory analysisoftenstoreyrccbuilding,” Int. Res. J. Eng. Technol., vol.7,no.June,pp.56–2395,2020.

[7] A.K.SawwalakheandP.D.Pachpor,“Comparative Study Of Conventional Slab, Flat Slab And Grid Slab Using ETABS,” IOP Conf. Ser. Mater. Sci. Eng., vol. 1197, no. 1, p. 012020, Nov. 2021, doi: 10.1088/1757899x/1197/1/012020.

[8] I.Standard,“lajpukvksaosQHkwdEijks/hfMtkbu osQ ekunaM Criteria for Earthquake Resistant Design of Structures,”vol.1893,no.December,2016.

[9] IS456,“PlainConcreteandReinforced,” Bur. Indian Stand. Dehli,pp.1–114,2000.

[10] Rathod,K.V.,&Gupta,S.(2020).Anonlineartime history analysis of ten storey RCC building. International Research Journal of Engineering and Technology, 8