Alternative Floor Systems of a 20 Storied Concrete v2.0

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Alternative Floor Systems of a 20 Storied Concrete v2.0

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  • ALTERNATIVE FLOOR SYSTEMS OF A 20 STORIED CONCRETE BUILDING

  • FLOOR SYSTEM 01 One-way slab, supported by (i) Monolithic concrete beams(ii) Steel beams One-way slab with cold-formed steel decking and reinforcement One-way joist floor (also known as ribbed slab) Two-way slab supported by edge beams Flat slabs /plate(i) With column capitals or drop panels or both, but without beams(ii)without beams and with no drop panels or column capitals Two-way joist floors, with or without beams on the column lines

  • One-way slab (Steel or RC Beams)One-way slab with cold-formed steel decking One-way Joist floorTwo-way slab (With Edge Beam)FLOOR SYSTEM 02

  • Flat Slab with Capital & DropTwo-way joist floorsFLOOR SYSTEM 03

  • RC JOIST

  • STEEL OPEN WEB JOISTBENEFITS

    Efficient framing system Economical and lightweight Exceptionally high strength-to-weight ratio. Minimize floor-to-floor heights

    Since steel joists are lighter than wooden / RC materials, the size of the supporting structural elements as well as the size of the building's foundation can be reduced for cost efficiency.

  • COMPOSITE STEEL JOISTDEFINITION

    Joist top chord and overlying concrete slab will actas an integral unit once the concrete has cured.

    Welded shear studs to ensure adequate transfer of shear

    Simplified erection, faster connections, and minimal crane lifts occur.

  • COMPOSITE STEEL JOISTBENEFITS

    A more efficient and stiffer composite design makes it possible to support a given load with a shallower joist

    Weight savings from the joist design reduces building costs

    Simplified erection, faster connections, and minimal crane lifts occur.

  • COMPARATIVE ANALYSISBEAM SUPPORTED AND JOIST SUPPORTED SLAB.

  • CODE & MATERIALCODE AND STANDARD

    Steel Joist Institute (SJI) 2010 Bangladesh National Building Code - 1993 (BNBC) American Institute of Steel Construction

    MATERIAL PROPERTIESConcrete: fc = 4,000 psi.Reinforcement: fy =72,500 psi.Steel Joist : fy = 50,000psi.

    Fire Safety & Floor Vibration have not been considered in Joist supported slab.

  • FLOOR PLAN BEAM SUPPORTEDWeight: 1138 kip / floor i.e 267 lb / sft

  • FLOOR PLAN JOIST SUPPORTEDWeight: 878 kip / floor i.e 206 lb / sft

  • MEMBER DIMENSIONS

    BEAM Supported slab (A)JOIST Supported slab (B)Slab: 6inchSlab: 3.5inchBeam: 15x24inchBeam: 12X21 inch & 15x24inchColumn:36x36inch (GF-6th) 30x30inch (7th-12th) 24x24inch (13th-Roof)Column:33x33inch (GF-6th) 27x27inch (7th-12th) 20x20inch (13th-Roof)Pile Length: 120ft (Cap: 100T)Pile Length: 105ft (Cap: 90T)-Joist : 14K6 (7.7lb/ft)

  • LOADSDEAD

    Self weight & SDEAD load of 60psf. Live Load: 60psf Wind Load: BNBC 93, (210kph, Exposure A) Seismic: BNBC 93 (Zone: 2, I : 1, R:8)

    LOAD COMBINATIONRCC structure: BNBC 93 Joist (LRFD): 1.4 DL (ASCE 2.3.2-1) 1.2 DL + 1.6 LL (ASCE 2.3.2-2)

  • OUTPUT 01

    TOP DEFLECTIONTOTAL BASE REACTION (Full Dead & Live Load)WEIGHT / sft (Dead Load Alone)

    BEAM Supported slabJOIST Supported slab3.28 inch3.14 inch

    BEAM Supported slabJOIST Supported slab28639 kip23440 kip

    BEAM Supported slabJOIST Supported slab267lb/sft206lb/sft

  • OUTPUT 02-ASAVINGS IN COLUMN

    Member Type(A) RC Beam Supported Slab(B) Joist Supported Slab% Saving in BQuantity UnitAmount, TKQuantity UnitAmount, TKi) Concrete483cum5859297412cum500056414.66ii) Shutter970sqm22219867sqm1985910.62iii) Rebar116706kg11305321106553kg103217588.70

  • OUTPUT 02-BSAVINGS IN BEAM

    Member Type(A) RC Beam Supported Slab(B) Joist Supported Slab% Saving in B

    Quantity UnitAmount, TKQuantity UnitAmount, TKi) Concrete441cum5307032403cum48466168.68ii) Shutter484sqm12065426sqm1061812.00iii) Rebar132194kg12805600120693kg116915138.70

  • OUTPUT 02-CSAVING IN SLAB

    Member Type(A) RC Beam Supported Slab(B) Joist Supported Slab% Saving in B

    Quantity UnitAmount, TKQuantity UnitAmount, TKi) Concrete1370cum16850049584cum718179157.38ii) Shutter1266sqm308020sqm0100.00iii) Rebar161403kg1563506164924kg628918259.78

  • OUTPUT 02-DSAVING IN FOUNDATION

    Member Type(A) RC Beam Supported Slab(B) Joist Supported Slab% Saving in B

    Quantity UnitAmount, TKQuantity UnitAmount, TKi) Concrete1613.39cum186797721473.02cum170546318.70ii) Boring5700.00rm68913005278.20rm63813447.40iii) Rebar145181kg14063693130662.98kg1265732310.00

  • OUTPUT 02-EADDITIONAL COST IN RC JOIST

    Member Type(A) RC Beam Supported Slab(B) Joist Supported Slab% Saving in B

    Quantity UnitAmount, TKQuantity UnitAmount, TKi) Joist0.00Ton077.00Ton6970000(100)ii) Metal Deck0.00Ton045.00Ton5400000(100)

  • OUTPUT 02 SUMMARY (A-E)

    COST SAVING IN CONCRET & REINFORCEMENT

    9% saving in Joist slab for column / wall. 9% saving in Joist slab for beam & foundation. 55-60% saving in Joist supported slab. (Without considering joist cost) 25% saving in Joist supported slab (Considering joist cost)

    Overall 12~13% cost saving in Joist Supported Slab

  • OUTPUT 03-A

    JOIST CALCULATION - 01DESIGN DATA:JOIST ID:14K6 (7.7lb/ft)Design Code:SJI 2010Design Type:LRFDMaterial criteria:50ksi

  • OUTPUT 03-B

    JOIST CALCULATION - 02LoadDL-Dead Load : 3.5 slab = 44psf SDEAD = 60psfLL-Live load : 60 psfFactored Load : 1.2DL+1.6LL = 124.8 + 96 ~ 220.8psfFactored Load / ft of Joist : 220.8*3.62 lb/ft = 800lb/ft + 7.7lb/ft = 807.7lb/ft. Allowable Load:825 lb/ft >807.7lb/ft SAFE

  • OUTPUT 04

    JOIST ALLOWABLE LOAD TABLE

  • ESTIMATE 01

    SOURCE: PWD 2014Floor area: 4250 sft (20 Storied Bldg)

    ABSTRACT OF COST (CONSIDERING RC BEAM SUPPORTED SLAB)A. CIVIL WORKS:Tk.118972404Tk.118972404Add @ 5% contingency Tk.5948620Total Tk.124921024Say Tk. 124,921,100Rate / sft 1,470

  • ESTIMATE 02

    SOURCE: PWD 2014Floor area: 4250 sft (20 Storied Bldg)

    ABSTRACT OF COST (CONSIDERING OPEN WEB JOIST SUPPORTED SLAB)A. CIVIL WORKS:Tk.10520996Tk.105209960Add @ 5% contingency Tk.5260498Total Tk.110470458Say Tk. 110,470,500.00 Rate / sft 1,300

  • ESTIMATE 03

    SOURCE: PWD 2014

    SLAB TYPECost /sftRC BEAM SUPPORTED SLABTk1470STEEL JOIST SUPPORTED SLABTk1300

    SLAB TYPEWeight / floor RC BEAM SUPPORTED SLAB1138 kip (267lb/sft)STEEL JOIST SUPPORTED SLAB878 kip (206lb/sft)

  • CONCLUSION

    Saving in cost has observed in steel joist supported slab for about 15% in column / wall, 8% in beam & foundation, near about 55-60% in slab.

    Additional cost shall imply for steel joist, decking sheet etc for Joist supported slab. It is worth to note that Fire issue and Vibration analysis has not been considered in Joist supported slab. This consideration might lead to additional cost .

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