alternative floor systems of a 20 storied concrete v3.0
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Alternative Floor Systems of a 20 Storied Concrete v3.0TRANSCRIPT
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 floor Two-way slab (With Edge Beam)
FLOOR SYSTEM 02
Flat Slab with Capital & Drop Two-way joist floors
FLOOR SYSTEM 03
RC JOIST
OPEN WEB JOIST-01
BENEFITS• Reduced construction time (save on rent and move in sooner).• Floor is easily accessible to accommodate wiring plumbing / AC Service. • All services such as plumbing and electrical are easily accessible after construction enabling alternations to be carried out.
OPEN WEB JOIST-02
BENEFITS• Efficient framing system • Economical and lightweight • Exceptionally high strength-to-weight ratio. • Minimize floor-to-floor heightsSince 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.
STEEL OPEN WEB JOIST - 01COMPONENTS
STEEL OPEN WEB JOIST - 02COMPONENTS
COMPOSITE STEEL JOIST - 01
DEFINITION
• 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 JOIST -02
BENEFITS
• 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 ANALYSIS
BEAM 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 PROPERTIES
Concrete : 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 SUPPORTED
Weight: 1138 kip / floor i.e 267 lb / sft
FLOOR PLAN – JOIST SUPPORTED
Weight: 878 kip / floor i.e 206 lb / sft
MEMBER DIMENSIONS
BEAM Supported slab (A) JOIST Supported slab (B)
Slab: 6inch Slab: 3.5inchBeam: 15x24inch Beam: 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 COMBINATION
RCC structure : BNBC 93 Joist (LRFD) : 1.4 DL (ASCE 2.3.2-1) 1.2 DL + 1.6 LL (ASCE 2.3.2-2)
CONCRETE & JOIST JOINT
OUTPUT 01BEAM Supported slab JOIST Supported slab
3.28 inch 3.14 inch
BEAM Supported slab JOIST Supported slab
28639 kip 23440 kip
TOP DEFLECTION
TOTAL BASE REACTION (Full Dead & Live Load)
BEAM Supported slab JOIST Supported slab
267lb/sft 206lb/sft
WEIGHT / sft (Dead Load Alone)
OUTPUT 02-A
Member Type
(A) RC Beam Supported Slab
(B) Joist Supported Slab % Saving
in BQuantity Unit Amount, TK
Quantity Unit Amount, TK
i) Concrete 483 cum 5859297 412 cum 5000564 14.66ii) Shutter 970 sqm 22219 867 sqm 19859 10.62iii) Rebar 116706 kg 11305321 106553 kg 10321758 8.70
SAVINGS IN COLUMN
OUTPUT 02-B
Member Type
(A) RC Beam Supported Slab
(B) Joist Supported Slab
% Saving in B
Quantity Unit Amount,
TKQuantity Unit Amount,
TK
i) Concrete 441 cum 5307032 403 cum 4846616 8.68ii) Shutter 484 sqm 12065 426 sqm 10618 12.00iii) Rebar 132194 kg 12805600 120693 kg 11691513 8.70
SAVINGS IN BEAM
OUTPUT 02-C
Member Type
(A) RC Beam Supported Slab
(B) Joist Supported Slab
% Saving in B
Quantity Unit Amount,
TKQuantity Unit Amount,
TK
i) Concrete 1370 cum 16850049 584 cum 7181791 57.38ii) Shutter 1266 sqm 30802 0 sqm 0 100.00iii) Rebar 161403 kg 15635061 64924 kg 6289182 59.78
SAVING IN SLAB
OUTPUT 02-D
Member Type
(A) RC Beam Supported Slab
(B) Joist Supported Slab
% Saving in BQuantity Unit Amount,
TKQuantity Unit Amount,
TK
i) Concrete 1613.39 cum 18679772 1473.02 cum 17054631 8.70ii) Boring 5700.00 rm 6891300 5278.20 rm 6381344 7.40iii) Rebar 145181 kg 14063693 130662.98 kg 12657323 10.00
SAVING IN FOUNDATION
OUTPUT 02-E
Member Type
(A) RC Beam Supported Slab
(B) Joist Supported Slab
% Saving in BQuantity Unit Amount,
TKQuantity Unit Amount,
TK
i) Joist 0.00 Ton 0 77.00 Ton 6970000 (100)ii) Metal Deck 0.00 Ton 0 45.00 Ton 5400000 (100)
ADDITIONAL COST IN RC JOIST
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-AJOIST CALCULATION - 01
DESIGN DATA:JOIST ID : 14K6 (7.7lb/ft)Design Code : SJI 2010Design Type : LRFDMaterial criteria : 50ksi
OUTPUT 03-BJOIST CALCULATION - 02
LoadDL-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 04JOIST ALLOWABLE LOAD TABLE
ESTIMATE 01SOURCE: PWD 2014
ABSTRACT OF COST (CONSIDERING RC BEAM SUPPORTED SLAB)
A. CIVIL WORKS: Tk. 118972404
Tk. 118972404
Add @ 5% contingency Tk. 5948620
Total Tk. 124921024
Say Tk. 124,921,100
Rate / sft 1,470
Floor area: 4250 sft (20 Storied Bldg)
ESTIMATE 02SOURCE: PWD 2014
ABSTRACT OF COST (CONSIDERING OPEN WEB JOIST SUPPORTED SLAB)
A. CIVIL WORKS: Tk. 10520996Tk. 105209960
Add @ 5% contingency Tk. 5260498Total Tk. 110470458
Say Tk. 110,470,500.00
Rate / sft 1,300
Floor area: 4250 sft (20 Storied Bldg)
ESTIMATE 03SOURCE: PWD 2014
SLAB TYPE Cost /sft
RC BEAM SUPPORTED SLAB Tk1470
STEEL JOIST SUPPORTED SLAB Tk1300
SLAB TYPE Weight / floor
RC BEAM SUPPORTED SLAB 1138 kip (267lb/sft)
STEEL JOIST SUPPORTED SLAB 878 kip (206lb/sft)
CONCLUSION1. 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.
2. 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 .