DESIGN OF FLAT SLAB USING IS 456 & ACI 318 AND COMPARISION

PRESENTATION ON DESIGN AND COMPARISON OF FLAT SLAB USING IS 456 2000 AND ACI 318 08

PRESENTED BYTUSHAR MANOJ MADAMWAR(11001063)GUIDED BYDR. K. N. KADAMCONTENTSINTRODUCTIONADVANTAGES OF FLAT SLABLITERATURE REVIEWDESIGNOF FLAT SLAB USING IS 456-2000DESIGN OF FLAT SLAB USING ACI 318-08RESULT AND COMPARISIONREFERENCES

INTRODUCTIONDEFINATION-Slab and column without beamsCOMPONENTS - Drops-increase shear strength against punching. - Column Head-resists negative moment

Advantages of Flat SlabFlexibility in room layoutSaving in building heightShorter construction timeEase of installationPre-fabricated welded meshBuildable scorePROBLEM STATEMENTDESIGN OF FLAT SLAB USING IS 456-2000Column Strip A design strip having a width of 0.25l2 not greater than 0.25l1 on each side of column center-line.For longer span=1.4m (not greater than 1.65)For shorter span=1.65m(not greater than 1.4)

Middle strip A design strip bounded on each of its opposite sides by the column strip.For longer span=2.8mFor shorter span=3.8m

Panel The part of a slab bounded on-each of its four sides by the center-line of a Column or center-lines of adjacent-spans.

Total design moment on slabTotal Design LoadFor longer span(l n=5.448 m , l2 =5.6 m)= W = w l 2 l n =471.36kNFor shorter span(l n=4.44 m , l2 =6.6 m)=W = w l2 ln= 452.74k N

Absolute Sum of Negative and Positive MomentsStiffness CalculationsDistribution of Bending Moment Across The Panel WidthEffective Depth of The SlabShear In Flat SlabReinforcementDESIGN OF FLAT SLAB USING ACI 318-08Designed Load on SlabTotal factored static moment for a spanBending moment for column stripNegative moment for column strip = 75 % of total negative moment in the pannel= 0.75 x 154.00 = 115.50 ft -kips = 157.66 KNmPositive moment for column strip = 60 % of total positive moment in the panel.= 0.60 x 83.00 = 49.8 ft -kips = 67.977 KNmMax moment (+ve or ve ) along shorter span = 72.18 ft -kipsMax moment (+ve or ve) along longer span = 115.50 ft kipsShear ProvisionReinforcementResults and ComparisonsCODEIS 456 -2000ACI 318-08Shape of test specimen for concrete strength (mm)Cube150x150x150Cylinder152.4x304.8Grade of concrete(N/mm)2020Grade of steel (N/mm)415413.7Negative moment(KN-m)188.5208.89Positive moments(KN-m)90113.22Area of reinforcement(mm)42902829Thickness of slab forServiceability criteria(mm)170150Punching shearSafeSafeConclusions By comparing with different codes we concluded that ACI 318 code is more effective in designing of flat slabs. As per Indian code we are using cube strength but in international standards cylinder strength is used which gives higher strength than cube. Drops are important in increasing the shear strength of the slab.Flat slabs enhance resistance to punching failure at the junction of concrete slab & column. By incorporating heads in slab, we are increasing rigidity of slab.In the interior span, the total design moments (Mo) are same for IS, ACI.

ConclusionsThe negative moments section shall be designed to resist the larger of the two interior negative design moments for the span framing into common supports.According to Indian standard (IS 456) for RCC code has recommended characteristic strength of concrete as 20, 25, and 30 and above 30 for high strength concrete. For design purpose strength of concrete is taken as 2/3 of actual strength this is to compensate the difference between cube strength and actual strength of concrete in structure. After that we apply factor of safety of 1.5. So in practice Indian standard actually uses 46% of total concrete characteristic strength. While in International practice is to take 85% of total strength achieved by test and then apply factor of safety which is same as Indian standard so in actual they use 57% of total strength. Pre fabricated sections to be integrated into the design for ease of construction.

ReferencesBureau of Indian Standards, New Delhi, IS 456:2000, Plain and Reinforced Concrete - Code of Practice, Fourth Revision, July (2000).American Concrete Institute, ACI 318-08, Building Code Requirements for Structural Concrete and Commentary, January (2008). Dr. V. L. Shaha & Dr. S. R. Karve Limit State Theory and Design of Reinforced Concrete Sixth editionAmit A. Sathwane , R. S. Deoalate (IJERA)Analysis and Design of Flat Slab and Grid Slab and Their cost omparision