stair case
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Stair case
DATA sheetBase on B.C.Punmia book RCCdesign exmpale 8.2DESIGN OF DOG-LEGGED STAIRName of work :-pkn1Stair hall measure3.00x1.20m2Available verical space between floor2.50m2500mm3Horizontal Span of stair case1.20mtr1200mm4Risers0.15mtr150mm5Treads0.25mtr250mm6ConreteM -20wt. of concrete25000N/m3scbc7N/mm2m13.337Steelfy415sst230N/mm28Nominal cover25Effective cover30mmReinforcementMain Bottom slab10mm F bars150mm c/cAnchor bars (Bottom )8mm F bars2Nos.Strirrups8mm F bars370mm c/c10mm f300mm c/c-917916.666666666712001500.70250120010mm f150mm c/c2.501508mm f370mm c/c2501.8010mm f300mm c/[email protected]
Design151152045334418402041204018401634163426DESIGN OF DOG-LEGGED STAIRName of work :-pknStair hall measure3.00x1.20Available verical space between floor2.50mHorizontal Span of stair case1.20m1200mmRisers0.15m150mmTreads0.25m250mmConcreteM-20wt. of concrete25000N/mm2scbc7m13.33Steelfy-415N/mm2sst230N/mm2Nominal cover25mmEffective cover30mm3.001Genral arrngment:-1.20Fig. shows plan of stair hall.Height of 1st flight.=2.50/2=1.25mminimum1.8mwhich is heigherNo. of risers required=1.80/0.15=12No. in 1st flight.2.75No. of treads required=12-1=11No. in 1st flight.UPSpce occupied by treads=11x0.25=2.75m1.20Keep width of landing equal to=1.20m\ Space left for passage=-2.75mHeight of 1st flight.=0.70mNo. of risers required=0.70/0.15=4.6666666667No. in 2nd flight.No. of treads required=4.6666666667-1=3.6666666667No. in 2nd flight.Spce occupied by treads=3.6666666667x0.25=0.9166666667mKeep width of top landing=m2Design Constants:-For HYSD BarsCocrete M=20-2.75sst=230N/mm2wt. of concrete=25000N/mm2scbc=7N/mm3m=13.33k =m*c=13.33x7=0.289m*c+sst13.33x7+230j =1-k/3=1-0.289/3=0.904R =1/2xc x j x k=0.5x7x0.904x0.289=0.9133Loading Each Flight :-The landing slab is assume to span in the same direction as stair, and is consideredas acting together to form a single slab. Let the bearing of landing slab in wall be=160mmThe effective span=2.75+1.20+(0.16/2)'=4.03msay=4.00mLet the thickness of waist slab '=1.20x40=48mm\Weight of slab w' on slope=0.048x1x1x25000=1200N/m2Dead weight of horizontal area w1= w'xR2+T2=1200x1502+2502=1399N/m2T250Dead weight of step is w2=1x150x25000=1875N/m21000\ Total Dead weight per meter run=3274NWeight of fiishing etc.=100NLive load=2500NTotal weight=5874NNote. The load w on the landing portion will be5874-1875=3999N, since weight of step will not come on it. However,a uniform value of w has been adopted [email protected] of waist slab :-wl2=5874x4.002=11748N-mB.M.=88Effective depth required=BM=11748000=113mmRxb0.913x1000But available=113+2x cover =25=138mmsay=140mm5Reinforcement:-Ast =BM x 100=11748000=498.20mm2sst x j x D230x0.904x11311using10mm F barsA=3.14xdia2=3.14x10x10=79mm24 x1004x10010Nomber of Bars=498x1.20=8No78.5098mm F c/c370Spacing=1200/8=150mm c/cHence used10mm F bars=150mm c/c8Distribution steel=0.12x113x1000=136mm271000mm F c/c0using8mm F barsA=3.14xdia2=3.14x8x8=50mm264 x1004x100250Spacing=50x1000=370mm c/c1.255136.13150Hence used8mm F bars=370mm c/c4321Foor [email protected]
Assume @ 40 to 50 mm per meter [email protected][email protected]
DrawingDESIGN OF DOG-LEGGED STAIR3.001.202.75UP1.20-2.751.20111098mm F c/c370870mm F c/c0625051504321Foor level1.202.75-2.75-917916.666666666712001500.70250120010mm f150mm c/c2.5008mm f370mm c/[email protected]
IS-TableVALUES OF DESIGN CONSTANTSPermissible Bond stress Table tbd in concrete (IS : 456-2000)Grade of concreteM-15M-20M-25M-30M-35M-40Grade of concreteM-10M-15M-20M-25M-30M-35M-40M-45M-50Modular Ratio18.6713.3310.989.338.117.18tbd (N / mm2)--0.60.80.911.11.21.31.4scbc N/mm2578.51011.513m scbc93.3393.3393.3393.3393.3393.33(a) sst = 140 N/mm2 (Fe 250)kc0.40.40.40.40.40.4Development Length in tensionjc0.8670.8670.8670.8670.8670.867Rc0.8671.2141.4741.7341.9942.254Grade of concretePlain M.S. BarsH.Y.S.D. BarsPc (%)0.71411.2141.4291.6431.857tbd (N / mm2)kd = Ld Ftbd (N / mm2)kd = Ld F(b) sst = 190 N/mm2kc0.3290.3290.3290.3290.3290.329M 150.6580.9660jc0.890.890.890.890.890.89M 200.8441.2845Rc0.7321.0251.2441.4641.6841.903M 250.9391.4440Pc (%)0.4330.6060.7360.8660.9971.127M 301351.636(c ) sst = 230 N/mm2 (Fe 415)kc0.2890.2890.2890.2890.2890.289M 351.1321.7633jc0.9040.9040.9040.9040.9040.904M 401.2291.9230Rc0.6530.9141.111.3061.5021.698M 451.3272.0828Pc (%)0.3140.440.5340.6280.7220.816M 501.4252.2426(d) sst = 275 N/mm2 (Fe 500)kc0.2530.2530.2530.2530.2530.253jc0.9160.9160.9160.9140.9160.916Rc0.5790.8110.9851.1591.3321.506Pc (%)0.230.3220.3910.460.530.599Permissible shear stress Table tv in concrete (IS : 456-2000)100AsPermissible shear stress in concrete tv N/mm2Permissible stress in concrete (IS : 456-2000)bdM-15M-20M-25M-30M-35M-40Grade of concretePermission stress in compression (N/mm2)Permissible stress in bond (Average) for plain bars in tention (N/mm2)< 0.150.180.180.190.20.20.2Bending acbcDirect (acc)0.250.220.220.230.230.230.23(N/mm2)Kg/m2(N/mm2)Kg/m2(N/mm2)in kg/m20.500.290.300.310.310.310.32M 103.03002.5250----0.750.340.350.360.370.370.38M 155.05004.04000.6601.000.370.390.400.410.420.42M 207.07005.05000.8801.250.400.420.440.450.450.46M 258.58506.06000.9901.500.420.450.460.480.490.49M 3010.010008.08001.01001.750.440.470.490.500.520.52M 3511.511509.09001.11102.000.440.490.510.530.540.55M 4013.0130010.010001.21202.250.440.510.530.550.560.57M 4514.5145011.011001.31302.500.440.510.550.570.580.60M 5016.0160012.012001.41402.750.440.510.560.580.600.623.00 and above0.440.510.570.60.620.63Maximum shear stress tc.max in concrete (IS : 456-2000)Grade of concreteM-15M-20M-25M-30M-35M-40tc.max1.61.81.92.22.32.5