Sheet1ReferenceCalculationOutputDesign of FoundationsA mat foundation was designed as the foundation for this structure.First of all general arrangement drawings for all floors were prepared forarchitectural drawings. Then column positions were determined andservice loads for columns were calculated.Finding geometric center:After preparing the outline drawings of the foundation, geometric centrefor the foundation was found. Geometric center for foundation ismarked in figure 5-1.Geometric centerx = 15.570y = 12.336Finding load center:To find the load center of the building, service loads for each column wascalculated. Transfering moments to the foundations was eleminatedby having a pin joint for frames at foundation level. Hence for designof foundations, only the axial loads of columns were used.Specimen claculation for calculating axial force of columnColumn K6:Effective area=5.3x2=10.6m2Self weight of slab=0.15*24=3.6kN/m2Finishes=1.0kN/m24.6kN/m2Total slab load per floor=4.6*10.6=49kNSelf weight of beams=(0.3*0.4*24*7.3)=21kNSelf weight of walls=5.2*2.95*5.3=81.3kNSelf weight of column=0.5*0.5*24*2.95=17.7kNTotal column dead load per floor=49+21+81.3+17.7=169kNTotal dead load for nine floors=169*9gk=1521kN=1521kNProject- DahampayaFeatureDesign of FoundationDECDESIGN UNITDesignedDateEPC DIVISIONCheckedDateCENTRAL ENGINEERING CONSULTANCY BUREAU (CECB)Job CodeD-676Page01 of 10Imposed load per floor=3.5kN/m2Total column imposed load per floor=3.5*10.6=37.1 kN/m2Total imposed load for nine floors=37.1*9qk=334kN=334kNSimillary axial forces for other columns were also calculated.To get the wind effect to the building, wind forces for each frame werealso calculated. Two static wind cases, called wind1 and wind 2 wereconsidered for wind from front and rear direction of the building.( Specimen calculations for wind analysis are shown under the Chapter 4of frame analysis section.)Building was modeled in "Etab" software to get the service axial forcesand column reactions. Following load cases were considered.Load 1).Dead+ LiveLoad 2).Dead+ Wind1Load 3).Dead+ Wind2Load 4).Dead+Live+ Wind1Load 5).Dead+ Live+Wind2For find the load center of the building, column reactions from serviceloads were considered.By considering above load cases, it could be clearly stated that,cases 2 and 3 would not be critical compare with cases.Hence loadcenter was found for the load case 1, 4 and 5.Calculations for finding load center are tabulated in Table 5-1x= F.xy= F.y x yLoad center for Dead+ Livex = 13.7613.77y = 13.4113.5Load center for Dead+ Live+Wind1x = 13.72y = 13.35Load center for Dead+ Live+Wind2x = 13.79y = 13.65Load centers and geometric center are located in figure 5-1It was observed that, geometric center and load center were not coincide.As the load center of the building cannot be changed, geometric centerwas tried to change by extending the raft foundation area.Project- DahampayaFeatureDesign of FoundationDECDESIGN UNITDesignedDateEPC DIVISIONCheckedDateCENTRAL ENGINEERING CONSULTANCY BUREAU (CECB)Job CodeD-676Page02 of 10Extending the foundation was not possile in some areas as the limitedspace of the site.Location of new geometric center after introducing cantilever parts to thefoundation is shown in the figure 5-2. Difference between thegeo-metric center and load center was still observed.Calculation of stress variation below raft foundation:For "Dead+ Live" condition:Geometric center=( 15.421 , 12.696 )Load center for "Dead+Live"=( 13.770 , 13.500)Ecentricity in "X" direction=15.421 - 13.770=1.651Ecentricity in "Y" direction=12.696-13.50=(-0.804)Pressure under foundation=F+MAZMxx=F . exMyy=F . ey=68168*1.651=68168*0.804=1.12x105kNm=0.55x105 kNmZ=I/YIxx=4x1016Iyy=6x1016Neutral axis lies through the centroid of the building.x=31.350-15.421y=25.250-12.696=15.929=12.554Zxx=Ixx/xZyy=Iyy/y=4x1016=6x10161592912554=2.51x1012 mm3=4.78x1012 mm3Project- DahampayaFeatureDesign of FoundationDECDESIGN UNITDesignedDateEPC DIVISIONCheckedDateCENTRAL ENGINEERING CONSULTANCY BUREAU (CECB)Job CodeD-676Page03 of 10Bending about X axis=F+MAZ=68168+1.12x1057.5 x1022.51x103=90.9+44.6=135.5< 150 kN/m2( Allowable bearingBending aboutYaxiscapacity of soil)=F+MAZ=68168+0.55x1057.5 x1024.78x103=90.9+11.5=102.5< 150 kN/m2( Allowable bearingcapacity of soil)For "Dead+Live+Wind1" condition:Geometric center=( 15.421 , 12.696 )Load center for "W1"=( 13.720 , 13.350 )Ecentricity in "X" direction=15.421 - 13.720=1.701Ecentricity in "Y" direction=12.696-13.350=(-0.654)Pressure under foundation=F+MAZMxx=F . exMyy=F . ey=67894*1.701=67894*0.654=1.15x105kNm=0.44x105 kNmZxx=2.51x1012 mm3Zyy=4.78x1012 mm3Project- DahampayaFeatureDesign of FoundationDECDESIGN UNITDesignedDateEPC DIVISIONCheckedDateCENTRAL ENGINEERING CONSULTANCY BUREAU (CECB)Job CodeD-676Page04 of 10Bending about X axis=F+MAZ=67894+1.15x1057.5 x1022.51x103=90.5+45.8=137< 150 kN/m2( Allowable bearingBending aboutYaxiscapacity of soil)=F+MAZ=67894+0.44x1057.5 x1024.78x103=90.5+9.2=99.7< 150 kN/m2( Allowable bearingcapacity of soil)For "Dead+Live+Wind2" condition:Geometric center=( 15.421 , 12.696 )Load center for "W2"=( 13.790 , 13.650 )Ecentricity in "X" direction=15.421 - 13.790=1.631Ecentricity in "Y" direction=12.696-13.650=(-0.954)Pressure under foundation=F+MAZMxx=F . exMyy=F . ey=68675*1.631=68675*0.954=1.12x105kNm=0.66x105 kNmZxx=2.51x1012 mm3Zyy=4.78x1012 mm3Project- DahampayaFeatureDesign of FoundationDECDESIGN UNITDesignedDateEPC DIVISIONCheckedDateCENTRAL ENGINEERING CONSULTANCY BUREAU (CECB)Job CodeD-676Page05 of 10Bending about X axis=F+MAZ=68675+1.12x1057.5 x1022.51x103=91.6+44.6=136.2< 150 kN/m2( Allowable bearingBending aboutYaxiscapacity of soil)=F+MAZ=68675+0.66x1057.5 x1024.78x103=91.6+13.8=105.4< 150 kN/m2( Allowable bearingcapacity of soil)It could be observed that, the total stress under the foundation due to axialand moment loading effect is always less than bearing capacity of soil.Further calculations show that no negative pressure will develop underthe loading conditions.Hence raft foundation could be designed for allowable bearing capacityof soil.Design of Foundations:Analysis of raft foundation was done by using "Etab" software.Finite element method was used to determine the bending momentsand shear forces of raft slab.Raft slab was designed as slabs with shell elements. Axial loads ofcolumns were given as point loads to the foundation. Perimeter basementwalls were also modeled as structural wall element around the foundation.Cantilever parts of the foundation were also modeled as shell elements asit reduces the bending moments of the foundation. Subgrade coefficientof soil was calculated and reprenseted soil stiffiness by area springs.Sub grade reaction of soil (ks):Allowable bearing capacity of soil is 150kN/m2 and allowable deflectionis 75mm according to the soil investigations.ks=qult=qa x S.F.=150x30.075=6000kN/m3Project- DahampayaFeatureDesign of FoundationDECDESIGN UNITDesignedDateEPC DIVISIONCheckedDateCENTRAL ENGINEERING CONSULTANCY BUREAU (CECB)Job CodeD-676Page06 of 10The analysis input data and out put data are attached here with.Design of foundation:Design for moments:Specimen calculation for sagging moments:Consider column strip "4":Maximum moment at column strip "4" at grid "H":=900kNmBS 8110k=M=900x106Cl. 3.4.4.4bd2.fcubd2.fcub=1000 mmd=800-45-25-25/2=717mmfcu=30 N/mm2k=900x106=0.058vc +0.4Hence shear r/f is required.Cl. 3.7.7.5Asv sin>(v-vc)ud0.87.fyv=90Asv>0.43x2000x7420.87x460Provide shear>1595mm2linksT12 @150mm(Provide T12 @ 150mm spacing evenly around the column perimeter)Shear force around 1.5d perimeter:U0=4*1.5*742mm=4450mmProject- DahampayaFeatureDesign of FoundationDECDESIGN UNITDesignedDateEPC DIVISIONCheckedDateCENTRAL ENGINEERING CONSULTANCY BUREAU (CECB)Job CodeD-676Page09 of 10(vmax) 1.5m=1375 x1034450x742=0.416 kN/m2