Project 1

A residential society has 200 x 2BHK flats and 100 x 3BHK flats. A typical family in a 2BHK flat has 3 persons/flat and a 3BHK flat has 4 persons/flat. The gross water demand (per person per day in liters) can be calculated by taking the aggregate of the usage for all the below listed activities.

Activities	Consumption (per person/day in litres)
Drinking	5
Cooking	45
Bathing	30
Toilet Flushing	25
Cloth Washing	35
Miscellaneous use	10

As per given data total persons in the residential society is 1000.

Per day one person water usage is 150litres.

Total water consumbtion per day in residential society is 150000litres.

Constraints & Site Data:

• One of the dimensions of the underground water tank is limited by the width of the internal road in the residential society as this is the ideal location of an underground water tank in case of a fire emergency. The width of the road could be taken as 6 meters and thus the width dimension of the tank cannot exceed 6 meters.
• The bearing capacity of the soil at different founding depths is given in the table belo

Founding Depth (Below F.G.L)	S.B.C  (Tonnes/sqm)
-3.00 m LVL	7.5
-4.00 m LVL	8
-5.00 M LVL	8.5

Consider an allowable soil settlement of 25 mm under the base slab.

• The top cover slab thickness is 500mm for a maximum one-way direction span of 4 meters. Use a structural beam of dimensions 500 x 900 (min concrete grade M25) if the span of the top slab exceeds 4 meters in order to break the span. Note that the beam and the top slab doesn’t need to be designed under current problem statement.

Loadings:

• For the top cover slab, the maximum live load to be assumed is 15 kN/m2 and a maximum superimposed dead load is 3 kN/m2.
• Consider unit weight of soil 18 kN/m3 and unit weight of water 10 kNm3. The soil needs to be considered in a saturated state.

Create a full-scaled 3D STAAD pro model of the underground water tank complying with the calculated demand, site constraints and the best practice guidelines for FEA. The final model should consist of all the applicable loadings on the structure, support conditions, material specifications and an average mesh size of 500 mm. The modelling of the entire geometry shall be based on center line approach and the model should be devoid of any errors or warnings.

           Materials unit weight as per the code 

                               Safe Bearing Capacity = 18kN/m^3

                               Plain cement concrete = 24kN/m^3

                               Reinforced cement concrete = 25kN/m^3

                               Cement concrete screed = 20kN/m^3

                               Cement masonry = 22kN/m63

                               Structural steel = 78.5kN/m^3

               Loads of a building 

                               Slab weight = 3.75kN/m^2(0.15mx25kN/m^3)

                               Partitions = 1.5kN/m^2

                               Floor finish = 2.5kN/m^2

,                              Others = 1kN/m^2

                               Total floor load = 8.75kN/m^2

                Slab unit weights 

                              Slab weight = 3.75kN/m^2(0.15mx25kN/m^3)

                              Insulations and water proofing = 0.5kN/m^2

                              MEP services = 0.5kN/m^2

                              Others = 0.5kN/m^2

                              Total roof load = 5.25kN/m^2

              Common corridor = 3kN/m^2

              Total floor load =3kN/m^2

             Accessible roof = 1.5kN/m^2

              Total roof load = 1.5kN/m^2

    Design of slab(IS-456)

            Span shorter direction(clear) Ly = 3.125m

            Span longer direction(clear) Lx = 5.5m

            Live load on the slab(LL) = 3kN/m

            Compressive strength of concrete(Fck) = 25N/mm^2

            Yield strength of steel(Fy) = 415N/mm^2

            Unit weight of concrete(Yc) = 25kN/m^3

            Unit weight of floor finish 100mm(Y) = 22kN/m^3

            Clear concrete cover = 25mm

             Bearing slab(B) =250mm

Step - 1 

            Span to effective depth ratio L/d = 32

            Minimum effective depth(d) = 97.67mm

            Overall depth(D) = 127.66mm

            Dia of bars in shorter direction = 10mm

            Dia of bars in longer direction = 10mm

             Effective depth(d) = 120mm

   Loading on the slab

            Dead load of the slab(DL) = 3.75kN/m^2

            Super dead load = 5kN/m^2

            Live load on the slab = 3kN/m^2

            Total load on the slan = 11.75kN/m^2

            Design load = Total load x load factor

                              = 17.63kN/m^2

            Effective span Lx = 3.25m

                                  Ly = 5.62m

                                 Lx/Ly = 1.732 (two way)

         

	1.5	Alpha x	1.75	Alpha y
For negative moments (at top)	0.075	0.104683	0.107	0.084
For positive moments (at bottom)	0.056	0.103307	0.107	0.063

Step - 2

              BM per unit width of slab

	Mx=αxwLx^2	My=αywLy^2
For negative moments (at top)	19.43	15.59kN-m/m
For positive moments (at bottom)	19.17	11.69kN-m/m

 Shear force V = 0.5WLx =28.6 kN/m

Step - 3

               To check the effective depth of the slab 

                                     Mu,lim = 0.138Fckbd^2

                                            d = 74.55mm

Step - 4

              Depth of slab for shear force 

                                      Tc,max = 3.1N/mm^2

                                      Tc = 0.3

                                       K = 1.2

                                        D = 200mm

                                       Tc = 0.3N/mm^2

                                       Tv = Vu/bd

                                            = 0.24N/mm^2

                 Tv<tc<tc,nax< p=""></tc<tc,nax<>

                0.24<0.36<3.1

                  SAFE

Step - 5 

                 Determination of area of steel 

                                 Mu = 0.87FyAstd(1-AstFy/Fckbd)

                  For negative moment 

                                 Mutop = 19.43kN/m

                                  Ast = 561.65mm^2/m

                   For positive moment 

                                 Mubottom = 19.17kN/m

                                  Ast = 554.27mm^2/m

                 Determination of distribution steel 

                                  Astmin = 0.12bd

                                             = 114mm^2

                   Selection of steel reinforcing bars

                                  Area of bars(Top steel) = 78.5mm^2

                                                Spacing = 140mm

                                                            = 125mm

                               provide 16mm bqars at a spacing 125mm

                                    Area of bars(Bottom steel) = 78.5mm^2

                                                 Spacing = 142mm

                                                             =125mm

                                 Provide 16mm bars at a spacing 125mm

     Calculation of wind load (IS875-Part 3)

                          Design wind speed Vz = Vbk1k2k3k4 m/s

                           Basic wind speed(Bengalore) Vb = 33m/s

                           Probability factor k1 = 1

                           Terrain factor k2 = Category 4B

                           Topography factor k3 = 1

                           Design wind pressure Pz = 0.6Vz^2

 

Floor	Height	k2	Vz	Pz	Pz in kN
1	3.5	0.76	25	377.40	0.38
2	7	0.76	25	377.40	0.38
3	10.5	0.76	25	377.40	0.38
4	14	0.76	25	377.40	0.38
5	17.5	0.76	25	377.40	0.38
6	21	0.76	26	397.53	0.40
R	24.5	0.76	26	461.04	0.46

     Calculation of Seismic Load (IS1893-Part I)

 Design base shear VB = Ah x W 

        Where,

               Ah = horizontal seismic coefficient as calculated as per 6.4.2

                W = Total weight of the structure

     

        

    Zone factor Z = 0.1 (Bngalore)

   Soil condition factor Sa/g

                               

    Height of building h = 24.5m

    Base dimension of building 

                                             Along-X = 25m

                                             Along-Z = 16m

                                             T along-X = 0.5513sec

                                            T along-Z = 0.4410sec

                          

   Sa/g for hard soil = 1/T = 1.814 Along X

                                      = 2.268 Along Z

            Responce reduction factor R = 3

             Importance factor I = 1.2

     Horizontal accelaration co-efficient Ah = 0.0363

                                                            = 3.6812%

      Seismic weight

                  Area of each floor A = 400m2

                  Due to dead loads Typical floor DL = 12.5kN/m2

                                                             W DL = 5000kN

                  Due to dead loads, roof

                                                         DL roof = 9kN/m2

                                                      W DL roof = 3600kN

                   Due to live loads, Typical floor LL = 3kN/m2

                                                         W LL = 300kN/m2

                  Due to live loads, Roof LL = 1.5kN/m2

                                            W LL roof = 0

                 Total seismic weight W = 35400kN

                 Design base shear VB = AhxW

                                                 = 1605.44kN

,