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 has 4 persons/flat. The gross water demand (per person per day in liters) can be calculated by taking the aggregate if the usage for all the below listed activities.

Activities Consumption (per person/day in liters)

Drinking 5

Cooking 45

Bathing 30

Toilet Flushing 25

Cloth Washing 35

Miscellaneous 10

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

Per day one person water usage is 150 liters.

Total water consumption per day in residential society is 150000 liters.

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 below.

Founding Depth (below F.G.L) S.B.C (tones/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 has a maximum one-way direction span of four meters and a thickness of 500mm. If the top slab span is greater than 4 meters, use a structural beam with dimensions of 500 by 900 (minimum concrete grade M25) to break the span. It should be noted that the current problem statement does not require the design of the beam or the top slab.
  

Loadings:

• The maximum superimposed dead load for the top cover slab is 3 KN/m2, and the maximum live load that should be considered is 15 KN/m2.
  
• Think about the weight of water in units of 10 kNm3 and soil in units of 18 KN/m3. It is necessary to take into account the soil's saturation level.
  

Make a full-scaled 3D STAAD pro model of the subterranean water tank that complies with the site's limitations, the estimated demand, and the FEA best practice recommendations. All relevant loadings on the structure, support conditions, material specifications, and an average mesh size of 500 mm should be included in the final model. The center line technique will be used to model all of the geometry, and the model must be error- and warning-free.

Materials unit weight as per the code

Safe Bearing Capacity = 18 KN/m^3

Plain cement concrete = 24 KN/m^3

Reinforcement concrete = 25 KN/m^3

Cement concrete screed = 20 KN/m^3

Cement masonry = 22 KN/m^3

Structural steel = 78.5 KN/ m^3

Loads of a building

Slab weight = 3.75KN/m^2(0.15mx25KN/m^3)

Partitions = 1.5 KN/m^2

Floor finish = 2.5 KN/m^2

Others = 1 KN/M^2

Total floor load = 8.75KN/m^2

Weights of slab units

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

Waterproofing and insulations = 0.5 KN/m^2.

Services for MEP = 0.5kN/m^2.

Others = 0.5kN/m^2.

Roof load total = 5.25 KN/m^2

Shared corridor: 3 KN/m^2.

Floor load total = 3kN/m^2.

Roof accessibility = 1.5 KN/m^2.

Roof load total = 1.5 KN/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

L/d = 32 is the span to effective depth ratio.

Effective depth minimum (d) = 97.67 mm.

Depth total (D) = 127.66 mm.

Bars' diameter in the shorter direction = 10 mm.

Bar diameter in the extended direction = 10 mm.

120mm is the effective depth(d).

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 slab

Mu,lim = 0.138Fck bd^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 = 200 mm

Tc = 0.3N/mm^2

Tv = Vu/bd

= 0.24/mm^2

Tv

0.24<0.36<3.1

SAFE

Step - 5

Estimating the steel's area
Mu = 0.87FyAstd(Fck bd - 1-AstFy)

For negative moment

Mu(top) = 19.43 KN/m

Ast = 561.65mm^2/m

For positive moment

Mu(bottom) = 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 bars 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(Bangalore) 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 1)

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 (Bangalore)

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

Response reduction factor R = 3

Importance factor I = 1.2

Horizontal acceleration 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 = Ah x W

= 1605.44kN