3.2.6 Combined Footing

Combined Footing Analysis and Design P1 Dimensions:

P2

M1 Col 1

Col 2

Length, x (m)

0.40

0.45

Width, y (m)

0.40

0.45

Distance, xp (m)

5.5

Distance, xb (m)

0.4

Distance, xa (m)

0.8

M2 fy d

Col. 1

Col. 2

b

a

Material Properties: Concrete strength, f'c (Mpa)

20.0

Tensile strength, fy (Mpa)

276

Allow soil pressure, qa (kPa)

Xb

Xp

240.0

Xa

L

Loads Service Loads Col Loads

DL

LL

Wind

Eq

Assume weight of footing as 10% of column loads

P1(kN)

935.0

625.0

0.0

0.0

P2(kN)

1070.0

715.0

0.0

0.0

M1(kN-m)

0.0

0.0

0.0

0.0

M2(kN-m)

0.0

0.0

0.0

0.0

Load Case

1

2

3

4

P1(kN)

2371.50

841.50

1778.63

1778.63

Case 1: 1.4DL + !.7LL

P2(kN)

Case 2: 0.9DL + 1.3WL

Factored Loads

2713.50

963.00

2035.13

2035.13

M1(kN-m)

0.00

0.00

0.00

0.00

Case 3: 0.75(1.4DL + 1.7LL + 1.7WL)

M2(kN-m)

0.00

0.00

0.00

0.00

Case 4: 0.75(1.4DL + 1.7LL + 1.87EQ)

Suggested Footing Dimensions Width Left,b (m) Width Right,a (m) Area (m2)

2.30

Distance, Xb (m)

0.4

2.30

Distance, Xa (m)

0.8

2.30

Distance, Xb (m)

0.4

2.30

Distance, Xa (m)

0.8

Length, L (m)

6.670

Length, L (m)

6.70

15.33

User Input Footing Dimensions Width Left,b (m) Width Right,a (m) Area (m2)

15.41

Check User Input Footing Dimensions Allowable. Soil Pressure, qa (kPa)

Thickness, t (m) Effective depth, d(m)

1.200 1.112

Uniform upward pressure, qu (kN/m)

758.96

240.00

Maximum. Soil Pressure, qmax (kPa) Minimum. Soil Pressure, qmin (kPa) Check User Input Effective Depth Max. wide beam shear, Vw (kN)

1944.45

>

Wide beam shear strength, Vc1 (kN)

1091.61

O.K.

Max. punching shear, Vp (kN)

2625.75

>

Punching shear strength, Vc2 (kN)

1513.59

O.K.

Area of Steel Steel Diameter (mm)

36

for top reinforcement,

As(mm2)

1017.88

Steel Diameter (mm)

36

for bot reinforcement,

As(mm2)

1017.88

Details x

V (kN)

M (kN-m)

Rn

þmin

þactual

As (mm2)

s(mm)

0.000

0.00

-

-

0.0025

-

-

-

0.200

151.79

-

-

0.0025

-

-

-

0.229

0.00

17.887

0.02

0.0025

0.000058261

2780

366.14

0.600

-1916.13

-

-

0.0025

-

-

3.125

0.00

-2768.34

2.49

0.0025

5.675

1935.57

-

-

0.0025

-

-

-

6.042

0.00

-

-

0.0025

-

-

-

6.125

-436.40

145.04

0.13

0.0025

0.000474016

2780

366.14

6.700

0.00

-

-

0.0025

-

-

-

0.009790937 10887.5217

S= 93.49

S= 366.14

S= 366.14

93.49

DESIGN of COMBINED FOOTING (Axially Loaded) Project: CAMP JOHN HAY MANOR 2E INPUT MATERIALS: Concrete:

f'c Steel: fy Concrete Unit Weight: Concrete Cover : Soil Unit Weight. : Soil Brg. Cap : Main Bar: Temp. Bar :

Date: Mark:

= = = = = = = =

20.7 414 23.56 75 16 478 20 16

MPa MPa kN/m3 mm kN/m3 kPa mm ø mm ø

= = = = = = =

317.4 74.57 571 684.84 263.19 1406

Kn Kn Kn Kn Kn Kn

3/11/2016 9:20

CF-1

FOOTING LOADS: Col 1 :

Col 2 :

PDL PLL Pu PDL PLL Pu

DIMENSIONS:

column 1 column 2

thickness length width depth col thk col width col thk col width

= = = = = = = = = = = = = =

T L B H t b t b X1 X2 X3

A required A provided

1406.199 0.7 4.4 1.8 1.2 0.3 0.5 0.3 0.5 0.01 2.68 1.13 2.95 7.92

m m m m m m m m m mm2 mm2

SCHEMATIC DIAGRAMS : N.G.L.

note: proper computations must be done for x1 to x3 in order that the load resultant coincides w/ the center of gravit of the footing. If x1 or x3 is zero, input must be 0.01.

col 1

col 2 3/20

4/20

OUTPUT:

Pu SOIL PRESSURES: qnet qult Wushort Wulong Eff. Depth, dL Eff. Depth, dS Eff. Width,

= = = = = = =

MOMENTS: Along long direction: @center of col. 1 : between columns: @center of col. 2 : Along short direction: @ face of column:

453.886 249.66 781.22 449.39 565.00 555.00 1147.50

kPa kPa kN/m kN/m mm mm mm

Pu

Wu

= = =

0.03 -271.54 458.66

kN-m kN-m kN-m

=

165.03

kN-m

= = = =

4.49 -431.82 770.31 -501.07

kN kN kN kN

SHEARS: Along long direction: @ left Face of col1 @ right Face of col1 @ left Face of col2 @ right Face of col2

ACTUAL STRESSES vs. ALLOWABLE : V punching actual = Vpunching allowable = V beam actual = Vbeam allowable =

0.63 1.52 0.60 0.76

MPa MPa MPa MPa

safe against punching shear! safe against beam shear!

= Actual Soil Pressure: Ptotal / Areaactual actual ftg.wt. Ptotal = ftg.wt.+ Paxial

188.34

kN

Ptotal Total Weight = 1528.3 q Actual Soil Pressure = 192.97 actual qallow All. Soil Pressure = 478.00 Actual soil pressure is less than allowable; Safe!

kN kPa kPa

ADOPT:

REINFORCEMENTS: Along Long Direction: As1 = 3439.1304 mm2 As2 = 3439.1304 mm2 Temperature Bars: Along Short Direction: As3 = 2153.6413 mm2 Temperature Bars:

=

1.8 B

Provide Provide Provide Provide Provide

X X

4.4 L

X X

0.7 T

11 pcs -11 pcs -16 mm ø @

20 20 150

mm-ø mm-ø mm

7 pcs -16 mm ø @

20 150

mm-ø mm

combined footing

bottom bars top bars on center bottom bars on center 5/20

6/20

combined footing

@ columns b/n columns.

within Be

7/20

8/20

COMBINED FOOTING INPUT DATA: @ 4/B Concrete Strength, f'c Steel Yield Strength, fy Reduction factor,   Column size, b h owable Soil Pressure, Ps Unit Weight of Soil, SOIL Main Reinforcement,  FOOTING AREA: PDL = PLL = PU =

= = = = = = = = = =

650 517 1789

27.6 414 0.90 0.85 600 600 6.00 ### 16 20

MPa MPa (for flexure) (for shear) mm mm ksf kPa kN/m3 mm2

PDL = PLL = PU =

kN kN kN

PTOTAL = 1167 kN

1098 698 2724

kN kN kN

PTOTAL = 1796 kN

h = 2.0

m.

t = 0.6 m. Allowable qNET = Ps - (soil x h) - (concrete x t) = 241 kPa AREA = P/qNET = 12.3 m2 A = length x width L = 6.00 m W = 2.05 m say W = 5.00 m

THICKNESS: TRY t = ### mm de = ### mm check for punching shear: PTOTAL = 1796 kN

c+d= bo = 4(c +d) =

1805 7220

mm. mm.

qAVE = R/A = 98.77 kPa Vp = ### kN Vup = 2240.8 kN Vcp =

t

check for beam shear: dL = dAVE + /2 = 1215.0 mm.

### kN

Vup < Vcp safe for punching shear

1789

1.00

2724

9.225

1.30

354.63 kN/m 0.6

0.6

2050.00 354.63 0

0

-461.02 -1221.49

COMBINED FOOTING INPUT DATA: @ 4/B Concrete Strength, f'c Steel Yield Strength, fy Reduction factor,   Column size, b h owable Soil Pressure, Ps Unit Weight of Soil, SOIL Main Reinforcement,  FOOTING AREA: PDL = PLL = PU =

= = = = = = = = = =

650 517 1789

27.6 414 0.90 0.85 600 600 6.00 ### 16 20

MPa MPa (for flexure) (for shear) mm mm ksf kPa kN/m3 mm2

PDL = PLL = PU =

kN kN kN

PTOTAL = 1167 kN

1098 698 2724

kN kN kN

PTOTAL = 1796 kN

h = 2.0

m.

t = 0.6 m. Allowable qNET = Ps - (soil x h) - (concrete x t) = 241 kPa AREA = P/qNET = 12.3 m2 A = length x width L = 6.00 m W = 2.05 m say W = 5.00 m

THICKNESS: TRY t = ### mm de = ### mm check for punching shear: PTOTAL = 1796 kN

c+d= bo = 4(c +d) =

1805 7220

mm. mm.

qAVE = R/A = 98.77 kPa Vp = ### kN Vup = 2240.8 kN Vcp =

t

check for beam shear: dL = dAVE + /2 = 1215.0 mm.

### kN

Vup < Vcp safe for punching shear

1789

1.00

2724

9.225

1.30

354.63 kN/m 0.6

0.6

2050.00 354.63 0

0

-461.02 -1221.49

1237

COMBINED FOOTING crete Strength, f'c = 28 MPa l Yield Strength, fy = 414 MPa eduction factor,  =### (for flexure)  =### (for shear) Column size, b = 600 mm h = 600 mm e Soil Pressure, Ps =### ksf = 192 kPa t Weight of Soil, SOIL = 16 kN/m3 Reinforcement,  = 25 mm2 FOOTING AREA: PDL = ### kN PLL = ### kN PU = ### kN

PDL = ### kN PLL = ### kN PU = ### kN

PTOTAL = 824 kN

PTOTAL = 824 kN

2.50

###

552.10 0

h = ###m.

t = ###m.

Allowable qNET = Ps - (soil x h) - (concrete x t) =###kPa AREA = P/qNET = ## m2 A = length x width L =### m W =### m say W = 1.5 m

551

THICKNESS: TRY t =### mm de =### mm check for punching shear: PTOTAL = 824 kN

c+d= bo = 4(c +d) =

900 3600

mm. mm.

qAVE = R/A =

110 kPa Vp = 735.01 kN Vup = 1117.2 kN

Vcp =

t

check for beam shear: dL = dAVE + /2 = 312.5 mm.

1619.2 kN

Vup < Vcp safe for punching shear

kN

1237 kN

5.00

2.50

220.84 kN/m ###

552.10

0

-552.10 ###