column design

Column Design

COLUMN DESIGN

Dead 3.50 m

finishes 1.00 KN/m2 No of Stories = 4

Floors & roof column grid Lx = 5.000 m

3.50 m Ly = 5.000 m

Imposed

Floors 2.50 KN/m2 Beam b = 0.300 m

Roof 1.00 KN/m2 (One way only) h = 0.525 m

Partitions 1.00 KN/m2 3.50 m

Column x = 0.300 m

y = 0.300 m

Slab thickness = 0.175 m

5.00 m

Concrete density = 24 KN/m3

fy = 460 N/mm2

fcu = 25 N/mm2

Area corresponding to Column = 25.00 m2

Clear height

Dead Loads Ground Lox = 5.000 m

From slabs = 420.0 KN Loy = 5.350 m

From beams(if two way*2) = 50.4 KN Floors Lox = 2.975 m

From column = 30.1 KN Loy = 3.325 m

From finishes = 100.0 KN

Gk = 600.48 3.8.1.6.2

= Beam direction

Imposed Loads β = 0.75

From floors = 187.5 KN Other Direction

From roof = 25.0 KN β = 0.80 Ground

From partitions = 75.0 KN β = 0.85 Other

Qk = 287.50

Lox = 3.750 m ground

UDL n = 1300.67 KN Loy = 2.231 m other

Lox = 4.280 m ground

Design of Main steel Use 4 T 20 Loy = 2.826 m other

3.8.4.3 For short Column Resisting Axial Load Lex/h = 12.50 m ground < 15 Short

Ley/h = 7.44 m other < 15 Short

Eq 38 N = (0.4) fcu*Ac+(0.75) Asc*fy Lex/h = 14.27 m ground < 15 Short

Ley/h = 9.42 m other < 15 Short

Asc Provide = 1257.14 mm2

Ac = 88742.86 mm2

Eq 38 Ascrequire = 1197.80 mm2 > 1257.14

100As/Ac = 1.40 > 0.4 Table 3.27

Minimum Steel Ok

Short Column with Axial laod with Moments Concrete density = 24 KN/m3

fy = 460 N/mm2

N = 800 KN fcu = 25 N/mm2

M = 80 KNm 400 mm

N/bh = 6.67 For all cases

300 mm

(a) Major axis bending

b = 300

h = 400

4T 16

M/bh2 = 1.67

Chart 23 400 mm

100Asc/bh = 0.4

Asc = 480.00 mm2 300 mm

Use 4 T 16 Asc = 804.57 mm2

Design of links

3.12.7.1

Fror major axis bendind use T 16

Links 6 > 16/4 = 4 mm

Spacing 175 < 12*16 = 192 mm

(b) Minor axis bending

b = 400 4T 20

h = 300

400 mm

M/bh2 = 2.22

Chart 23

100Asc/bh = 0.8 300 mm

Asc = 960.00 mm2

Use 4 T 20 Asc = 1257.14 mm2

Design of links

3.12.7.1

Fror minor axis bendind use T 20

Links 6 > 20/4 = 5 mm

Spacing 225 < 12*20 = 240 mm

(C) Biaxial bending

3.8.4.5 Mx/h' = 228571.43 Eq 40 Mx' = Mx + βh'My/b'

Mx/b' = 320000.00 Eq 41 My' = My + βb'Mx/h'

h' = 350 400 mm

Mx/h' < Mx/b' Eq 41

Mx/h' > Mx/b' Eq 40

300 mm

Hence b' = 250 Table 3.25 Value of the coefficient β

Eq 41 My' = My + βb'Mx/h' N/(b*h*fcu) 0 0.1 0.2 0.3 0.4 0.5 >0.6

β 1 0.88 0.77 0.65 0.53 0.42 0.3

N/(b*h*fcu) = 0.267 0.2 0.3

β 0.77 0.7

From Table 3.24 β = 0.69 0.067

My' = 119.43 KNm

M/bh2 = 3.3

Chart 23

100Asc/bh = 1.7

Asc = 2040 mm2

use T Nos Area

32 0 0.0

25 4 1964.3

20 0 0.0

16 2 402.3 Each direction

Total Asprov 2366.6

Design of links

3.12.7.1


Links 8 > 16/4 = 4 mm

Spacing 175 < 12*16 = 192 mm

Check for shear

3.8.4.6 M/N = 0.149 < .75*h 0.225

Shear is not critical

Crack control

3.8.6 0.2.fcu.Ac < N

596 < 800 Crack check not required

Slender column le = 7200

3.8.1.3 Type of column = Le/h Concrete density = 24 KN/m3

3.8.3.3 = 7200/400 fy = 460 N/mm2

= 18 > 15 Slender

N = 800 KN fcu = 25 N/mm2

M2 = 80 KNm 400 mm

M1 = -40 KNm

300 mm

(a) Major axis bending

b = 300

h = 400

h/b = 1.33 < 3 Single axis bending

Bend about major axis

Design moments

3.8.3.2 eq 36 Mi = 0.4M1+0.6M2

Mi = 32 KNm

3.8.2.4 emin = 0.05*h

emin = 20 mm

Nemin = 16 KNm

Eq 34 βa = (1/2000)*(le/b')2

= 0.288

Eq 32 au = βa * K *h assume k = 1

= 0.115

Eq 35 Madd = N*au

= 92 KNm

Critical moment Mi + Madd = 124 KNm if K is reduced, Mi+Madd becomes < (M2) 80 KNm, hence M2 become criticals

Design of Reinforcements

Cover = 30 mm

Main bar diameter = 25 mm

Links bar diameter = 8 mm

d = 349.5

d/h = 0.87

N/bh = 6.67

M/bh2= 2.59

Chart 23 K = 0.9

Madd = 83 KNm

Mi + Madd = 115 KNm > 80

M/bh2= 2.4

Chart 23 K = 0.85

Madd = 78 KNm

Mi + Madd = 110 KNm > 300

M/bh2= 2.30

Chart 23 K = 0.85 Hence k = 0.85

Chart 23 100Asc/bh = 0.8

Asc = 960 mm2

use T Nos Area

32 0 0.0

25 0 0.0

20 4 1257

16 0 0.0

Total Asprov 1257.1

Design of links

3.12.7.1


Links 6 > bar dia/4 = 5 mm

Spacing 225 < 12*bar dia = 240 mm

Check for shear

3.8.4.6 M/N = 155 < .75*h 300

Shear is not critical

Crack control

3.8.6 0.2.fcu.Ac < N

594 < 800 Crack check not required

Table 3.11

0.50 0.75 1.00 1.50 2.00

100 2.00 2.00 2.00 1.86 1.63

150 2.00 2.00 1.98 1.69 1.49

156 2.00 2.00 1.96 1.66 1.47

200 2.00 1.95 1.76 1.51 1.35

250 1.90 1.70 1.55 1.34 1.20

288 1.68 1.50 1.38 1.21 1.09

300 1.60 1.44 1.33 1.16 1.06

M/bd2 0.96

0.75 1.00

259 250.00 1.70 1.55 1.57

288.00 1.50 1.38 1.40

F 1.53

Modification factor for tension reinforcement

M/bd2

fy = 250

fy = 460

Service Stress

3.00 4.00 5.00 6.00

1.36 1.19 1.08 1.01

1.25 1.11 1.01 0.94

1.24 1.10 1.00 0.94

1.14 1.02 0.94 0.88

1.04 0.94 0.87 0.82

0.95 0.87 0.82 0.78

0.93 0.85 0.80 0.76

Modification factor for tension reinforcement

M/bd2

Table 3.16 Shear force coefficient

Values of Ly/Lx

1.00 1.10 1.20 1.30 1.40 1.50 1.75

Interior panels

Continous Edge 0.33 0.36 0.39 0.41 0.43 0.45 0.48

One short edge discontinous

Continous Edge 0.36 0.39 0.42 0.44 0.45 0.47 0.5

Discontinous Edge - - - - - - -

One Long edge discontinous

Continous Edge 0.36 0.40 0.44 0.47 0.49 0.51 0.55

Discontinous Edge 0.24 0.27 0.29 0.31 0.32 0.34 0.36

Two adjacent edge discontinous

Continous Edge 0.40 0.44 0.47 0.50 0.52 0.54 0.57


Two short edge discontinous

Continous Edge 0.40 0.43 0.45 0.47 0.48 0.49 0.52

Discontinous Edge - - - - - - -

Two long edge discontinous

Continous Edge - - - - - - -


Type of panel and

location

Short span coefficients, βvx

2.00

0.50 0.33

0.52 0.36

- 0.24

0.59 0.36

0.38 -

0.60 0.40

0.40 0.26

0.54 -

- 0.26

- 0.4

0.47 -

Short span coefficients, βvx Long span

coefficients, βvy

for all Ly/Lx

Table 3.09 Value of Vc, Design concrete shear stress

125 150 175 200 225 250

N/mm2 N/mm2 N/mm2 N/mm2 N/mm2 N/mm2

< .15 0.45 0.43 0.41 0.40 0.39 0.38

0.25 0.53 0.51 0.49 0.47 0.46 0.45

0.50 0.67 0.64 0.62 0.60 0.58 0.56

0.75 0.77 0.73 0.71 0.68 0.66 0.65

1.00 0.84 0.81 0.78 0.75 0.73 0.71

1.50 0.97 0.92 0.89 0.86 0.83 0.81

2.00 1.06 1.02 0.98 0.95 0.92 0.89

>3.0 1.22 1.16 1.12 1.08 1.05 1.02

Depth 150

150 175

100As/bvd 0.3 0.25 0.51 0.49 0.51

0.50 0.64 0.62 0.64

Vc 0.54

100As/bvdEffective Depth (mm)

300 400 <

N/mm2 N/mm2

0.36 0.34

0.43 0.40

0.54 0.50

0.62 0.57

0.68 0.63

0.78 0.72

0.86 0.80

0.98 0.91

Effective Depth (mm)

column design

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