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Example 4.1 [Uni-axial Column Design] 1. Design the braced short column to sustain a design load of 1100 KN and a design moment of 160KNm which include all other effects .Use C25/30 and S460 class 1 works Take β€² = 0.1 and section 270 βˆ— 450 Solution Step 1- Material = 0.85 βˆ— 25 1.5 = 14.16667 = 460 1.15 = 400 Step 2-Determine the normalized axial and bending moment value = β„Ž = 1100 βˆ— 10 3 14.1667 βˆ— 270 βˆ— 450 = 0.639 = 2 = 160 βˆ— 10 6 14.1667 βˆ— 270 βˆ— 450 2 = 0.2065 Step 3-Using β€² = 0.1 read the mechanical steel ratio from uniaxial interaction chart for = 0.639 = 0.2065 From interaction chart = 0.3
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Page 1: Example 4.1 [Uni-axial Column Design] - · PDF fileExample 4.2 [Biaxial column design] Determine the longitudinal reinforcement for corner column of size 400*400 mm and the design

Example 4.1 [Uni-axial Column Design]

1. Design the braced short column to sustain a design load of 1100 KN and a design moment of

160KNm which include all other effects .Use C25/30 and S460 class 1 works

Take 𝑑′

𝐻= 0.1 and section 270 π‘šπ‘š βˆ— 450 π‘šπ‘š

Solution

Step 1- Material

𝑓𝑐𝑑 =0.85 βˆ— 25

1.5= 14.16667 π‘šπ‘π‘Ž

𝑓𝑦𝑑 =460

1.15= 400 π‘šπ‘π‘Ž

Step 2-Determine the normalized axial and bending moment value

𝑣𝑠𝑑 =𝑁𝑠𝑑

π‘“π‘π‘‘π‘β„Ž=

1100 βˆ— 103

14.1667 βˆ— 270 βˆ— 450= 0.639

πœ‡π‘ π‘‘ =π‘šπ‘ π‘‘

𝑓𝑐𝑑𝑏𝑑2=

160 βˆ— 106

14.1667 βˆ— 270 βˆ— 4502= 0.2065

Step 3-Using 𝑑′

𝐻= 0.1 read the mechanical steel ratio from uniaxial interaction chart for

𝑉𝑠𝑑 = 0.639 πœ‡π‘ π‘‘ = 0.2065

From interaction chart πœ” = 0.3

Page 2: Example 4.1 [Uni-axial Column Design] - · PDF fileExample 4.2 [Biaxial column design] Determine the longitudinal reinforcement for corner column of size 400*400 mm and the design

𝐴𝑠,π‘‘π‘œπ‘‘ =πœ”π‘“π‘π‘‘π‘π‘‘

𝑓𝑦𝑑=

0.3 βˆ— 14.166 βˆ— 270 βˆ— 450

400= 1290.937 π‘šπ‘š2

𝐴 =𝐴𝑠,π‘‘π‘œπ‘‘

2=

1290.937

2= 645.468 π‘šπ‘š2

Check with maximum and minimum reinforcement limit

𝐴𝑠,π‘šπ‘–π‘› = π‘šπ‘Žπ‘₯ {

0.1 𝑁𝐸𝐷

𝑓𝑦𝑑

0.002𝐴𝑐

= 275 π‘šπ‘š2 𝑂𝐾!

𝐴𝑠,π‘šπ‘Žπ‘₯ = 0.08 𝐴𝑐 = 0.08 βˆ— 270 βˆ— 450 = 𝑂𝐾!

Step 4- Detailing

π‘ˆπ‘ π‘’ 4βˆ…16 π‘œπ‘› π‘’π‘Žπ‘β„Ž π‘“π‘Žπ‘π‘’

Page 3: Example 4.1 [Uni-axial Column Design] - · PDF fileExample 4.2 [Biaxial column design] Determine the longitudinal reinforcement for corner column of size 400*400 mm and the design

Example 4.2 [Biaxial column design]

Determine the longitudinal reinforcement for corner column of size 400*400 mm and the design

factored moment and axial force of

𝑃 = 1360 𝐾𝑁 𝑀𝑠𝑑,β„Ž = 200 πΎπ‘π‘š 𝑀𝑠𝑑,𝑏 = 100 πΎπ‘π‘š

Use C25/30 and S460 class 1 work take β„Žβ€²

β„Ž=

𝑏′

𝑏= 0.1

Solution

Step 1- Material

𝑓𝑐𝑑 =0.85 βˆ— 25

1.5= 14.16667 π‘šπ‘π‘Ž

𝑓𝑦𝑑 =460

1.15= 400 π‘šπ‘π‘Ž

Step 2- Determine the normalized axial and bending moment value

𝑣𝑠𝑑 =𝑝

π‘“π‘π‘‘π‘β„Ž=

1360βˆ—103

14.1667βˆ—400βˆ—400= 0.6

πœ‡π‘ π‘‘,β„Ž =π‘šπ‘ π‘‘

𝑓𝑐𝑑𝑏𝑑2=

200 βˆ— 106

14.1667 βˆ— 400 βˆ— 4002= 0.2206

πœ‡π‘ π‘‘,𝑏 =π‘šπ‘ π‘‘

𝑓𝑐𝑑𝑑𝑏2=

100 βˆ— 106

14.1667 βˆ— 400 βˆ— 4002= 0.1103

Step 3- Find πœ” using 𝑑′

𝑑=

𝑏′

𝐡= 0.1 , 𝑉𝑠𝑑 = 0.6 ,

πœ‡π‘ π‘‘,β„Ž = 0.2206 ,

πœ‡π‘ π‘‘,𝑏 = 0.1103

From biaxial chart πœ” = 0.6

𝐴𝑠,π‘‘π‘œπ‘‘ =πœ”π‘“π‘π‘‘π‘π‘‘

𝑓𝑦𝑑=

0.6 βˆ— 14.166 βˆ— 400 βˆ— 400

400= 3400 π‘šπ‘š2

Check with maximum and minimum reinforcement limit

𝐴𝑠,π‘šπ‘–π‘› = π‘šπ‘Žπ‘₯ {

0.1 𝑁𝐸𝐷

𝑓𝑦𝑑

0.002𝐴𝑐

= 340 π‘šπ‘š2 𝑢𝑲!

𝐴𝑠,π‘šπ‘Žπ‘₯ = 0.08 𝐴𝑐 = 0.08 βˆ— 400 βˆ— 400 = 12800 𝑢𝑲!

Page 4: Example 4.1 [Uni-axial Column Design] - · PDF fileExample 4.2 [Biaxial column design] Determine the longitudinal reinforcement for corner column of size 400*400 mm and the design

Step 4- Detailing

𝑒𝑠𝑖𝑛𝑔 βˆ…24 𝑛 =3400

452.16= 7.52 π‘ π‘œ π‘ˆπ‘ π‘’ 8βˆ…24

Page 5: Example 4.1 [Uni-axial Column Design] - · PDF fileExample 4.2 [Biaxial column design] Determine the longitudinal reinforcement for corner column of size 400*400 mm and the design

Example 4.3 [Column]

Determine whether the column CD is slender or not, if it is subjected t loads shown below.

Consider the frame to be non-sway

Use C25/30 𝑓𝑐𝑑 = 14.1667 π‘šπ‘π‘Ž

Solution

Step 1- Slenderness limit

Ζ›π‘™π‘–π‘š = 20π΄π΅πΆβˆšπ‘›

⁄ π‘‘π‘Žπ‘˜π‘’ 𝐴 = 0.7 𝐡 = 1.1 𝐢 = 1.7 βˆ’ π‘Ÿπ‘š

Page 6: Example 4.1 [Uni-axial Column Design] - · PDF fileExample 4.2 [Biaxial column design] Determine the longitudinal reinforcement for corner column of size 400*400 mm and the design

π‘€β„Žπ‘’π‘Ÿπ‘’ π‘Ÿπ‘š =π‘š01

π‘š02=

βˆ’34.4

68.8= βˆ’0.5 𝐢 = 1.7 βˆ’ (βˆ’0.5) = 2.2

𝑛 =𝑁𝑒𝑑

𝐴𝑐𝑓𝑐𝑑=

516 βˆ— 103

14.1667 βˆ— 400 βˆ— 400= 0.227647

Ζ›π‘™π‘–π‘š =20 βˆ— 0.7 βˆ— 1.1 βˆ— 2.2

√0.227647= 71.0088

Step 2-Find the slenderness of the column

2.1 Effective length

For Braced member

𝑙0 = 0.5π‘™βˆš[1 +𝐾1

0.5 + 𝐾1] [1 +

𝐾2

0.5 + 𝐾2]

𝐾 =πΆπ‘œπ‘™π‘’π‘šπ‘› 𝑠𝑑𝑖𝑓𝑓𝑛𝑒𝑠𝑠

βˆ‘ π‘π‘’π‘Žπ‘š 𝑠𝑑𝑖𝑓𝑓𝑛𝑒𝑠𝑠

𝐾𝑖 =(𝐸𝐼

𝑙⁄ )π‘π‘œπ‘™π‘’π‘šπ‘›

2(2 𝐸𝐼𝑙⁄ )π‘π‘’π‘Žπ‘š

πΌπ‘π‘œπ‘™π‘’π‘šπ‘› =400 βˆ— 4003

12= 2133333333 π‘šπ‘š4

πΌπ‘π‘’π‘Žπ‘š =250 βˆ— 5003

12= 2604166667 π‘šπ‘š4

𝐾1 =

2133333333𝐸6

2(2 βˆ— 2604166667𝐸

6)

= 0.2048

For fixed restraint K=0 but in reality we cannot provide a fully fixed support so use 𝐾2 = 0.1

𝑙0 = 0.5 βˆ— 6000√[1 +0.2048

0.5 + 0.2048] [1 +

0.1

0.5 + 0.1] = 3736.7187 π‘šπ‘š

Ζ› =π‘™π‘œ

𝑖 𝑖 = √

𝐼

𝐴= √

2133333333

160000= 115.470 π‘šπ‘š

Ζ› =3736.7187

115.470= 32.361 π‘šπ‘š

Ζ› < Ζ›π‘™π‘–π‘š π‘†β„Žπ‘œπ‘Ÿπ‘‘ π‘π‘œπ‘™π‘’π‘šπ‘›

Page 7: Example 4.1 [Uni-axial Column Design] - · PDF fileExample 4.2 [Biaxial column design] Determine the longitudinal reinforcement for corner column of size 400*400 mm and the design

Example 4.4 [Column Design]

Design the braced column to resist an axial load of 950 KN and a moment of Msd =115 KNM at

the top and Msd =-95 KNM at the bottom as shown below .length of the column is 5.5 m and

cross-section of 300*300 mm use C25/30 and S460 take Le=0.66L

.

Solution

Step 1- Material

𝑓𝑐𝑑 =0.85 βˆ— 25

1.5= 14.16667 π‘šπ‘π‘Ž

𝑓𝑦𝑑 =460

1.15= 400 π‘šπ‘π‘Ž

Step 2- Check slenderness limit

Ζ›π‘™π‘–π‘š = 20π΄π΅πΆβˆšπ‘›

⁄ π‘‘π‘Žπ‘˜π‘’ 𝐴 = 0.7 𝐡 = 1.1 𝐢 = 1.7 βˆ’ π‘Ÿπ‘š

π‘€β„Žπ‘’π‘Ÿπ‘’ π‘Ÿπ‘š =π‘š01

π‘š02=

βˆ’95

115= βˆ’0.826 𝐢 = 1.7 βˆ’ (βˆ’0.826) = 2.526

𝑛 =𝑁𝑒𝑑

𝐴𝑐𝑓𝑐𝑑=

950 βˆ— 103

14.1667 βˆ— 300 βˆ— 300= 0.745

Ζ›π‘™π‘–π‘š =20 βˆ— 0.7 βˆ— 1.1 βˆ— 2.526

√0.745= 45.066

Step 3-Slenderess

Ζ› =π‘™π‘œ

𝑖 𝑖 = √

𝐼

𝐴= √

675000000

90000= 86.6025 π‘šπ‘š

Page 8: Example 4.1 [Uni-axial Column Design] - · PDF fileExample 4.2 [Biaxial column design] Determine the longitudinal reinforcement for corner column of size 400*400 mm and the design

Ζ› =0.66 βˆ— 5500

86.6025= 41.915 π‘šπ‘š

Ζ› < Ζ›π‘™π‘–π‘š 𝑺𝒉𝒐𝒓𝒕 π’„π’π’π’–π’Žπ’ π’π’†π’ˆπ’†π’π’†π’„π’• 𝒔𝒆𝒄𝒐𝒏𝒅 𝒐𝒓𝒅𝒆𝒓 𝒆𝒇𝒇𝒆𝒄𝒕

Step 4- accidental eccentricity

π‘’π‘Ž =π‘™π‘œ

400=

3630

400= 9.075 π‘šπ‘š

Step 5- Equivalent first order eccentricity

𝑒𝑒 = π‘šπ‘Žπ‘₯ {0.6𝑒02 + 0.4 𝑒01

0.4𝑒02

𝑒02 =𝑀02

𝑁𝑠𝑑=

115 βˆ— 106

950 βˆ— 103= 121.052 π‘šπ‘š

𝑒01 =𝑀01

𝑁𝑠𝑑=

95 βˆ— 106

950 βˆ— 103= 100 π‘šπ‘š

𝑒𝑒 = π‘šπ‘Žπ‘₯ {0.6𝑒02 + 0.4 𝑒01

0.4𝑒02 = 48.4208 mm

π‘’π‘‘π‘œπ‘‘ = π‘’π‘œ + 𝑒𝑒 + 𝑒02 = 9.075 + 48.4208 + 0 = 57.4958 π‘šπ‘š

π‘β„Žπ‘’π‘π‘˜ π‘€π‘–π‘‘β„Ž 𝑒 = 𝑒02 + π‘’π‘Ž = 121.052 + 9.075 = 130.127 π‘šπ‘š

π‘†π‘œ π‘‘π‘Žπ‘˜π‘’ π‘’π‘‘π‘œπ‘‘ = 130.127 π‘šπ‘š

Step 6- Design

𝑁𝑠𝑑 = 950 𝐾𝑁 𝑀𝑠𝑑 = 𝑁𝑠𝑑 βˆ— π‘’π‘‘π‘œπ‘‘ = 123.62 πΎπ‘π‘š

𝑣𝑠𝑑 =𝑝

π‘“π‘π‘‘π‘β„Ž=

950 βˆ— 103

14.1667 βˆ— 300 βˆ— 300= 0.745

πœ‡π‘ π‘‘ =π‘šπ‘ π‘‘

𝑓𝑐𝑑𝑏𝑑2=

123.62 βˆ— 106

14.1667 βˆ— 300 βˆ— 3002= 0.3232

Using 𝑑′

𝑑= 0.15 read the mechanical steel ratio from uniaxial interaction chart for

𝑉𝑠𝑑 = 0.745

πœ‡π‘ π‘‘ = 0.3232

πœ” = 0.79

𝐴𝑠,π‘‘π‘œπ‘‘ =πœ”π‘“π‘π‘‘π‘π‘‘

𝑓𝑦𝑑=

0.79 βˆ— 14.166 βˆ— 300 βˆ— 300

400= 2518.125 π‘šπ‘š2

𝐴 =𝐴𝑠,π‘‘π‘œπ‘‘

2=

2518.125

2= 1259.0625 π‘šπ‘š2

Page 9: Example 4.1 [Uni-axial Column Design] - · PDF fileExample 4.2 [Biaxial column design] Determine the longitudinal reinforcement for corner column of size 400*400 mm and the design

Check with maximum and minimum reinforcement limit

𝐴𝑠,π‘šπ‘–π‘› = π‘šπ‘Žπ‘₯ {

0.1 𝑁𝐸𝐷

𝑓𝑦𝑑

0.002𝐴𝑐

= 237.5 π‘šπ‘š2 𝑂𝐾!

𝐴𝑠,π‘šπ‘Žπ‘₯ = 0.08 𝐴𝑐 = 0.08 βˆ— 300 βˆ— 300 = 7200 π‘šπ‘š2 𝑢𝑲!

Using βˆ…20 π‘π‘Ÿπ‘œπ‘£π‘–π‘‘π‘’ 4βˆ…20 π‘œπ‘› π‘’π‘Žπ‘β„Ž π‘“π‘Žπ‘π‘’

Step 7- Detailing

Page 10: Example 4.1 [Uni-axial Column Design] - · PDF fileExample 4.2 [Biaxial column design] Determine the longitudinal reinforcement for corner column of size 400*400 mm and the design

Example 4.5 [Column]

Design the braced column if it is subjected to the following loading .the column has total length

of 6 m. Le=0.7L

Use C25/30 and S460

If the column is slender .compute the total design moment using

a) Nominal curvature

b) Nominal stiffness

Use 400*400 mm section 𝑑′

𝑑= 0.1 𝑒𝑠𝑒 βˆ…(∞, π‘‘π‘œ) = 2

Solution

Step 1. Material data

𝑓𝑐𝑑 =0.85 βˆ— 25

1.5= 14.16667 π‘šπ‘π‘Ž

𝑓𝑦𝑑 =460

1.15= 400 π‘šπ‘π‘Ž

πΈπ‘π‘š = 30 πΊπ‘π‘Ž

𝐸𝑠 = 200 πΊπ‘π‘Ž

Step 2- Check slenderness limit

Ζ›π‘™π‘–π‘š = 20π΄π΅πΆβˆšπ‘›

⁄ π‘‘π‘Žπ‘˜π‘’ 𝐴 = 0.7 𝐡 = 1.1 𝐢 = 1.7 βˆ’ π‘Ÿπ‘š

Page 11: Example 4.1 [Uni-axial Column Design] - · PDF fileExample 4.2 [Biaxial column design] Determine the longitudinal reinforcement for corner column of size 400*400 mm and the design

π‘€β„Žπ‘’π‘Ÿπ‘’ π‘Ÿπ‘š =π‘š01

π‘š02=

140

140= 1 𝐢 = 1.7 βˆ’ (1) = 0.7

𝑛 =𝑁𝑒𝑑

𝐴𝑐𝑓𝑐𝑑=

1650 βˆ— 103

14.1667 βˆ— 400 βˆ— 400= 0.72794

Ζ›π‘™π‘–π‘š =20 βˆ— 0.7 βˆ— 1.1 βˆ— 0.7

√0.72794= 12.63487

Step 3-slenderess

Ζ› =π‘™π‘œ

𝑖 𝑖 = √

𝐼

𝐴= √

2133333333

160000= 115.470 π‘šπ‘š

Ζ› =0.7 βˆ— 6000

115.470= 36.373 π‘šπ‘š

Ζ› > Ζ›π‘™π‘–π‘š 𝑺𝒍𝒆𝒏𝒅𝒆𝒓 π’„π’π’π’–π’Žπ’ π’„π’π’π’”π’Šπ’…π’†π’“ 𝒔𝒆𝒄𝒐𝒏𝒅 𝒐𝒓𝒅𝒆𝒓 𝒆𝒇𝒇𝒆𝒄𝒕

Step 4- accidental eccentricity

π‘’π‘Ž =π‘™π‘œ

400=

4200

400= 10.5 π‘šπ‘š

Step 5- Equivalent first order eccentricity

𝑒𝑒 = π‘šπ‘Žπ‘₯ {0.6𝑒02 + 0.4 𝑒01

0.4𝑒02

𝑒02 =𝑀02

𝑁𝑠𝑑=

140 βˆ— 106

1650 βˆ— 103= 84.848 π‘šπ‘š

𝑒01 =𝑀01

𝑁𝑠𝑑=

140 βˆ— 106

1650 βˆ— 103= 84.848 π‘šπ‘š

𝑒𝑒 = π‘šπ‘Žπ‘₯ {0.6𝑒02 + 0.4 𝑒01

0.4𝑒02 = 84.848 mm

Step 6- Calculate the second order moment

a) Using Nominal curvature method

𝑒2 =1

π‘Ÿπ‘™π‘œ

2

𝐢⁄ π‘ͺ = 𝟏𝟎 𝑭𝒐𝒓 𝒄𝒐𝒏𝒔𝒕𝒂𝒏𝒕 𝒄𝒓𝒐𝒔𝒔 βˆ’ π’”π’†π’„π’•π’Šπ’π’

1

π‘Ÿ= πΎπ‘ŸπΎβˆ…

1

π‘Ÿπ‘œ πΎβˆ… = 1 + π›½βˆ…π‘’π‘“π‘“

βˆ…π‘’π‘“π‘“ = 0 𝑖𝑓 {

βˆ…(∞, π‘‘π‘œ) ≀ 2 𝑢𝑲 Ζ› ≀ 75 𝑢𝑲 π‘€π‘œπ‘’π‘‘

𝑁𝑒𝑑β‰₯ β„Ž 𝑡𝒐𝒕 𝑢𝑲

Page 12: Example 4.1 [Uni-axial Column Design] - · PDF fileExample 4.2 [Biaxial column design] Determine the longitudinal reinforcement for corner column of size 400*400 mm and the design

βˆ…π‘’π‘“π‘“ = βˆ…(∞, π‘‘π‘œ)π‘€π‘œπ‘’π‘žπ‘

π‘€π‘œπ‘’π‘‘

π‘€β„Žπ‘’π‘Ÿπ‘’ π‘€π‘œπ‘’π‘žπ‘ = π‘“π‘–π‘Ÿπ‘ π‘‘ π‘œπ‘Ÿπ‘‘π‘’π‘Ÿ π‘šπ‘œπ‘šπ‘’π‘›π‘‘ 𝑖 π‘›π‘žπ‘’π‘Žπ‘ π‘– βˆ’ π‘π‘’π‘Ÿπ‘šπ‘Žπ‘›π‘’π‘›π‘‘ π‘™π‘œπ‘Žπ‘‘(𝑆𝐿𝑆)

π‘€π‘œπ‘’π‘‘ = πΉπ‘–π‘Ÿπ‘ π‘‘ π‘œπ‘Ÿπ‘‘π‘’π‘Ÿ π‘šπ‘œπ‘šπ‘’π‘›π‘‘ 𝑖𝑛 𝑑𝑒𝑠𝑖𝑔𝑛 π‘™π‘œπ‘Žπ‘‘ π‘π‘œπ‘šπ‘π‘–π‘›π‘Žπ‘‘π‘–π‘œπ‘› (π‘ˆπΏπ‘†)

βˆ…π‘’π‘“π‘“ = βˆ…(∞, π‘‘π‘œ)π‘€π‘œπ‘’π‘žπ‘

π‘€π‘œπ‘’π‘‘= 2 βˆ—

70

140= 1

𝛽 = 0.35 +π‘“π‘π‘˜

200⁄ βˆ’ Ζ›

150⁄ = 0.35 + 25200⁄ βˆ’ 36.375

150⁄ = 0.2325

πΎβˆ… = 1 + π›½βˆ…π‘’π‘“π‘“ = 1 + 0.2325 βˆ— 1 = 1.2325

1

π‘Ÿπ‘œ=

πœ€π‘¦π‘‘

0.45𝑑=

2 βˆ— 10βˆ’3

360= 123456 βˆ— 10βˆ’5 𝑑 = 𝑒𝑓𝑓𝑒𝑐𝑑𝑖𝑣𝑒 π‘‘π‘’π‘π‘‘β„Ž

πΎπ‘Ÿ =(𝑛𝑒 βˆ’ 𝑛)

(𝑛𝑒 βˆ’ π‘›π‘π‘Žπ‘™) 𝑛𝑒 = 1 + πœ” 𝑛 =

𝑁𝑒𝑑

𝐴𝑐𝑓𝑐𝑑=

1650 βˆ— 103

14.166 βˆ— 4002

= 0.72974 π‘›π‘π‘Žπ‘™ = 0.4

For first iteration take π’†πŸ = 𝟎

π‘’π‘‘π‘œπ‘‘ = π‘’π‘œ + 𝑒𝑒 + 𝑒02 = 10.5 + 84.848 + 0 = 95.348 π‘šπ‘š

𝑁𝑠𝑑 = 1650 𝐾𝑁 𝑀𝑠𝑑 = 𝑁𝑠𝑑 βˆ— π‘’π‘‘π‘œπ‘‘ = 157.3242 πΎπ‘π‘š

𝑣𝑠𝑑 =𝑁𝑠𝑑

π‘“π‘π‘‘π‘β„Ž=

1650 βˆ— 103

14.1667 βˆ— 400 βˆ— 400= 0.72794

πœ‡π‘ π‘‘ =π‘šπ‘ π‘‘

𝑓𝑐𝑑𝑏𝑑2=

157.3242 βˆ— 106

14.1667 βˆ— 400 βˆ— 4002= 0.17352

π‘ˆπ‘ π‘–π‘›π‘” 𝑣𝑠𝑑 = 0.72794 πœ‡π‘ π‘‘ = 0.1752 𝑑′

𝑑= 0.1 πœ” = 0.25

So

𝑛𝑒 = 1 + πœ” = 1.25 πΎπ‘Ÿ =(𝑛𝑒 βˆ’ 𝑛)

(𝑛𝑒 βˆ’ π‘›π‘π‘Žπ‘™)=

(1.25 βˆ’ 0.72794)

(1.25 βˆ’ 0.4)= 0.614

1

π‘Ÿ= 0.614 βˆ— 1.2325 βˆ— 1.23456 βˆ— 10βˆ’5 = 9.3456 βˆ— 10βˆ’6

𝑒2 =1

π‘Ÿ42002

10⁄ = 16.485 π‘šπ‘š

For Second iteration take π’†πŸ = πŸπŸ”. πŸ’πŸ–πŸ“ π’Žπ’Ž

π‘’π‘‘π‘œπ‘‘ = π‘’π‘œ + 𝑒𝑒 + 𝑒02 = 10.5 + 84.848 + 16.485 = 111.833 π‘šπ‘š

𝑁𝑠𝑑 = 1650 𝐾𝑁 𝑀𝑠𝑑 = 𝑁𝑠𝑑 βˆ— π‘’π‘‘π‘œπ‘‘ = 184.525 πΎπ‘π‘š

π‘ˆπ‘ π‘–π‘›π‘” 𝑣𝑠𝑑 = 0.72794 π‘Žπ‘›π‘‘ πœ‡π‘ π‘‘ = 0.2035 πœ” = 0.35

𝑛𝑒 = 1 + πœ” = 1.35 πΎπ‘Ÿ =(𝑛𝑒 βˆ’ 𝑛)

(𝑛𝑒 βˆ’ π‘›π‘π‘Žπ‘™)=

(1.35 βˆ’ 0.72794)

(1.35 βˆ’ 0.4)= 0.6548

1

π‘Ÿ= 0.6548 βˆ— 1.2325 βˆ— 1.23456 βˆ— 10βˆ’5 = 9.9634 βˆ— 10βˆ’6

Page 13: Example 4.1 [Uni-axial Column Design] - · PDF fileExample 4.2 [Biaxial column design] Determine the longitudinal reinforcement for corner column of size 400*400 mm and the design

𝑒2 =1

π‘Ÿ42002

10⁄ = 17.575 π‘šπ‘š

For their iteration take π’†πŸ = πŸπŸ•. πŸ“πŸ•πŸ“ π’Žπ’Ž

π‘’π‘‘π‘œπ‘‘ = π‘’π‘œ + 𝑒𝑒 + 𝑒02 = 10.5 + 84.848 + 17.575 = 112.923 π‘šπ‘š

𝑁𝑠𝑑 = 1650 𝐾𝑁 𝑀𝑠𝑑 = 𝑁𝑠𝑑 βˆ— π‘’π‘‘π‘œπ‘‘ = 186.323 πΎπ‘π‘š

π‘ˆπ‘ π‘–π‘›π‘” 𝑣𝑠𝑑 = 0.72794 π‘Žπ‘›π‘‘ πœ‡π‘ π‘‘ = 0.2055 πœ” = 0.35

The iteration converges with similar mechanical steel ratio 𝝎 = 𝟎. πŸ‘πŸ“ .

𝐴𝑠,π‘‘π‘œπ‘‘ =πœ”π‘“π‘π‘‘π‘π‘‘

𝑓𝑦𝑑=

0.35 βˆ— 14.166 βˆ— 400 βˆ— 400

400= 1983.33 π‘šπ‘š2

𝐴 =𝐴𝑠,π‘‘π‘œπ‘‘

2=

1983.33

2= 991.666 π‘šπ‘š2

Check with maximum and minimum reinforcement limit

𝐴𝑠,π‘šπ‘–π‘› = π‘šπ‘Žπ‘₯ {

0.1 𝑁𝐸𝐷

𝑓𝑦𝑑

0.002𝐴𝑐

= 412.5 π‘šπ‘š2 𝑢𝑲!

𝐴𝑠,π‘šπ‘Žπ‘₯ = 0.08 𝐴𝑐 = 0.08 βˆ— 400 βˆ— 400 = 12800 π‘šπ‘š2 𝑢𝑲!

Using βˆ…πŸπŸ” π’‘π’“π’π’—π’Šπ’…π’† πŸ“βˆ…πŸπŸ” 𝒐𝒏 𝒆𝒂𝒄𝒉 𝒇𝒂𝒄𝒆

.

b) Using Nominal stiffness method

𝐸𝐼 = 𝐾𝑐𝐸𝑐𝑑𝐼𝑐 + 𝐾𝑠𝐸𝑠𝐼𝑠

𝐸𝑐𝑑 =πΈπ‘π‘š

𝛾𝑐𝑒=

30

1.2= 25 πΊπ‘π‘Ž

Initially let us assume 𝝆 β‰₯ 𝟎. 𝟎𝟏 𝒕𝒐 𝒖𝒔𝒆 𝒕𝒉𝒆 𝐬𝐒𝐦𝐩π₯𝐒𝐟𝐒𝐞𝐝 π’Žπ’†π’•π’‰π’π’…

𝐾𝑠 = 0 𝐾𝑐 = 0.31 + 0.5βˆ…π‘’π‘“π‘“

⁄

Page 14: Example 4.1 [Uni-axial Column Design] - · PDF fileExample 4.2 [Biaxial column design] Determine the longitudinal reinforcement for corner column of size 400*400 mm and the design

βˆ…π‘’π‘“π‘“ = 1 𝐾𝑐 = 0.2

𝐼𝑐 =π‘β„Ž3

12= 2133333333 π‘šπ‘š4

𝐸𝐼 = 𝐾𝑐𝐸𝑐𝑑𝐼𝑐 + 𝐾𝑠𝐸𝑠𝐼𝑠 = 0.2 βˆ— 25 βˆ— 103 βˆ— 2133333333 = 1.06667 βˆ— 1013

𝑁𝑏 =П2𝐸𝐼

π‘™π‘œ2 =

П2 βˆ— 1.06667 βˆ— 1013

42002= 5968.01475 𝐾𝑁

Nb= Buckling load based on nominal stiffness

Design moment 𝑀𝑒𝑑 = π‘€π‘œπ‘’π‘‘ [1 +𝛽

(𝑁𝑏

𝑁𝑒𝑑⁄ )βˆ’1

]

𝛽 = П2π‘π‘œ

⁄

π‘π‘œ = 8

π‘€π‘œπ‘’π‘‘ = 140 πΎπ‘π‘š

𝑀𝑒𝑑 = π‘€π‘œπ‘’π‘‘ [1 +𝛽

(𝑁𝑏

𝑁𝑒𝑑⁄ ) βˆ’ 1

] = 140 βˆ— [1 +1.2337

(5968.014751650⁄ ) βˆ’ 1

]

= 205.999 πΎπ‘π‘š

For first iteration neglecting accidental eccentricity

𝑣𝑠𝑑 =𝑁𝑠𝑑

π‘“π‘π‘‘π‘β„Ž=

1650 βˆ— 103

14.1667 βˆ— 400 βˆ— 400= 0.72794

πœ‡π‘ π‘‘ =π‘šπ‘ π‘‘

𝑓𝑐𝑑𝑏𝑑2=

205.999 βˆ— 106

14.1667 βˆ— 400 βˆ— 4002= 0.2272

π‘ˆπ‘ π‘–π‘›π‘” 𝑣𝑠𝑑 = 0.72794 πœ‡π‘ π‘‘ = 0.2272 𝑑′

𝑑= 0.1 πœ” = 0.4

𝐴𝑠,π‘‘π‘œπ‘‘ =πœ”π‘“π‘π‘‘π‘π‘‘

𝑓𝑦𝑑=

0.4 βˆ— 14.166 βˆ— 400 βˆ— 400

400= 2266.666 π‘šπ‘š2

𝐴 =𝐴𝑠,π‘‘π‘œπ‘‘

2=

2266.666

2= 1133.333 π‘šπ‘š2

𝜌 =𝐴𝑠

𝑏𝑑=

1133.333

400 βˆ— 360= 7.870 βˆ— 10βˆ’3 𝜌 < 0.01

We cannot use the simplified method

π‘“π‘œπ‘Ÿ 𝜌 > 0.002 𝐾𝑠 = 1

𝐾𝑐 =𝐾1𝐾2

(1 + βˆ…π‘’π‘“π‘“)⁄

𝐾1 = βˆšπ‘“π‘π‘˜20

⁄ = 1.11803

Page 15: Example 4.1 [Uni-axial Column Design] - · PDF fileExample 4.2 [Biaxial column design] Determine the longitudinal reinforcement for corner column of size 400*400 mm and the design

𝐾2 = 𝑛ƛ

170≀ 0.2

𝑛 =𝑁𝑒𝑑

𝐴𝑐𝑓𝑐𝑑= 0.72794

𝐾2 = 0.2 π‘†π‘œ 𝐾𝑐 = 0.111803

𝐼𝑐 =π‘β„Ž3

12= 2133333333 π‘šπ‘š4

𝐼𝑠 = 2 βˆ— [1133.333(360 βˆ’ 200)2] = 58026666.67 π‘šπ‘š2

𝐸𝐼 = 𝐾𝑐𝐸𝑐𝑑𝐼𝑐 + 𝐾𝑠𝐸𝑠𝐼𝑠

= 0.111803 βˆ— 25 βˆ— 103 βˆ— 2133333333 + 1 βˆ— 200 βˆ— 103

βˆ— 58026666.6

𝐸𝐼 = 1.756816 βˆ— 1013

𝑁𝑏 =П2𝐸𝐼

π‘™π‘œ2 =

П2 βˆ— 1.756816 βˆ— 1013

42002= 9829.40982 𝐾𝑁

𝑀𝑒𝑑 = π‘€π‘œπ‘’π‘‘ [1 +𝛽

(𝑁𝑏

𝑁𝑒𝑑⁄ ) βˆ’ 1

] = 140 βˆ— [1 +1.2337

(9829.409821650⁄ ) βˆ’ 1

]

= 174.842 πΎπ‘π‘š

Design moment including accidental eccentricity is given by

𝑀 = 174.842 + 1650 βˆ— (10.5

1000) = 192.167 𝐾𝑁𝑀

𝑣𝑠𝑑 =𝑁𝑠𝑑

π‘“π‘π‘‘π‘β„Ž=

1650 βˆ— 103

14.1667 βˆ— 400 βˆ— 400= 0.72794

πœ‡π‘ π‘‘ =π‘šπ‘ π‘‘

𝑓𝑐𝑑𝑏𝑑2=

192.167 βˆ— 106

14.1667 βˆ— 400 βˆ— 4002= 0.212

π‘ˆπ‘ π‘–π‘›π‘” 𝑣𝑠𝑑 = 0.72794 πœ‡π‘ π‘‘ = 0.212 𝑑′

𝑑= 0.1 πœ” = 0.35

𝐴𝑠,π‘‘π‘œπ‘‘ =πœ”π‘“π‘π‘‘π‘π‘‘

𝑓𝑦𝑑=

0.35 βˆ— 14.166 βˆ— 400 βˆ— 400

400= 1983.333 π‘šπ‘š2

𝐴 =𝐴𝑠,π‘‘π‘œπ‘‘

2=

1983.33

2= 991.666 π‘šπ‘š2

𝜌 =𝐴𝑠

𝑏𝑑=

991.666

400 βˆ— 360= 6.886 βˆ— 10βˆ’3 𝜌 > 0.002

Second Iteration

Page 16: Example 4.1 [Uni-axial Column Design] - · PDF fileExample 4.2 [Biaxial column design] Determine the longitudinal reinforcement for corner column of size 400*400 mm and the design

𝐼𝑐 =π‘β„Ž3

12= 2133333333 π‘šπ‘š4

𝐼𝑠 = 2 βˆ— [991.666(360 βˆ’ 200)2] = 50773333.33 π‘šπ‘š2

𝐸𝐼 = 𝐾𝑐𝐸𝑐𝑑𝐼𝑐 + 𝐾𝑠𝐸𝑠𝐼𝑠

= 0.111803 βˆ— 25 βˆ— 103 βˆ— 2133333333 + 1 βˆ— 200 βˆ— 103

βˆ— 50773333.3

𝐸𝐼 = 1.611749 βˆ— 1013

𝑁𝑏 =П2𝐸𝐼

π‘™π‘œ2 =

П2 βˆ— 1.611749 βˆ— 1013

42002= 9017.7598 𝐾𝑁

𝑀𝑒𝑑 = π‘€π‘œπ‘’π‘‘ [1 +𝛽

(𝑁𝑏

𝑁𝑒𝑑⁄ ) βˆ’ 1

] = 140 βˆ— [1 +1.2337

(9017.75981650⁄ ) βˆ’ 1

]

= πŸπŸ•πŸ–. πŸ”πŸ•πŸ— π‘²π‘΅π’Ž

Design moment including accidental eccentricity is given by

𝑀 = 178.679 + 1650 βˆ— (10.5

1000) = 196.004 𝐾𝑁𝑀

𝑣𝑠𝑑 =𝑁𝑠𝑑

π‘“π‘π‘‘π‘β„Ž=

1650 βˆ— 103

14.1667 βˆ— 400 βˆ— 400= 0.72794

πœ‡π‘ π‘‘ =π‘šπ‘ π‘‘

𝑓𝑐𝑑𝑏𝑑2=

196.004 βˆ— 106

14.1667 βˆ— 400 βˆ— 4002= 0.216

π‘ˆπ‘ π‘–π‘›π‘” 𝑣𝑠𝑑 = 0.72794 πœ‡π‘ π‘‘ = 0.216 𝑑′

𝑑= 0.1 πœ” = 0.35

The iteration converges with similar mechanical steel ratio πœ” = 0.35 .

𝐴𝑠,π‘‘π‘œπ‘‘ =πœ”π‘“π‘π‘‘π‘π‘‘

𝑓𝑦𝑑=

0.35 βˆ— 14.166 βˆ— 400 βˆ— 400

400= 1983.33 π‘šπ‘š2

𝐴 =𝐴𝑠,π‘‘π‘œπ‘‘

2=

1983.33

2= 991.666 π‘šπ‘š2

Check with maximum and minimum reinforcement limit

𝐴𝑠,π‘šπ‘–π‘› = π‘šπ‘Žπ‘₯ {

0.1 𝑁𝐸𝐷

𝑓𝑦𝑑

0.002𝐴𝑐

= 412.5 π‘šπ‘š2 𝑢𝑲!

𝐴𝑠,π‘šπ‘Žπ‘₯ = 0.08 𝐴𝑐 = 0.08 βˆ— 400 βˆ— 400 = 12800 π‘šπ‘š2 𝑢𝑲!

Using βˆ…πŸπŸ” π’‘π’“π’π’—π’Šπ’…π’† πŸ“βˆ…πŸπŸ” 𝒐𝒏 𝒆𝒂𝒄𝒉 𝒇𝒂𝒄𝒆

Step 7- Detailing

Page 17: Example 4.1 [Uni-axial Column Design] - · PDF fileExample 4.2 [Biaxial column design] Determine the longitudinal reinforcement for corner column of size 400*400 mm and the design

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