Symbols

Ac = Reinforced concrete column cross-section area
fcd = Concrete design compressive strength
Nd = Axial force


  • According to TS 500 7.4.1, the cross section width should be minimum 250 mm in rectangular columns and the maximum normal force that the columns can bear under increased loads should meet the condition Nd ≤ 0.9fcdAc .

  • Depending on the chosen slab thickness, the load coverage areas of the columns will be calculated as shown, and the normal forces occurring in the columns under increased vertical loads will be determined.

  • There are 3 types of load areas as shown in the figure below. These calculations will be shown for Type1 only.

At Roof Story:

  • Loads from dead loads to the column;

  1. From the own weight of the slab: 8 m * 8 m * 0.27 m * 25 kN / m 3 = 432 kN

  2. From the coating load: 8 m * 8 m * 4 kN / m 2 = 256 kN

  3. From the column's own weight (assumed 80 * 80): 0.8 m * 0.8 m * 3.5 m * 25 kN / m 3 = 56 kN

Total G = 432 + 256 + 56 = 744 kN

  • From live load: 8 m * 8 m * 1.0 kN / m2 = 64 kN

Q = 64 kN

Office Stories:

  • Loads from dead loads to the column;

  1. From the own weight of the slab: 8 m * 8 m * 0.27 m * 25 kN / m 3 = 432 kN

  2. From the coating load: 8 m * 8 m * 1.5 kN / m 2 = 96 kN

  3. From the column's own weight (assumed 80 * 80): 0.8 m * 0.8 m * 3.5 m * 25 kN / m 3 = 56 kN

Total G = 432 + 96 + 56 = 584 kN

  • From live load: 8 m * 8 m * 2.0 kN / m2 = 128 kN

Q = 128 kN

In Basement Stories:

  • Loads from dead loads to the column;

  1. From the own weight of the slab: 8 m * 8 m * 0.27 m * 25 kN / m 3 = 432 kN

  2. From the coating load: 8 m * 8 m * 0.5 kN / m 2 = 32 kN

  3. From the column's own weight (assumed 80 * 80): 1 m * 1 m * 3.5 m * 25 kN / m 3 = 88 kN

Total G = 432 + 32 + 88 = 552 kN

  • From live load: 8 m * 8 m * 5.0 kN / m2 = 320 kN

Q = 320 kN

Material Information

Selected Column Front Dimensions

Story

Story elevation

G + Q

1.4G + 1.6Q

Ac≥ N 1.4G + 1.6Q /0.9f cd

Front size selected

12th story

43

808

1144

0.05

60/60

11th story

39.5

1520

2166

0.1

60/60

10th story

36

2232

3189

0.15

60/60

9th story

32.5

2944

4211

0.2

60/60

8th story

29

3656

5234

0.25

60/60

7th story

25.5

4368

6256

0.3

80/80

6th story

22

5080

7278

0.35

80/80

5th story

18.5

5792

8301

0.40

80/80

4th story

15

6504

9323

0.44

80/80

3rd story

11.5

7216

10346

0.49

80/80

2nd story

8

7928

11368

0.54

100/100

1st story

4.5

8640

12390

0.69

100/100

Bas. 1

0

9512

13675

0.65

100/100

Bas. 2

-3.5

10384

14960

0.71

100/100

  • In TBDY 2018 7.3.1, the condition that the cross section dimension of the columns with high ductility level with rectangular cross section can not be less than 300 mm is also provided.