Column Pre-Dimensioning

Symbols

A_c = Reinforced concrete column cross-section area
f_cd = Concrete design compressive strength
N_d = 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 N_d ≤ 0.9f_cdA_c .

• 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.

Open

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

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Selected Column Front Dimensions

• 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.