04/11/2025
Axial Load Calculation in Building Design
1.Step-by-Step Procedure
1. Identify loads (Dead, Live, Other vertical loads).
2. Find tributary area (A).
3. Compute floor/roof loads: PD
= D × A, PL
= L × A.
4. Add column self-weight and point loads.
5. Apply load combinations (1.2D + 1.6L etc).
6. Check axial capacity and buckling.
7. Revise section if capacity < demand.
2.Useful Formulas
Tributary Load: P = (D + L) × A
Euler Buckling: Pcr = π²EI / (KL)²RC
Axial Strength: Pn= 0.85f'c(Ag- As) + fyAs
Steel Pn= Agfy
3. Example Calculation
Data:
Dead load = 5.0 kN/m²
Live load = 3.0 kN/m²
Tributary area = 16 m²
No. of floors = 3
Column self-weight = 20 kN
Load combo = 1.2D + 1.6L
Per floor D = 5×16 = 80 kN
Per floor L = 3×16 = 48 kN
Total D = 80×3 + 20 = 260 kN
Total L = 48×3 = 144 kN
Factored load = 1.2×260 + 1.6×144 = 542.4 kN
■ Axial Load on Column = 542.4 kN
4. Design Checks
✔ Compare Pu
≤ φP
n
✔ Check slenderness (KL/r)
✔ Check combined axial + bending (interaction diagram)
✔ Apply all load combinations
✔ Include second-order (P–∆) effects
5. Quick Checklist
■ Correct tributary area
■ Include finishes & partition loads
■ Include point/concentrated loads
Related Hashtag:
