Spireix
Spireix
IS 456:2000 CLAUSE 39.3 & 25.4

IS 456 Column Axial Load & Rebar Checker

Verify short axially loaded rectangular RCC columns against limit state of collapse, slenderness limits, minimum eccentricity (emin), and lateral tie spacing.

1. Column Dimensions & Height

2. Material Grades & Applied Load

Working load × 1.5 load factor per IS 456 Table 18.

3. Longitudinal Rebar Selection

Provided Area of Steel (Asc):1885 mm²

Axial Load Capacity (Pu,calc)

Checking...
-- kN
Factored load capacity per Cl. 39.3: Pu = 0.4 fck Ac + 0.67 fy Asc
Steel Percentage (pt):--%
Slenderness Ratio (Lex/D, Ley/b):--
Min. Eccentricity Check:--
Lateral Ties (Pitch & Dia):--

Cross-Section & Detailing

Cover: 40mm

IS 456:2000 Column Design Principles & Formulas

1. Axial Capacity (Cl. 39.3)

When minimum eccentricity does not exceed $0.05 D$, the axial strength of a short column with lateral ties is governed by:

Pu = 0.40 fck Ac + 0.67 fy Asc

Ac = Ag - Asc. For spiral columns, this capacity is multiplied by 1.05 per Clause 39.4.

2. Minimum Eccentricity (Cl. 25.4)

All columns must be designed for an unavoidable minimum eccentricity of:

emin = (L / 500) + (D / 30) >= 20 mm

If emin > 0.05 D, the column must be designed for combined axial compression and bending (uniaxial/biaxial moment).

3. Lateral Ties (Cl. 26.5.3.2)

Ties prevent outward buckling of main vertical bars.

• Diameter: ≥ max(φmain / 4, 6 mm).

• Pitch (Spacing): ≤ min(b, 16 φmain, 300 mm).

Frequently Asked Questions (IS 456 Column Design)

What is the minimum and maximum steel percentage allowed in RCC columns?

Per IS 456:2000 Clause 26.5.3.1, the minimum reinforcement is 0.8% of the gross sectional area (Ag) to resist buckling and shrinkage. The maximum steel is 6.0% for non-lap zones and 4.0% where bars are lapped to prevent honeycombing.

What distinguishes a short column from a slender (long) column?

A column is categorized as a short column if both its effective slenderness ratios (lex/D and ley/b) are less than 12. If either ratio is 12 or greater, it is a slender column and secondary moments (P-Delta) must be accounted for using additional moments (Max, May).