Jun 18, 2021

Home STRUCTURAL DESIGN GUIDELINES FOR COLUMNS DESIGN | REQUIREMENTS FOR COLUMNS DESIGN | LCETED

GUIDELINES FOR COLUMNS DESIGN | REQUIREMENTS FOR COLUMNS DESIGN | LCETED

LCETED STRUCTURAL DESIGN,

GUIDELINES FOR COLUMNS DESIGN | REQUIREMENTS FOR COLUMNS DESIGN

Width of the column, B ≥ 300 𝑚𝑚 and 𝐵/𝐷 ≥ 0.4

Width of the beam, B ≥ 200 𝑚𝑚 and 𝐵/𝐷 ≥ 0.3

If the span of beam > 5 𝑚 (B ≥ 300 𝑚𝑚 and 𝐵/𝐷 ≥ 0.3)

Better to apply clear cover of 40 mm to ties NOT to main bars.

Common bar sizes = 16, 20 and 25 mm.

For preliminary sizing of columns, use 1% of 𝐴_𝑔. (generally, 1.5-2% in GF, and 1-1.5% in roof)

Practically, max. area of steel = 3% to avoid congestion at splicing section.

C/C spacing of main bars ≯ 300 mm. In any case, parallel leg spacing of a tie < 300 𝑚𝑚.

No. of bars in 230, 300, 450, 600, 750 sides are 2, 3, 4, 6, 7 #

For proper detailing of the column as well as EQ requirement, min. size of column = 300 mm.

For beams, min. requirement of width is 230 mm so that at joints beam bars easily pass through column reinforcement.

Min. 4 bars in columns

if the size is 400 x 400 as in that case spacing between bars is less than 300 mm 400 − 40 × 2 − 8 × 2 − 12 = 292 𝑚𝑚 .

It is advisable to provide additional ties at splicing location of longitudinal bars.

If tie bar is bent through 135˚, then bent length is 8𝜙

For EQ design, pitch of tie = 1/2 × 𝐿. 𝐿.𝐷.

Maximum distance B/W end restraint ≯ 60 × 𝐿. 𝐿.𝐷 (Columns for aesthetic purposes near the entrance of buildings).

For EQ design, lap splices should be only in the central portion of columns beams (away from plastic hinge locations). Spacing of ties in splice portion = 150 mm.

For EQ design, lesser spacing of ties near beam/column joint (150 mm)and more spacing towards centre.

For EQ design, min. number of bars in rectangular column = 8, for gravity load = 4

For EQ design, 𝜙 𝑡𝑖𝑒 = 8𝑚𝑚. If 𝜙 𝑙𝑜𝑛𝑔 > 25 𝑚𝑚,𝜙 𝑡𝑖𝑒 = 10𝑚𝑚

For EQ zones, spacing of longitudinal bars =200 mm or 1/3 the dimension in the considered direction for (rectangular column) or 1/3 the diameter (circular col.)

It is advantageous to use higher conc. Grade in column (M 25). Results in less size and steel.

L-, T, or + shaped columns are often used at outside and re-entrant building corners for architectural purposes, but they should not be used in EQ zones as they may crack at re-entrant corners.

Better to provide equal reinforcement on all sides whether the column is uni-axial or bi-axial

Above the top of the footing, a pedestal of height 250 mm is provided with 1#12 𝑚𝑚 𝜙 𝑈 −shaped bars are provided at each face of the pedestal.

In the design of column, assume 𝐿𝑒𝑓𝑓 = 𝐿 (this is on safer side)