RC Details of Columns

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 Columns

SCOPE:

 Rectangular Column 
 Circular Column 
 Irregular shaped Column

DETAILING STANDARDS: 

Nominal Cover to Reinforcement:

Internal : 30mm + Δcdev (5 or 10mm) 
External : 35mm + Δcdev (5 or 10mm) 
Max. cover to avoid concrete spalling : 40mm to link or 70mm to axis of main bars or surface mesh to be provided  

Spacing, Number and Size of Main bars:

Minimum spacing : 75mm (at laps) 
Maximum spacing : 300mm 
Minimum number : 4 nos (6 nos for Circular Column size >200mm) 
Minimum bar size : 16mm (>8mm for column thickness < 200mm) 

Spacing and Size of Links:

Minimum spacing : 25mm (Clear spacing) 

Maximum spacing : ≤ (20E or 12B x main bar Ø) or (Least size of column) E or 400mmE
 
Maximum spacing at laps and soffit of slab or beam : ≤ (12 x main bar Ø) or (0.6 x Least size of column) E or 240mmE or (200mm at laps, if both lapping bar Ø > 20mm and the cover < 1.5Ø) B
 
Maximum lateral spacing of legs : Main bar from a vertical leg ≤ 150mm 

Minimum bar size : 8mm

Bar arrangements:

Typical Column details:




Typical Links arrangements:




Crank Length Calculation: 




* - No crank is required for bars ≤ 12mm. 
# - Mechanical splices using couplers to be considered in confirmation with client for bars ≥ 32mm to avoid congestion.


Column Offset details: (Transition detail)


Reinforcement arrangement at column offset location to be detailed as shown in Detail-A and additional links may be required to locate the starters above as shown in Detail-C. 


Reinforcement can be cranked and continued above as shown in Detail B, if column offset (X) is less than the limited value of 100mm (the limited value to be reduced to 50mm where the same bar cranked at bottom). Detail-B to be replaced with Detail-A when crank height (Z) is more than the slab or beam depth (Y).




Where,
Superscript as B means British code
Superscript as E means EC2

T L is Tension lap
T A is Tension Anchorage
C L is Comparation lap




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