PEDESTAL DESIGN AND REINFORCEMENT

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For small load carrying columns, the pedestals are designed without any reinforcement and with height less than three times its width. Generally hollow concrete blocks are used and the hollow place is filled with concrete. But this is only limited to small load ranges.


But in the case of large load columns, construction and design of pedestals is same as reinforced columns for major loads. Reinforcement is also provided for the pedestals but the amount of reinforcement is 0.15% of its cross sectional area.



 Minimum reinforcement shall be 0.15% of crossection area
(Refer clause 26.5.3.1 of IS 456 on pedestal having length less
than 3*least lateral dimension)
Minimum Bar dia - - Better use 12mm dia as minimum
Maximum spacing - - 200mm
(This is generally for mass concrete and the case of pedestal
seems closer to it)

Lateral ties - - Al around may be 10mm dia @200mm c/c maximum ,
But internal ties need to be provided ,may be ,at double spacing to connect
opposite face bars alternately .

But must check minimum reinf provided for:
(i) Tensile force due to wind uplift in case of sheds on trusses plus
any moment from column due to partial cladding
(ii) Tensile force due to wind uplift plus moment (at pedestal base) due to horizontal
reaction from hinged base frame in case of sheds with rigid steel
frames - - under wind conditions
(iii) Tensile force due to wind uplift plus
moment (at pedestal base) due to horizontal reaction from Fixed base
frame in case of sheds with rigid steel frames - - under wind conditions

alternately reinforcement on each face worked out considering as beam 
Ast(on each face) = M/tjd ,since direct stress is small.

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