Shear web area and stiffness for cylindrical concrete section e.g. circular water tank

[omkar121]

Hi,

I am modelling a cicular concrete tank (20m dia, 0.8m wall thickness) using LMBM for seismic analysis. I seek guidance on the shear stiffness and shear web area to be considered. I have the shear modulus 'Gc' of concrete and the shear rigidity as per ASCE 43-05 is Gc x Aw. 'Aw' is the shear web area which for the rectangular section would be the gross cross-section area. However, what value should be considered for a hollow circular section ?

For hollow steel sections the shear area is approximatelt 60% to 67% of the gross cross-section area - is there a similar reduction applicable to concrete elements ?

I would appreceate your guidance.

Thanks.