The kern area (core) of a solid circular section column of diameter, $$D$$ is a concentric circle of diameter, $$'d'$$ is equal to

The axial load carrying capacity of a long column of given material. Cross-sectional area, $$A$$ and length, $$L$$ is governed by

The plane structure shown below is

A plane frame $$ABCDEFGH$$ shown in figure below has clamp supports at A and axial force release (horizontal sleeve) at $$'C'$$ and moment release (hinge) at $$E.$$ The static indeterminacy of the frame is