A reinforced concrete structure has to be constructed along a sea coast. The minimum grade of concrete to be used as per IS: 456-2000 is

Rivets and bolts subjected to both shear stress $$\left( {{\tau _{vf}},\,cal} \right)$$ and axial tensile stress $$\left( {{\sigma _{tf,cal}}} \right)$$ shall be so proportioned that the stresses do not exceed the respective allowable stresses $${\tau _{vf,}}$$ and $${{\sigma _{tf,}}}$$ and the value of $$\left( {{{{\tau _{vf.cal}}} \over {{\tau _{vf}}}} + {{{\sigma _{tf,cal}}} \over {{\sigma _{tf}}}}} \right)$$ does not exceed

Beam $$GHI$$ is supported by these pontoons as shown in the figure below. The horizontal cross sectional area of each pontoon is $$8\,\,{m^2},$$ the flexural rigidity of the beam is $$10000$$ $$kN$$-$${m^2}$$ and the unit weight of water is $$10$$ $$kN$$/$${m^3}$$.

When the middle pontoon is removed, the deflection at $$H$$ will be

Cross-section of a column consisting of two steel strips, each of thickness $$t$$ and width $$b$$ is shown in the figure below. The critical loads of the column with perfect bond and without bond between the strips are $$P$$ and $${P_0}$$ respectively. The ratio $$P/{P_0}$$ is