A three hinged arch shown in Figure is quarter of a circle. If the vertical and horizontal components of reaction at $$A$$ are equal, the value of $$\theta $$ is

The strain energy stored in member $$'AB'$$ of the pin jointed truss shown aside when $$'E'$$ and $$'A'$$ are same for all members is

The plastic modulus of a section is $$4.8 \times {10^{ - 4}}\,\,{m^3}.$$ The shape factor is $$1.2$$. The plastic moment capacity of the section is $$120$$ $$kN$$-$$m.$$ The yield stress of the material is

The steel portal frame shown in figure is subjected to an imposed service load of $$15$$ $$kN$$. Compute the required plastic moment capacity of the members. All the members are of the same cross-section. Draw the collapse load.