A homogeneous, simply supported prismatic beam of width $$B,$$ depth $$D$$ and span $$L$$ is subjected to a concentrated load of magnitude $$P.$$ The load can be placed anywhere along the span of the beam. The maximum flexural stress developed in beam is

A three hinged parabolic arch $$ABC$$ has a span of $$20$$ $$m$$ and a central rise of $$4$$ $$m.$$ The arch has hinges at the ends and at the center. A train of two point loads of $$20$$ $$kN$$ and $$10$$ $$kN$$, $$5$$ $$m$$ apart, crosses this arch from left to right, with $$20$$ $$kN$$ load leading. The maximum thrust induced at the supports is

The unit load method used in Structural analysis is

For a linear elastic structural system, minimization of potential energy yields