QUESTION $1(10$ marks$)$

A load of $50kN$ is attached to a rigid beam BDF as shown in Figure $1.$ The beam is

attached to bars $AB,CD$ and $EF$ which are $2m$ long. Bars $AB$ and $EF$ are made of Steel

$)$ and $CD$ is made of Aluminium $(E_{Al}=73k\frac{N}{m}{m}^2).$ Calculate:

a$)$ the stress in the steel and in the aluminium bars

b$)$ the elongation of the bars after the load is attached to the beam