The figure shows the free body diagram of the beam. The reaction forces at C are C subscript x and C subscript y directed horizontally to the right and vertically upwards respectively. The load on the beam is 3.6 meters times w kilo newton per meter and it acts at a distance of 1.8 meters from C. The force along the support rod directed away from the point B is F subscript 1 at an angle of 35 degrees with the horizontal.

Consider axial member (1). The limiting stress in this member is specified as 50 MPa, and a factor of safety of 2.0 is required. The allowable normal stress for member (1) is therefore:

σallow=50 MPa2.0=25 MPa

Based on this stress, the allowable force magnitude for member (1) is:

F1,allow=σallowA1         =(25 MPa)(3,080 mm2)         =77,000 N=77.0 kN

In the preceding scene, it was shown that the force in member (1) could be expressed in terms of w as:

F1=(-2.2595 m)(w kN/m)

Equate these two expressions and solve for w.
Since only the magnitude of w is desired, consider the absolute value of F1.

(-2.2595 m)(w kN/m)=77.0 kNw=34.08 kN/m