Chapter 11, Problem 11.3.19P

The roof over a concourse at an airport is supported by the use of pretensioned cables. At a typical joint in the roof structure, a strut AB is compressed by the action of tensile forces Fin a cable that makes an angle $\alpha$= 75° with the strut (see figure and photo). The strut is a circular tube of steel (E = 30,000 ksi) with outer diameter d₂= 2.5 in. and inner diameter d₁= 2.0 in. The strut is 5.75 ft long and is assumed to be pin-connected at both ends.

Using a factor of safety n = 2.5 with respect to the critical load, determine the allowable force F in the cable.