Design of Threaded Fasteners

Class Activity $(20)$

The upside$-$down steel A frame shown in the figure is to be bolted to steel beams on the ceiling of a machine room using ISO grade $8\mathrm{.}8$ bolts. This frame is to support the $40-kN$ radial load as illustrated. The total bolt grip is $48$ mm $,$ which includes the thickness of the steel beam, the A$-$frame feet, and the steel washers used.

The bolts are size M$20$ x $2\mathrm{.}5.$

a$)$ What tightening torque should be used if the connection is permanent and the fasteners are lubricated?

b$)$ What portion of the external load is taken by the bolts? By the members?

Solution: