Diaphragm braced strut-purlins are commonly used in the roof systems of metal buildings. However, the design problem of combined uplift and axial loads on these members is not adequately addressed in the 1989 AISI specification. The objective of this thesis is to provide experimental evidence that strut-purlins can be designed with an existing interaction equation. It was a/so the objective of this thesis to find a method of determining the axial capacity of diaphragm braced strut-purlins and to experimentally verify the accuracy of the method.