Gable Frame Design Considerations

Abstract

A gable frame design is reviewed with regard to the modeling, load specification, and strength evaluation. It is found that the approximation used for the boundary conditions at the column bases should adequately account for the behavior of the foundation and more than one approximation may be necessary. Uneven loading is shown to be very significant, and it is recommended that gable frames always be designed for some uneven distribution of load. The question of the correct effective length for the rafter is examined, and a nonlinear analysis or an approximate, but conservative, approach is suggested for gables with significant axial load in the rafter. One method of utilizing a frame buckling analysis in a conventional AISC evaluation is presented. It is suggested that if there is significant axial stress in the rafter, caution should be exercised in the use of specification limitations, which are based on girder behavior where there may have been no axial stress considered in the derivation and testing of the specification limitations.