975. Optimum Design of Semi-Trailers

Paper

Abstract

The major components of weight in a semi-trailer are the longitudinal beams, which are generally of I-beam section and designed from fatigue arid static failure criteria. The optimum design of these beams is considered with specific investigations into unsymmetrical I-beam sections, profiled beams and perforated webs. Each design has the same fatigue and static collapse strength and it is shown that up to 32% weight may be saved in these components, for a specific semi-trailer. Practical constraints on minimum thickness, maximum depth and constant flange area are accounted for.
A further aspect of the design of the chassis is the torsional loading, which may be resisted by transverse members. Four design cases are identified in this mode, and the influence of the member cross-section and disposition along the chassis is examined from the point of view of stress level in the members. In the absence of experimental data on torsional loading, realistic figures were assumed and the results indicated that several members are desirable. The optimum cross-section and disposition of these transverse members is discussed.