Performance evaluation of spanning systems

Abstract

The design of spanning systems is a common task that structural engineers perform, and beam theory is one of the first things taught in a mechanics course. This thesis studies a range of spanning systems, and evaluates their performance in a systematic way. The systems considered are beams, trusses, funicular structures, and cable-stayed systems. The first part of the thesis examines system selection by evaluating the limits to each structural system and the relative efficiency of structural systems at different spans, depths, and loading constraints. In the second part, dynamic performance and global buckling are investigated to determine their influence on the performance of beams and trusses. These failure mechanisms should be examined early in the design process, but similar types of studies rely only on static behavior to evaluate performance. The third part analyzes the effect of the length-to-depth ratio on the performance of beams and trusses. In conceptual design, rules of thumb for this ratio are used as a starting point, but may not always be appropriate depending on the situation. Finally, the effect of design constraints on the performance of beams and trusses are studied. Depending on the situation, these design constraints may negatively affect the spanning system's performance. Specifically, the constraints of deflection, local buckling, uniform sizing of truss members, and support conditions are explored.