Analysis, Design & Performance
Full Session with Abstracts
335009-1 - Efficient design of trusses guided by design diagrams
Saturday, April 21
10:00 AM - 11:30 AM
Paper and presentation will discuss how to generate and use diagrams for efficient design of trusses. Engineers often are forced to use intuition or rules of thumb to come up with an efficient truss type or truss proportions for a given load/span condition. It appears that simple design aiding diagrams can be created and used in general situations. These charts can be easily used to estimate structural quantities before the truss is even designed. Also, if: load, span, deflection criteria are known an optimal depth and type of truss can be quickly obtained. Strength and stiffness criteria are considered in generation of these diagrams. These diagrams can also be used to estimate a penalty on structural quantities when a design is forced away from optimal.
Multiple sample diagrams are going to be provided in the paper together with the theoretical derivations. Optimization process based on virtual work method will be discussed. Size of some structural members are often governed by strength and not stiffness. Procedure of constraining selected truss members to a given section sizes will also be discussed.
Design aiding diagrams are generated based on large number of designs. These results before they can be used in a general situation need to be brought to a unit-less state. This operation is obtained via scaling of multiple parameters that influence the designs. Procedure how fully unit-less charts are obtained will be explained.
Finally, several examples will be presented. It will be shown how optimum topology of a truss can change for various loading or deflection criteria. It is not commonly known that optimum layout of a spanning truss is influenced by stiffness and strength of the structural material utilized.
The goal of the presentation is to explain how certain properties influence simple span truss design and to teach how to design a truss most efficiently using truss design charts.