OVERVIEW NO 92 - MATERIALS AND SHAPE

A procedure is described for selecting materials and section shapes for load-bearing components. The choice depends on the mode of loading (tension, bending, torsion), on the available shapes (solid sections, tubes, I-sections and so on), on the properties of the material of which the shape is made (modulus, strength, density), and on some criterion of performance (minimising weight, for instance). A distinction is drawn between macroscopic and microscopic shape, both of which can increase performance in bending or twisting, and which can be combined to give very efficient structures. The approach gives insight into the efficiency of natural materials such as wood; and it suggests routes for developing new, efficient, material-shape combinations.