ABSTRACT
The primary reason for the existence of structures is, of course, the practical purpose that they serve. Structures support loads from their location of application down to the ground, although typically not by means of the shortest possible
"route" between those points since open and structure-free spaces of various sizes and shapes are needed in orderto inhabit a building. This isthe natural order of the relationship between the "why" and the "how," of reason and consequence: practical purpose comes first, and physical necessity follows. The practical purpose that the structure is assigned, its utility aspect, is fairly straightforward to accept and appreciate: in the case of bridges, for example, this is made clear by acknowledging the fact that the principal utility function, its "raison d'etre" so to speak, is typically that of transporting people and goods across a valley, a river, or a stretch of sea; i.e., it is all about establishing a transport line from one bank to the other. The straight line of communication that this link commonly results in will most likely suggest a certain structural configuration, either as a construct that becomes an integral part of the structural system, or else as setting up the conditions for how this line should be supported. The utility function provides in either case highly important input for how a structure is actually designed as well as an understanding of the form of bridge that is possible.
