Traditional structural analyses of truss bridges are based on a “skeleton” frame analysis, the classic textbook method, which has been used since 1847 (Rutz 2004b). While the techniques of analysis have changed – computer analysis vs. manual calculations – the basis has remained basically unchanged. Engineers are so accustomed to this direct methodology that alternative load paths are customarily neglected. Further, seldom does the practicing engineer have the budget to complete time-consuming analytical studies, nor the inclination to accept liability for new and untried methodologies.
raditional structural analysis is based on a “skeleton” frame, such as is illustrated in Figure 2.1. The “computer” in the 19th century design office was the individual who completed the calculations, using the classic textbook methods of joints and sections (Ketchum 1908) or graphical methods that simplified some of the arithmetic (Waddell 1898a). Today’s practitioner using one of the many readily available computer programs is really utilizing matrix algebra. The “computer” is now a machine, but it does the same job – it performs the calculations. While the practices have changed, the fundamental basis is still the same – a “skeleton” frame is still assumed.
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