Sustainable Bridges: The Thread of Society 1 AP: NN/NNNN © ABC 2011 The history and service of timber Howe truss bridges in Australia By Ian Berger BA (Hons) 1 Roads and Traffic Authority of NSW Synopsis The Howe truss was patented in USA initially in 1840 and again in 1842 and went on to become one of the primary timber truss designs used in North America. The adaptation of the Howe truss in NSW into the two distinct forms known as the “Allan” and “Dare” trusses is well documented, though its usage elsewhere in Australia is largely ignored. This paper will briefly describe the extent of this usage and suggest the manner in which some of the bridge engineering knowledge required for their construction was transmitted. The Howe truss in North America The adoption and development for bridges blossomed in the USA during the 19 th century. So many bridges were required in America that bridge building became a profitable industry for bridge designers. There were many types of bridges patented of which the Howe was prominent. William Howe of Massachusetts was granted his first truss patent in 1840 and extended the patent with improvements in 1850. His 1850 patent used metal rods as the vertical members of what was otherwise a simple timber parallel-chord, cross-braced truss. This was the first truss patent granted with some major structural components made with metal. The configuration used easy-to-erect and readily prefabricated components that could be assembled on site and adjusted via threaded connections at the rod ends (US DOT, 2005). Little skilled labor was involved in assembling and erecting this truss type, and it became an immediate success (see figure 1). Figure 1. Diagram of Howe truss based on patent issued in 1850 (US DOT, 2005).