ABSTRACT
Pre-scientific use of arches as structural mechanisms favored a reliance on the proportions and dimensions of successfully completed arches and eschewed experimentation. William Edwards chose load-bearing masonry arches as the structural system for the bridge because this had been a safe and predictable structural option for bridges and buildings. Form-resistant structures like arches use their form as the primary means of diverting and resisting loads. Masonry arches rely on the predictable behavior of certain materials under compression to transmit loads and to serve as the literal building blocks of the structure. Designing and constructing arches followed centuries of trial-and-error experience and used an easily replicated, oft-repeated process for form-finding and construction. Arches might be considered primarily planar or extruded forms, since their profiles are represented two-dimensionally, and arched bridges are linear. Confirmation for a three-hinged arch can instead be found with mathematics and/or graphic statics.
