For a long time, there has been interest in how William Howe built his original Howe Trusses, which had iron verticals. An interesting aspect is that his original design permitted tightening of the metal verticals by turning the nuts to induce compression in the diagonals and tension in the chords. Colonel Long earlier used wedges in the joints of his patented trusses to modify the stresses in the diagonals, verticals, and chords. This research would study the design and performance of Howe truss bridges. A classic Howe truss in relatively decent condition could be selected and then shored, the verticals loosened, instrumentation installed, and the nuts tightened to change the stress levels in the members, the shoring removed, and live loads applied. Data could be gathered throughout this process and a time history of member forces and displacements will be analyzed and documented. The data would be useful in calibrating viscoelastic models for the Howe truss. The final report would provide understandable, practical information on behavior, modeling, and design for Howe truss bridges. The results could have application to many of the 140 Howe trusses in existence, and could also be used in designing new covered bridges.
The primary object of this project is to study in a historical context the design of, and determine the performance of, Howe truss bridges.