Historic American Engineering Record Grant for Howe Truss Performance Engineering Studies

Heritage Documentation Programs, specifically, the Historic American Engineering Record, is engaged in a multi-year study funded by the Federal Highways Administration documenting historic covered bridges. The work proposed to be performed under this agreement will be engineering studies of historic truss performance, a critical but difficult to perform type of documentation.

A classic Howe truss with cast-iron nodes will be selected and a series of engineering studies carried out, culminating in a report on the behavior of the Howe truss under load. Because of the difficulties of performing these studies in the field with an in-use structure, they will be undertaken in an engineering laboratory once the truss has been disassembled, moved, and reassembled. The truss will be shored, verticals loosened, instrumentation installed, nuts tightened to change stress levels in members, shoring removed, and live loads applied. The resulting data will be useful in calibrating analytical models for the Howe truss. The final report will complement documentation (measured drawings, historical report and large-format photographs) produced by HAER, and will provide understandable, practical information on the behavior, modeling, and design of Howe truss bridges. The results will have application to many of the 140 Howe trusses in existence, and it could also be used in designing new covered bridges.