Evaluation and Rehabilitation of Historic Metal Truss Bridges: A Case Study of an Off-System Historic Metal Truss Bridge in Shackelford County, Texas. (Revised)

摘要

This report documents the results of a case study of an off-system historic metal truss bridge in Texas. Off-system bridges are not on the state highway system and are typically located on country roads or city streets. There are a large number of older off-system metal truss bridges still in vehicular service in Texas, many of which are of significant historical interest due to their age and other unique features. The primary objective of the study reported herein was to address structural issues involved with historic off-system metal truss bridges. More specifically, the objective was to examine methods that can be used to develop an accurate and realistic load rating for an old metal truss bridge, and methods that can be used to strengthen a bridge if needed. The case study bridge is located in Shackelford County, Texas on County Road 188 near Fort Griffin, crosses the North Fork of the Brazos River and was originally constructed in 1885. The study of the Shackelford County Bridge was divided into five major tasks: (1) collection of data on the bridge; (2) evaluation of materials; (3) structural analysis and load rating; (4) field load testing; and (5) development of rehabilitation options. Each of these tasks is described in detail in this report.