In an inevitably occurring process, bridges possessing historic, artistic, and engineering significance deteriorate and must be maintained and rehabilitated in order to be kept in service. Ideally, all potentially significant bridges would be properly preserved and continue to beautify and bring character to their surroundings for years to come. However, funding is currently limited for transportation projects in general, and even more so for historic bridge preservation, which some may consider less critical in comparison to other transportation needs. Because of this limitation on resources, it is important that bridge-owning agencies use proper planning and management strategies in order to make the best use of available funding. This thesis presents a framework designed to assist agencies in this process. The framework is devised specifically for TxDOT for use in Tarrant County, Texas, but can be used as a model for agencies anywhere with some modifications to fit the inventory under evaluation. Included in the framework are a methodology for prioritization of bridges within an inventory, guidance on financial and legal procedures, identification of potential funding sources, summary and review of condition assessment practices and bridge mitigation strategies, a template for individual bridge preservation plans, and a framework for resource allocation within a bridge inventory. It can be concluded from this research that early detection of defects, preventive maintenance, condition assessment beyond routine inspection, adjustment of evaluation methodology, and use of engineering judgment when using numerical evaluation methods are critical components of proper management of historic bridges.

Civil infrastructure throughout the world serves as main arteries for commerce and transportation, commonly forming the backbone of many societies. Bridges have been and remain a crucial part of the success of these civil networks. However, the crucial elements have been built over centuries and have been subject to generations of use. Many current bridges have outlived their intended service life or have been retrofitted to carry additional loads over their original design. A large number of these historic bridges are still in everyday use and their condition needs to be monitored for public safety. Transportation infrastructure authorities have implemented various inspection and management programs throughout the world, mainly visual inspections. However, careful visual inspections can provide valuable information but it has limitations in that it provides no actual stress-strain information to determine structural soundness. Structural Health Monitoring (SHM) has been a growing area of research as officials need to asses and triage the aging infrastructure with methods that provide measurable response information to determine the health of the structure. A rapid improvement in technology has allowed researchers to start using new sensors and algorithms to understand the structural parameters of tested structures due to known and unknown loading scenarios. One of the most promising methods involves the use of wireless sensor nodes to measure structural responses to loads in real time. The structural responses can be processed to help understand the modal parameters, determine the health of the structure, and potentially identify damage. For example, modal parameters of structures are typically used when designing the lateral system of a structure. A better understanding of these parameters can lead to better and more efficient designs. Usually engineers rely on a finite element analysis to identify these parameters. By observing the actual parameters displayed during field testing, the theoretical FE models can be validated for accuracy. This paper will present the field testing of a historic wrought iron truss bridge, in a case study, to establish a repeatable procedure to be used as reference for the testing of other similar structures.

This study investigates the complex issues surrounding the preservation of historic, single-lane, metal truss bridges. Essentially functionally obsolete, these structures are targeted for replacement due to current government transportation policies, funding requirements, and safety concerns. After these issues are discussed, a series of case studies from Hunterdon County, New Jersey, will highlight multiple bridge rehabilitation projects in which designs and plans were modified to suit the unique situations and conditions of each of these structures, without compromising historic integrity and improving safety. These bridges have important cultural value, and although in some cases the original structure may be lost or wholly reconstructed, the historic character of the bridge and area is retained. This thesis illuminates the difficulties that need to be overcome in attempting to successfully preserve historic, single-lane bridges and their rural context (while maintaining transportation functionality), and illustrates the important role of community involvement in the preservation process. / Department of Architecture