About the research
There is a nationwide need for a safe, efficient, and cost-effective transportation system. An essential component of this system is bridges. Local agencies perhaps have an even greater task than federal and state agencies in maintaining the low-volume road (LVR) bridge system due to lack of sufficient resources and funding.
The primary focus of this study was to review the various aspects of off-system bridge design, rehabilitation, and replacement. Specifically, a reference report was developed to address common problems in LVR bridges. The source of information included both Iowa and national agencies. This report is intended to be a “user manual” or “tool box” of information, procedures and choices for county engineers to employ in the management of their bridge inventory plus identify areas and problems that need to be researched
To obtain pertinent published information, past Iowa Highway Research Board (IHRB) projects were identified and reviewed. These reports were briefly summarized and cross-referenced to the various final reports. In addition, literature reviews were performed to identify pertinent information related to LVR bridge design, rehabilitation/strengthening and replacement. Relatively detailed summaries of rehabilitation/strengthening methods are presented. A questionnaire was sent to all Iowa county engineers to determine the various problems that are encountered on LVR and their solutions to these problems. Fifty-two Iowa counties responded to the survey. A large percentage of the respondents indicated that they use in-house crews for bridge replacement or rehabilitation. A large part of the in-house work uses steel stringers and wood decks. Approximately one-half of the respondents indicated that they have experience with strengthening superstructure and substructure bridge elements, although adding piling to the substructure was the most common response. A questionnaire was also sent to other states to obtain similar information. The questionnaire was sent to State DOTs, County and Local bridge owners, and consultants involved with off-system bridge design and rehabilitation. The assistance of the National Association of County Engineers (NACE) was employed to disseminate the survey to all potentially interested parties. In all, several hundred surveys were distributed electronically via email. The response to the questionnaire included a total of 20 states and 70 local agencies nationally.
One significant finding is that more appropriate decisions are required in all areas of bridge maintenance, rehabilitation, and replacement. “Data-based” decisions through asset/bridge management as well as construction techniques, maintenance procedures, materials, etc. to promote extended life are required. New high-performance materials as well as fiber-reinforced polymer (FRP) products are currently being researched. Several of these materials show promise for use in off-system bridges since they have excellent durability, require minimal maintenance, and appear to have long life. A list of research needs was developed, based on the evaluation of the information obtained from this study (i.e., comparing current state-of-the-art with existing problems), input from a research needs forum meeting held last year, and conversations with several county engineers. The research needs list will form the basis of a work plan for developing solutions to current LVR bridge problems.