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Mid-America Transportation Center

Reliability-Based Bridge Evaluation Criteria for Railway Bridges

Final Report
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Researchers

  • Principal Investigator: Andrzej Nowak (anowak2@unlnotes.unl.edu 402-472-1376)
  • Project Status
    Complete
    Sponsors & Partners
  • University of Nebraska-Lincoln
  • About this Project
    Brief Project Description & Background
    Railway bridges are subject to aging and require rational criteria for evaluation. The study will develop reliability-based evaluation procedures that will be used as a basis for rational load and resistance factors. Acceptance criteria will be closeness to the target reliability index.
    Research Objective
    The objective the proposed study is to develop statistical models for loads and resistance, select the target reliability levels for railway bridges, and determine rational evaluation criteria for bridge owners. The major contribution of the project is the developed load models that are representative for the actual and expected freight trains. The load model is to be used as a practical tool for evaluation of existing railway bridges.
    Potential Benefits
    The project results will include: statistical models for railway loads, evaluation procedures, reliability analysis procedures, acceptability criteria (target reliability indices) for railway bridges, procedures for determination of the remaining life time of bridges.
    Abstract
    Performance of bridges strongly influence operation of railway transportation network. Railway bridges constitute a vital part of the transportation infrastructure system and they are vulnerable to extreme events such as natural disasters and hazards stemming from negligence and improper maintenance, collisions, scour, intentional acts of vandalism, and terrorist attacks. Moreover, railway bridges are subjected to dynamic loads causing resonance phenomena in the structure. The simplified methods for evaluation of dynamic impact factors available in engineering code provisions do not cover possibility of resonance. In case of resonance excessive bridge deck vibration can cause loss of wheel/rail contact, destabilization of the ballast, exceeding the stress limits and in consequences reduction of the safety margin. Railway bridges are very important and must be protected by assessment of the appropriate level of safety. Considerable new developments took place for highway bridges, in particular, reliability-based design and evaluation codes. The available methodology can be now applied to railway bridges. The current approach to risk is often not rational. In addition, over 70 percent of railway bridges were constructed before 1950, and they require special attention. The objective the proposed study is to develop statistical models for loads and resistance, select the target reliability levels for railway bridges, and determine rational evaluation criteria for bridge owners. The major contribution of the project is the developed load models that are representative for the actual and expected freight trains. The load model is to be used as a practical tool for evaluation of existing bridges. The load rating model and procedures for determination of remaining life time of bridges will find important applications in decision making process regarding operation, maintenance, repair, rehabilitation and replacement. They will allow owners for prioritization of structures for repair/rehabilitation or replacement.
    Project Amount
    $ 95,369.81