Under wind and traffic loading, slender long-span bridges can experience large responses which are typically caused by the dynamic interaction of the loads with the bridge structure. These large responses can cause fatigue accumulation, deterioration, and, at times, related safety issues for the bridge system. In the United States, more than 800 long-span bridges contained in the national bridge inventory are classified as fracture-critical. This project will study these dynamic interactions and their potential to cause damage in long span bridge structures. The project will focus on understanding the dynamic behavior of bridge structures and develop an integrated dynamic model to assess the lifetime performance of long-span bridges under combined wind and traffic loads. A reliability-based analytical approach which utilizes improved traffic flow simulations combined with wind tunnel test data will be formulated to define equivalent wheel loads and the resulting factored design loads to ensure a targeted reliability level at several levels of expected performance.
This research will help engineers to reliably predict the response, performance, and remaining life of slender long-span bridge systems. It will help to identify potential sources and risk of damage to current bridges with the ultimate objective of designing retrofit measures to improve performance and prolong the lives of the long span bridge structures. The reliability-based analysis and design methodology will be helpful in load calibration and in achieving a consistent level of risk for all bridge structures, which is the fundamental intent of any design specification. Such a consistent level of risk is not necessarily guaranteed now due to the lack of design specifications for long-span bridges. The research results will be widely disseminated to other researchers and practitioners through conventional mechanisms and committee work. The project will provide advanced training to graduate students. Outreach educational activities are also planned to provide an opportunity to pre-college students to participate in cutting edge research with hands-on experience with wind tunnel experimentation, thus helping to foster interest in the next generation of engineers.
In the United States, more than 800 long-span bridges in the national bridge inventory are classified as fracture-critical. Although the total number of long-span bridges is relatively small compared to short-span and medium-span bridges, long-span bridges often serve as backbones for critical interstate transportation corridors as well as often serve as evacuation routes, underscoring the importance of their continued integrity in normal service conditions as well as in extreme emergency conditions. Two examples are the Sunshine Sky Bridge in Florida and the Luling Bridge in Louisiana. The lack of an accurate and systematic performance analysis for slender long-span bridges with in-depth evaluations based on combined loading such as traffic and environmental impacts has been found to be the primary reason for this deficiency. Therefore, there is a significant need to develop a general dynamic analysis methodology that is capable of estimating the dynamic performance of slender long-span bridges under combined extreme loads. This project dealt with an important infrastructure issue – introducing an integrated long-span bridge dynamic analytical model and the characterization of design loads and limit states for long-span bridges. The research results will lead to progress in the state-of-the-art in understanding slender long-span bridge performance in a more realistic and accurate way. As a result, future long-span bridges can be designed more safely and reliably. This research will also help people identify the remaining useful life and potential sources of degradation as well as the risk of damage to current bridges, thus helping prolong the lives of these bridges. The specific broader impacts include: Broader Impact 1: Providing an improved and integrated methodology for slender long-span bridge analysis which considers interacting complex loads; Broader Impact 2: With the application of reliability-based analysis to slender long-span bridges and load calibration, long-span bridges in the U.S. will have a consistent level of risk from bridge to bridge, which is the fundamental intent of any design specification. Broader Impact 3: The educational portion of the project resulted in introducing pre-college students to cutting edge research and research equipment (wind tunnel), thereby helping to foster interest for the next generation of engineers. Impact to Research Community The approach proposed herein combines many key areas of analysis, but more importantly begins the process of developing a general analytical platform for slender long-span bridges. Several key innovations within the proposed study will enhance the understanding of traffic flow simulation, bridge design, bridge safety as well as related basic engineering and science. The wind tunnel testing results will also be useful to the bridge aerodynamic and transportation research communities.
