About the research
The objective of the research was to determine the frequency and cause of resonant vibrations of vertical truss members on bridge A4497 over the Missouri River in Jefferson City, Missouri. Instrumentation to monitor the vibrations of four vertical members was installed on the bridge and monitored for 42 days. Weather data available from the weather station at the Jefferson City Memorial Airport were used to analyze weather conditions causing resonant vibrations of the four vertical members.
Eleven vibration “events” were found where vertical members vibrated with higher than normal acceleration. The researchers also analyzed historical weather data to determine how frequently the resonance vibrations were occurring. The research team concluded that the frequency of resonant vibration events was likely 0.25 or fewer events per day. The vibrations were caused by average winds from the west-northwest, northwest, or southwest of approximately 17 mph or greater, based on monitoring results.
Recommendations stemming from the research are as follows:
- The effect of the vibration events on the durability of the vertical truss members should be analyzed further to determine if a retrofit is necessary. The data provided through the field monitoring should be used in the analysis.
- Other vertical members of similar lengths should be monitored to determine if they are also affected by resonant vibrations.
Midwest Transportation Center
Missouri Department of Transportation ($15,000.00)
Contract Number: DTRT13-G-UTC37