Long-term structural health monitoring for long span bridges---Temperature and traffic effects.

Long-term structural health monitoring for long span bridges---Temperature and traffic effects

Monitoring of the I-39 Kishwaukee Bridge

This report details the continuous monitoring of the Kishwaukee Bridge. The data collected includes measurements such as bridge deck acceleration, temperature changes, and crack opening displacement data from local deformation gages. The monitored data also includes modal frequencies, shear strain at known crack locations, and daily truck traffic. The instrument response provides needed information for real-time inspection and planned maintenance and rehabilitation. The main objective of this research was to continue monitoring of the bridge through the retrofitting contract and beyond to validate that the design and retrofitting strategy performed on the bridge arrested the crack growth. The measurements collected from this study will be used to infer possible structural changes and to guide retrofit strategies for compromised components, ensuring the bridge’s integrity and stability into the future. 17.ICT-27-9published or submitted for publicationnot peer reviewe

Application of elasto-magnetic based stress sensors for measurements of cable tension force in cable-stayed bridge

Recently, a novel stress sensor, which utilizes the elasto-magnetic (EM) effect of ferromagnetic materials, has been developed to measure stress in steel cables and wires. In this study, the effectiveness of this EM based stress sensors for monitoring of the cable tension force of a real scale cable-stayed bridge is investigated. The reference forces were used to calibrate and validate cable tension force measurements from the EM sensors. Tension force variations of two test cables during the second tensioning work on Hwa- Myung Bridge were monitored using the EM sensors

Comparative Field Study of Cable Tension Measurement for a Cable-Stayed Bridge

Cable tension is one of the important indexes of cable integrity as well as bridge stability and can be measured by various tension measurement methods. In this study, three widely used methods (i.e., the lift-off test, electromagnetic sensor method, and vibration method) have been implemented for two multistrand cables of a cable-stayed bridge under construction. The test bridge is Hwamyung Bridge in Korea, which has a prestressed concrete box girder. The field tests are executed during the second tensioning stage just after the installation of the key segment. The tensions are estimated before and after tensioning the cable and 5 days later (i.e., after finishing the tensioning of all the cables). The tensions measured by the three methods are compared with the design tension of the tensioning stage, and all three methods show very good performance in accuracy with minimal difference. Their cost and difficulty are compared based on test experiences. Additionally, an improved vibration method is proposed by ignoring apparent negative bending stiffness identified from measurement errors and validated in this test by improving the accuracy.close0

Field application of elasto-magnetic stress sensors for monitoring of cable tension force in cable-stayed bridges

Recently, a novel stress sensor, which utilizes the elasto-magnetic (EM) effect of ferromagnetic materials, has been developed to measure stress in steel cables and wires. In this study, the effectiveness of this EM based stress sensors for monitoring of the cable tension force of a real scale cable-stayed bridge was investigated. Two EM stress sensors were installed on two selected multi-strand cables in Hwa-Myung Bridge, Busan, South Korea. Conventional lift-off test was conducted to obtain reference cable tension forces of two test cables. The reference forces were used to calibrate and validate cable tension force measurements from the EM sensors. Tension force variations of two test cables during the second tensioning work on Hwa-Myung Bridge were monitored using the EM sensors. Numerical simulations were conducted to compare and verify the monitoring results. Based on the results, the effectiveness of EM sensors for accurate field monitoring of the cable tension force of cable-stayed bridge is discussed.open0