ABSTRACT
Long span bridges are the key structures for transportation system of countries. In addition to their construction costs, maintenance, management and safety of this type of large scale structures also become significant considerations to reliably continue their operational performance without any traffic flow interruption under extreme events, such as, wind, heavy truck, marathon, earthquake etc. Structural Health Monitoring (SHMs) system provides considerable information for tracking the current condition of long span bridges subjected to extreme events.
The existing suspension bridges in Turkey, the Bosphorus and the Fatih Sultan Mehmet bridges and the ongoing bridge projects, the Yavuz Sultan Selim bridge (the 3rd Bosphorus bridge) and the Izmit Bay bridge, are the main transportation connections between Europe, Asian and Africa. Due to continuously increase in population of Marmara region, the importance of these bridges raises increasingly. Especially, Istanbul city of intersections has crucial role in this region with the population of 18 million.
Since the Bosphorus Bridge experienced a critical event leading to damage to hanger element, a SHM system was required to be installed on the bridge for tracking its structural behavior. The Bosphorus Bridge with the main span length of 1074 m and two side spans supported at the base instead of hanger elements was instrumented in 2009. Totally 168 sensors including accelerometer, tiltmeter, strain gauge, force transducer, laser displacement, GPS, thermocouple, and weather station were mounted on the bridge. The SHM system has helped the authority responsible for the bridge’s safety and management to take necessary measures for extreme and daily events. Similarly, the Fatih Sultan Mehmet Bridge has also a SHM system of which capacity and function are limited compared to those of the Bosphorus Birdge. However, the SHM system consisting of triple direction accelerometers at the deck, approach and towers has ability to continuously collect data from the bridge. For the ongoing bridge projects, the Yavuz Sultan Selim and the Izmit Bay Bridges, preliminarily designed SHM system has been proposed considering the previous experiences for the existing bridges. The main advantage of newly established SHM system for these bridges is to be designed and installed during construction not after construction.
In this study, general properties of the bridges are given on the basis of Structural Health Monitoring considerations. The specifications of the SHM systems of both the existing and the bridges under construction are given in detail. Besides, the recent developments in these SHM systems are presented. Based on the growing interest in long span bridge projects in Turkey, the need for a general large center for the SHM systems of the all long span bridges in Turkey is stated in this study. This large SHM center also provides opportunity to implement the Structural Identification concept St-Id to the bridges in Turkey.
