Progressive collapse assessment of Osmangazi Suspension Bridge due to sudden hanger breakage under different loading conditions

The design life of suspension bridges can expire in a shorter time than the estimated time due to many factors such as strong winds, earthquakes, heavy tonnage vehicle loads, vehicle crashes etc. Small cracks/damages that may occur due to corrosion and fatigue effects, especially in steel elements, may increase over time and cause sudden breakages. It has been seen in the past years that hangers, which are one of the slender structural elements, can break with the tearing of the plates, especially at the hanger-deck connection points. The creation of various damage/accident scenarios during the design of these structures, which are of high importance in terms of both the country's economy and life safety, will enable quick decision-making during possible events. For this purpose, scenarios for different loading condition and different number of hanger breakage situations were created for the Osmangazi Suspension Bridge with a main span of 1550 m, which was put into service in Turkey in 2016, and progressive collapse analyses were made. The ana-lyses, which was started by removing only one hanger, taking into account the dead load and dead load + vehicle load of the bridge, continued until the bridge collapsed. After each removed hanger, the internal force and displacement values of the hangers, cables, deck and towers of the bridge were obtained and compared with each other. The results obtained show that large force and displacement values occur in the field where the hanger is breakage, but the other parts of the bridge are not affected by this event. As the number of hangers breakage increases, the tensile strength of the hanger immediately adjacent to the hanger breakage may exceed the ultimate tensile force that the hanger can bear. This situation causes the hanger to start to break auto-matically and the bridge to collapse.

Automated summary

The design life of suspension bridges can be shortened due to factors such as strong winds, earthquakes, heavy vehicle loads, and corrosion and fatigue effects. This study focused on creating different damage scenarios for the Osmangazi Suspension Bridge in Turkey, and conducting progressive collapse analyses. The results showed that increasing the number of hanger breakages can lead to the collapse of the bridge.