Abstract- Celep MSc.
SEISMIC PERFORMANCE ASSESSMENT AND RETROFIT OF THE ORTAKÖY VIADUCT (V408)
U. Utku Celep
(Thesis Supervisor: M. Nuray Aydınoğlu)
The Ortakoy viaduct is one of the approach viaducts of the Atatiirk suspension bridge, which plays an important role as a lifeline in Istanbul. The bridge was designed in 1968 and shows specific features of the pre-1971 seismic design methodology, lacking ductility and adequate detailing. Visual inspection of the bridge shows that, extensive corrosion of the longitudinal and transverse reinforcement is common at most column bases due to the lack of maintenance considerations. The performance of the bridge has been assessed with displacement based procedures by using pushover and nonlinear time history analysis tools. Analysis results indicate that elastomeric bearings are highly susceptible to failure in both orthogonal directions of the bridge and high ductility demands develop particularly at Bent 4 and Bent 5. Target performance criteria have been developed and two retrofit strategies have been proposed in order to enhance the seismic behavior of the bridge. In the first strategy lock-up devices has been used in conjunction with shear keys. Analyses results indicate that the first strategy is not as sound as expected. Crescent moon-shaped steel hysteretic dampers have been used in the second strategy. Satisfactory results have been obtained in the second strategy where much refined results is likely to be obtained with more detailed analyses.