Challenges in seismic design of incrementally launched bridges of Northern Marmara Motorway

This paper presents the challenges in the seismic design of the incrementally launched bridges of the Northern Marmara Motorway project in Istanbul Turkey. First it describes the initial design for these viaducts, then it presents the alternative design based on incremental launching method (ILM) and finally does a comparison of their performances. Regarding the earthquake resistance studies, traditional multimodal response spectrum analysis was carried out. This was then completed by a nonlinear time history analysis considering the behaviour the fluid viscous dampers, the cracking of concrete and steel rebar yielding at the plastic hinges. The results of these two analyses are compared in terms of forces and displacements, indicating the conservatism of the modal spectral analysis.