Evaluation of optimal ground motion intensity measures and seismic fragility analysis of a multi-pylon cable-stayed bridge with super-high piers in Mountainous Areas

16 ground motion intensity measures (IMs) were utilized to assess the seismic performance of a multi-pylon cable-stayed bridge with super-high piers in mountainous areas. The best IM was identified based on the practicality, efficiency, proficiency, sufficiency and hazard computability, and was used to carry out the seismic fragility analysis of the bridge. Results show that peak ground velocity (PGV) is the best IM for such a bridge with super-high piers. By using the IM of PGV, the displacement components, such as bearings, suffer the greatest damage. In the case of large earthquakes, the damage probabilities, especially those exceeding the severe state, are very large for the longest cables. However, the possibility of the girder falling off the piers is very small. The transition piers are also seismically vulnerable. The pylons and super-high piers are not seismically vulnerable, although being the main vertical components and very tall. Therefore, the displacement capacity of bearings and the strength capacity of long cables and transition piers should be improved by taking seismic fragility into account.