We held a seminar in 2021 for the purpose of identifying and sharing current issues on seismic design for pile-supported wharves described in the technical standard and commentaries for port and harbour facilities in Japan revised in 2018, in collaboration with the National Institute for Land and Infrastructure Management (NILIM) and Japanese Technical Association for Steel Pipe Piles and Sheet Piles (JASPP). This technical note summarizes the discussions at the seminar in terms of viewpoints of research aimed at improving the seismic design methods for level 2 ground motions.
The main issues identified are 1) Performance requirement for level-2 ground motions of non-high-earthquake-resistance wharves (standard wharves) has not been defined, 2) The present method which counts the number of plastic hinges on the piles for the performance verification of level-2 earthquake resistance for the serviceability or repairability of high earthquake-resistance wharves does not correspond to the actual serviceability or repairability, and 3) Decrease in strength due to the exceedance of ultimate curvature cannot be expressed in the current numerical seismic analysis (i.e., FLIP) with the present relationship between the bending moment and the curvature. To assess these issues, it was suggested that safety should be specified as the performance requirement for level-2 ground motions of standard wharves. It was also suggested that performance evaluation should be made for the actual loads corresponding to expected transport of emergency supplies or freight on major shipping route that need to be maintained after the level-2 ground motions. We identified the necessity for specific researches on the performance verification methods that were consistent with the proposed performance requirements.
We will continue researches based on these proposed policies. Also, we will discuss other types of berthing facilities, considering the issues and policies identified for piers, so that we can improve the seismic design method for higher accuracy and efficiency.