Research On Fragility Curves Of High-Piled Wharf Subjected To Horizontal Loads

High-piled wharf is an important wharf structure which is widely used in coastal area and Yangtze River area. Ship collision load is usually the controlling horizontal load in design. In recent years, there has been a lot of high-piled wharf-ship collision accidents resulting in huge losses, therefore, it is necessary to evaluate the fragility of wharf structure in order to assess the danger of wharf subjected to ship collision loads. The displacement ductility ratio is adopted as pile damage index, and the damage status of high-piled wharf is determined in this way. A high-piled wharf is taken as the prototype, and ANSYS is used to simulate the structures. The modals of high-piled wharf is analyzed, and the theoretical fragility curves of single bent structure and spatial structure subjected to horizontal loads are researched respectively. Bending fixed point method and contact element method are adopted to consider pile-soil interaction, the fragility curves of single bent structure and spatial structure are compared. The fragility curves in this paper can play an important role in determining the damage probability of high-piled wharf structure subjected to corresponding horizontal collision loads of ships with different tonnages, which can be a reference for structure design and safety monitoring of high-piled wharf.(1) The modal analysis is carried on for high-piled wharf, and the natural vibration frequencies of the first six order modal are obtained, which can be used to avoid resonance resulting from external excitation with certain frequency.(2) The pile top displacement ductility ratio is adopted as pile damage index, and the relationship between the damage status and the damage index is researched. Based on series model theory, the damage status of high-piled wharf is determined by the damage status of piles.(3) The structure fragility analysis is carried on for high-piled wharf subjected to horizontal collision loads. The ship collision load is simplified as a uniform force on the wharf, and single bent structure and spatial structure finite element models are built. The fragility of structure subjected to ship collision loads is analyzed and the structure damage probability corresponding to ships with different tonnages.(4) For the finite element models of single bent structure and spatial structure with considering pile-soil interaction by contact element method, the pile body horizontal zero displacement point of plumb pile is approximately 13 m from pile top in vertical direction, in other words, the zero displacement point is about 3 m or 5 times of pile section width from soil surface.(5) The parameter analysis is carried on for high-piled wharf subjected to ship collision loads, and the fragility curves of high-piled wharf subjected to ship collision loads are established. The fragility curves of single bent structure and spatial structure with considering pile-soil interaction by bending fixed point method and contact element method are compared, and the fragility corresponding to the same ship tonnage obtained by bending fixed point method is relatively greater.