Dynamic Response Analysis For Piled Wharf Structure Against Accidental Vessel Impact

Piled wharfs have been widely used in the muddy coasts by virtue of simple structure,rapid and convenient construction,high bearing capacity and foundation adaptable.During normal operation,a wharf is at risk for vessel collision incidents,the consequent lateral loads inherently are accidental load.At home and abroad,there have been several such incidents,causing great economic losses and casualties.Although the probability is small,the magnitude of impact load is very large,therefore,the situation must be taken into account in the structural design.Load Code for Harbor Engineering(JTS 144-1-2010)only defines the formula for calculating impact force during the normal berthing of vessels,that is low speed and under buffer fender.There are few research in the field of wharf structures under vessel collisions.After doing a literature review,the similarities between bridge piers anti-collision and wharf structures under vessel collisions are found.Both subject area involves structure-pile-soil interaction and other key issues,and many research achievements are adopted by the specification for vessel collision design of bridges.Use of static analysis and design procedures fails to account for important structure-pile-soil interaction and dynamic effects present in an impact event.FEM is a good way to solve the impact problem,it will produce accurate results with pile-soil interaction in consideration.With increasingly sophisticated theoretical calculations,finite element software has been greatly improved,can accurately simulate the structure response under vessel collision,getting the results of stress,displacement and time history of many other variables.In this study,a model of piled wharf subjected to vessel collision is developed with ABAQUS.This thesis has completed the following work:(1)Through literature,a more comprehensive understanding of the structure-pile-soil interaction and collision between structures and vessels is got.(2)Some theories and problems frequently met in proceeding of collision simulation are described,these are system damping,algorithm and convergence achievement tips of contact,types and settings of boundary condition,rational element size,etc.a FEM model of a single pile is created.According to the physical model,the FEM model is carefully calibrated by adjusting many parameters,ensuring a correct analysis technique is adopted,and most parameters are rational.This step will pave the way for further work.(3)A high-resolution finite element model is created.Some characters like: plastic response of soil,gap and slide between pile and soil interface,the effect of group piles are taken into consideration.Impact force-crush depth curve,time histories of impact force and displacement are extracted.(4)The impact force are calculated using both domestic and foreign anti-collision specifications.The results show that the domestic specification underestimates the response greatly,mainly because the elastic deformation coefficient is recommended to take a fixed value under the condition of the lack of experimental data.By conducting multiple numerical collision experiments,the elastic deformation coefficient values is calibrated,which expands the application scope of the specification.