The Research On Key Technologies Of Composited Wharf

With the rapid development of the national economy,the foreign trade and import demand for raw materials increase significantly in China,which accelerates the construction of large-tonnage(30-50 million tons)open-type deep water wharf.The structure type of the wharf is more diversified and the reason of choosing this type of wharf is not only related to the safety of the wharf,but also due to the significant economic and social benefits.According to the two types of wharf structures(i.e.,gravity type and high-pile type)which are widely used in China,Enzong Niu,a design master from China Communications and Water Transportation Planning and Design Institute,proposed a new composited wharf structure type.This new composited wharf structure combines the advantages of both gravity and high-pile wharfs.However,due to the innovation in the structural form,there are still some key issues to be solved urgently,especially the connection between steel pipe piles and concrete caissons,i.e.,the pile foot joint.In this paper,a new kind of embedded pile foot was designed,and some key problems of the composited wharf structure were studied.The main contents include:(1)The state of art of all types of wharf structures was first introduced,and the major properties of this new composited wharf structure were analyzed.The conditions whether to construct this structure form of wharf were discussed.(2)A comprehensive review on the design methods of all kinds of pipe foot joints was then carried out.According to the mechanical characteristics of the batter-piles which are the main structure component of this composited wharf,a design method of the embedded pile foot was proposed.(3)A series of experimental studies on the mechanical performance of the tensile,shear and tension-shear combination of the embedded pile foot anchored with large diameter steel bars were conducted.Three sets of specimens with large diameter anchor bar under the action of tension,shear and tension-shear combination were designed and tested.The failure modes of the specimen were obtained,and the test results were compared with that of specimens anchored with small diameter steel bars in existing studies.The comparison shows that the existing predicting models of the shear capacity for the embedded pile foot anchored with small diameter steel bars were not suitable to predict the shear capacity of the embedded pile foot anchored with large diameter steel bars,while the existing pull-shear relationship model is capable of simulating the pull-shear relationship of the embedded pile foot anchored with large-diameter steel bars.(4)A numerical analysis of the shear resistance of the embedded pile foot joint was carried out.A finite element model was established to calculate the shear capacity of the joint.The calculated results are in good agreement with the test results,which show that the established finite element model has a good accuracy.The internal force distribution of the anchor plate and the anchor bar was then obtained by the finite element method.The shear mechanism of the joint was analyzed(5)An experimental study on the mechanical performance of wharf structure composited by batter-pile base connection was carried out.Two specimens of batter pile structure are designed to simulate the stress state of the foot joint under the horizontal load.The failure mode of the specimens was obtained and the structural performance was discussed.The mechanical properties of the batter-pile structure together with foot joint were analyzed.(6)An finite element simulation for the structural performance of the batter-pile structure was carried out using the finite element software ANSYS.The deformation of the structure,the internal force of the steel pipe,the reactions of the pile foot joint and the stress distribution of each component were obtained.Based on the simulation results of finite element analysis,some design points of batter-pile structure were proposed.