Seismic Fragility Analysis Of Steel Pipe Pile Wharf Damaged By Random Pitting

In the field of wharf engineering design,the mainstream foreign standard codes have adopted displacement-based seismic design methods,while the domestic forcebased design codes of "Water Transport Engineering Seismic Design Code"(JTS146-2012)are still used,failing to reflect performance-based Anti-seismic design concept.In addition,the chloride ion erosion in the marine environment will cause damage to the structure and affect the seismic performance of the structure.How to describe the degree of corrosion of the structure is a problem worthy of study.In view of the above problems,this paper considers the different degrees of rust damage of the wharf structure,and analyzes the seismic vulnerability of a typical high-pile wharf structure.The main research contents of this article are as follows:1)This paper considers the uncertainty of the objective natural rust phenomenon and uses the stochastic process theory to describe the rust.First,an algorithm for generating a random pitting corrosion model is proposed and the stress-strain curve of Q345 steel is obtained according to the uniaxial tensile test.Based on this,200 random pitting damage finite element models of uniaxial tensile specimens are constructed and expanded Non-linear analysis to study the degradation law of yield strength and ultimate strength of specimens under various pitting strengths,pit depths and pit radii;linear regression analysis based on sufficient samples to explore the fracture position of steel with pits;According to the random process theory,the yield strength and ultimate strength of the pitting damage structure are predicted.Finally,the Gamma model is used to obtain the probability degradation model of the yield strength and ultimate strength of the pitting damage structure,that is,the probability density with the volume loss rate as the independent variable function.2)Considering the pile-soil effect,based on the OpenSEES computing platform,a three-dimensional finite element model of a high-pile wharf structure consisting of five rows of steel pipe piles and multilayer soil seabed soil is constructed,which mainly simulates the seismic response of the structure and geotechnical system.This paper also uses existing experiments to verify the pile-soil model.The content of dynamic time history analysis includes: displacement and acceleration response of each elevation position of the soil layer on the sea side and the land side,pile top(deck)displacement,pile body displacement,pile shaft force,pile shear force,pile bending moment,The curvature of the pile section,the acceleration response of the pile body and the residual displacement after the earthquake.3)Considering the uncertainty of ground motion and the uncertainty of material performance caused by random rust,based on the probability model of strength degradation of rusted steel obtained above,the ground motion-structure samples are generated corresponding to different rust rates,and the probability seismic demand model of the structure is established.The peak ground acceleration(PGA)is selected as the ground motion strength parameter,the deck displacement ductility coefficient and the steel pipe section curvature ductility coefficient are used as the structural damage parameters,the seismic vulnerability analysis of the wharf structure is considered considering the influence of corrosion,and the structural seismic vulnerability curve is drawn The probability and degree of damage to a structure when it is subjected to an earthquake disaster of a certain intensity.The paper has 70 figures,24 tables,and 106 references.