Research On Risk Assessment Method To Rate Typical Hazards Of Pile-supported Wharf During Operation Period

The wharves are fraught with various safety hazards.Taking targeted risk control measures based on scientific and effective risk assessments improves wharf safety.Common risk assessment methods rely on subjective judgments entirely.Also,there is difficulty comparing hazards across different categories and singularity in terms of evaluation index system.In order to address these problems,a comprehensive risk assessment system of pile-supported wharf is established,and a corresponding method to rate hazards is put forward.The common hazards with serious consequences or high occurrence probability including earthquake,ship-load overloading,heap-load overloading and soil creeping are selected to be analysed.The proposed method is illustrated by a numeriacal example of a typical pile-supported wharf in Tianjin.In addition,a risk management software is designed to support the proposed method.The details are summarized as follows:(1)The risk assessment method to rate typical hazards of pile-supported wharf during operation period is put forward,which quantifies the risk by producting probability index and loss index.The probability index is defined as the failure probability of the structure,which can be calculated by integrating the product of proneness cumulative distribution function and vulnerability probability density function on the domain of the hazard factor for the hazards caused by external environment.The loss index can be generated by paired comparison according to GAHP method.(2)Regarding the earthquake hazard,PGA is taken as the intensity of hazard factor,and the seismic hazard proneness of the project site is analyzed based on the existing statistical results.Considering the uncertainty of seismic wave,the seismic demand response model of each pile is established by incremental dynamic nonlinear time history analysis,and the seismic vulnerability of the structure is determined according to the damage criterion of each pile.(3)Regarding the overloading related hazards,the overloading load is taken as the intensity of the hazard factor,and based on the code and the existing statistical results,the overloading hazard proneness of ship-load overloading and heap-load overloading is determined.Taking the excessive displacement of bent frame as the corresponding risk event,the critical load of random structural samples is calculated considering the randomness of material strength and size.Taking Newton Raphson equilibrium iteration non-convergence as the failure criterion of excessive displacement,the structural vulnerability of ship-load overloading and heap-load overloading is determined respectively based on statistical analysis.(4)Regarding the soil creeping hazard,the Singh Mitchell model parameters are fitted based on the previous test results to determine the shear strength degradation model of creeping soil.Considering the randomness of soil parameters,the safety factor of random samples corresponding to each wharf slope is calculated by strength reduction method.The distribution of the samples is determined,and the failure probability of the risk source of soil creep is obtained.(5)The risk management software is designed based on the proposed risk assessment method.The comprehensive risk assessment and ranking of the selected hazards are realized using the software,which proves the feasibility of the proposed risk assessment method.