| Under the marine environment,the aging and failure of reinforced concrete structures are very common,and the durability has become a problem that must be faced both for the built and new structures.During the service period,the performance of reinforced concrete structure will degrade over time.So,the static reliability analysis method is not reliable.It is necessary to study the structural dynamic reliability analysis method that the resistance changes with time.However,when considering the model of resistance deterioration of reinforced concrete,many scholars regard the coefficient of variation as a fixed value,and think that the mean and standard deviation of resistance distribution have the same time-varying law.In fact,the standard deviation of resistance may appear as an ever-increasing law over time.Assuming the same time-varying law of standard deviation and mean value,the calculated structural reliability may be larger than the actual value.In addition,although the time-varying law of the overall bearing capacity of the high piled wharf's transverse bent has been studied,only the impact force of the ship and the effect of heap load were taken into account,the load of the gantry crane was not considered.Based on these two issues,this paper carried out the following research work:(1)The degradation process of reinforced concrete structure in chloride environment is analyzed.The time-varying model of chloride ion diffusion model,steel corrosion rate time-varying model,concrete strength time-varying model and reinforced concrete bond strength coefficient are compared and selected.(2)Considering the steel corrosion and material deterioration of the structure during the reference period,a stochastic simulation method and a method of calculating the time-varying resistance of the reinforced concrete structure were established.According to the probability distribution of random variables,10000 sets of Monte Carlo stochastic simulations of the degradation process of the bearing capacity of each component are carried out.Through stochastic simulation,the probability distributions of the cross-sectional area of the reinforcement,the strength of the steel bar,the bond coefficient of the reinforced concrete and the resistance of the members at different moments are obtained.Based on this,the time-varying probability model and the timevarying probability model of component resistance,which influence the key parameters of component bearing capacity,were established by fitting the mean of probability distribution and the variation of standard deviation with time respectively.(3)A stochastic simulation method for the degradation of the overall bearing capacity of high piled wharf's transverse bent is established.The probability distributions of these three parameters at any time are obtained from the time-dependent probability models of cross-sectional area of corroded bars,strength of corroded rebar and bond coefficient between rebar and concrete.The parameters are sampled by PDS module in ANSYS software,and the sample values are imported into the parametric finite element model of transverse rack of piled wharf.Through the finite element calculation,the probability distributions of ultimate bearing capacity at 6 time points during the reference period are obtained.By analyzing the probability distributions of the sample data at different time points and fitting the time-varying law of the mean and standard deviation respectively,a time-varying probability model of the overall bearing capacity of the high piled wharf's transverse bent is established.(4)The calculation method of structural time-varying reliability based on the idea of section discretization is improved.Furthermore,the method is used to calculate and analyze the time-dependent reliability of the main components of the piled wharf and the overall structure of the transverse bracing,which verifies the feasibility of the method in the durability assessment. |
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