| In recent years,the high piled wharf has become the common structure form in inland river wharf,compared with other forms of inland river wharf,the high piled wharf's durability is relatively poor.In the long-term use of inland river high piled wharf,under the influence of environment,load and other factors,the reinforced concrete is easy to produce concrete carbonation,steel bar rust and so on,which lead to the decrease of resistance with time,so it is of great significance to study the time-varying reliability of wharf structure.Based on the engineering example and the characteristics of the inland river slab-beam type high piled wharf,the paper studies the time-varying reliability of the main structure of the wharf superstructure(track beams,cross beams,panels)and the structural system,the main contents are as follows:(1)By comparing various fatigue models,the S-N fatigue strength model is applied to the steel bar,and the limit state equation of fatigue is based on Miner's Linear Damage Accumulated Rule;by comparing the analysis method and calculation method of time-varying reliability,the reliability of each time period is analyzed by using time discretization method and calculated by the JC method.(2)Based on the analysis of the environmental factors affecting the superstructure of the wharf,the paper establishes the concrete carbonation model and the steel corrosion model of the initial service stage,the concrete carbonation stage and the reinforcement rust expansion stage.The resistance attenuation models of the track beams,the cross beams and the panels are established in according to the characteristics of each stage.(3)By analyzing the load factors affecting the superstructure of wharf and combining the resistance attenuation model of each stage,the time-varying functions of the track beams,cross beams and panels are established in three stages.The track beams bears the load of the portal crane,it belongs to the high cycle fatigue load,uses the finite element software Ansys to carry on the dynamic analysis to the track beams,extracts the moment-time curve of the dangerous section of the beams,uses the rain-flow counting method to identify the bending moment cycle of the fatigue damage,and builds the fatigue time-varying functions of the track beams.The cross beams and panels are subjected to large bending moments,and the resistance and load are considered as stochastic processes,and the bending time-varying functions of beams and panels is established.The reliability index of component is calculated by using JC method through MATLAB programming.The results show that: whether they are track beams or cross beams or panels,the corrosion time of steel bar is an important time node of structural reliability decline,the main reason for the decrease of fatigue reliability of track beams is the decrease of fatigue strength of corroded steel bar,and the main reason for the lower bending reliability of cross beams and panels is that the section area of corroded steel bars decreases.(4)Based on the theory of system reliability,the correlation analysis of the functions of the track beam,cross beam and panel are made,the correlation theory of non-linear functions is used,the PNET method is employed to find the representative component of different time period,and the time-varying reliability of the structure high-level correlation in the whole service period,the track beams and the cross beams and the panels belong to the low-level correlation;the reliability degree of the superstructure system is similar to the representative component at any time,so the reliability of the representative component can be approximately substituted for the reliability of the structure system. |
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