Time-dependent Reliability Analysis Of Barge Anchor Chain Based On Series System

For Port Engineering structures, anchor chain affected by wind、current and someother environment factors in its design life which led to structural erosion, furthermore,this make its resistance drops and cause safety problems. In general, we consider theerosion rate of the whole anchor chain is the same, however, the whole anchor chain’serosion rate is different in practice, which means using the single erosion rate can notreflect the impact caused by erosion to the anchor chain. For the problem, consideringthe situation that anchor chain’s erosion is different in different engineeringenvironment, assume the anchor chain composed of several single segments, buldinganchor chain series system model, analysis the time-dependent reliability of anchorchain. Besides this, considering the change of mooring force lead to fatigue failure ofanchor chain, compute the fatigue life of different anchor chains in different stochasticprocesses and analysis the fatigue reliability of anchor chains. Main contents andconclusions are as follows:(1) For the problem that anchor chain’s erosion is different in different engineeringenvironment, combine with existing structural erosion power function model, set up aseries system model which is applicable to describe the problem of anchor chain erosion.Analysis the time-dependent reliability of mooring linr in Chongqing based on thesituation that its resistance drops each year caused by erosion. The result shows that theterritorial waters anchor chain is the most dangerous part, the open bow anchor chainand open stern anchor chain is safe. At the same time, the computed results also showswhen treat a anchor chain as a series system, the more chain a anchor chain contains, thelower resistance it has.(2) Based on existing hydrological data, computed the force of anchor chain in differentstochastic processes，selected the annual maxima mooring force of each barge anchorchain. Weibull distribution and P-Ⅲdistribution are used to fit with the arch annualmaxima mooring force.(3) Considering the change of mooring force lead to fatigue failure of anchor chain,based on Miner linear cumulative damage theory and rainflow counting method,calculated cumulative fatigue damage and fatigue life of different anchor chain indifferent stochastic processes within design fatigue life. Based on the computed resultsand considering the stochastic factors, analyzed the fatigue reliability of different anchorchains in each worst stochastic processes. The results shows that the size of mooringforce acting on anchor chain is great important factors about structural cumulativefatigue damage. The larger the mooring force is, the higher the cumulative fatiguedamage are and the greater the probability of fatigue failure is. The smaller the mooringforce is, the lower the cumulative fatigue damage are and the lower the probability offatigue failure is.