The Research On The Reliability Of Offshore Structures Under The Random Attack

The reliability of offshore structures is not static, and structure strength and load have an important impact on the reliability of the structures system. The research on the reliability of offshore structures has attracted more and more attention increasingly. At the same time, the input of the research on the reliability of offshore structures increases continually. The reliability of offshore structures can be seen as multi-functions based on structure strength, load and so on as independent variables. The change of structure strength is related to the environment, and the load can be seen as the accelerated factor of the degradation of structure strength. The strength of structure and the size of load have obviously randomness, so it is truly difficult to assess the level of the reliability of the system of offshore structures with a single load level and a constant parameters of structure strength. Therefore, in order to get quickly the index of the reliability of the system with the change of the parameters and provide theoretical basis for designer, it is necessary to study the change law of the reliability of the system of offshore structures with the strength parameters, the load numbers and so on.The main results in this paper are below:From the consideration of the systems and components, this paper studies the change of the reliability of offshore structures with the change of the attack numbers and studies the reliability of structure strength from the aspects of degradation and nondegradation respectively. Including specifically the following aspects:(1) Improve the interference model of load-strength and the condition with the time change of the model. So that the reliability the structures has the parameters with the numbers of load,and study the reliability of structures from the static to the dynamic.(2) Present the effect of the random load of the small mean on the systems in several times, which is similar to the effect of the random load of the large average and the small discrete degree on the reliability of the systems. After it has the accumulation of the quantity, the load of the little impact on the systems has a qualitative impact on the offshore structures. The results which applied to the practice indicate that it is corresponding to the true.(3) Apply the calculation method jc to the reliability model which calculates the offshore structures under the attacking by n times.(4) Consider the strength change of structures when the structures strength degrades and the systems do not fail. Study the impact of the attack numbers on the structures strength on the basis of equivalent load, and the reliability of the systems and the size of attacks change.