Safety Performance Of Jacket Platform Considering Corrosion

Offshore structures are in a very complicated ocean environment and they shall undergoseveral types of environmental loadings,including winds,waves,earthquakes,and suffer other damage caused by corrosion.Ocean corrosion will not only cause serious damage to the offshore structures,reduce its strength and resistance to external load capacity,it will also cause disaster events,such as collapse to the staff's production and hidden trouble to safety.Currently,the safety analysis of marine structure is mainly aimed at the structure designed but rarely has the consideration of corrosion damage.However,the existence of the corrosion damage would be a threat to the safety of the structure,so it is necessary to consider the security performance of the corrosion of offshore structures.In this article,corrosion test,monotonic load test and cyclic load test are applied.After the analysis,the stress-strain relationship models of steel NV-D36 are determined.Based on these relationships,the influence of corrosion damage to the safety of the offshore structures is studied.The specific research contents are as follows:Referring to the electrochemical corrosion test,monotonic load test and cyclic load test,finds that the changing rules of the NV-D36 tensile properties were mentioned as followed: as the corrosion degree deepens,the elasticity modulus,yield strength,yield strain,ultimate strength have a downward tendency.While under the cyclic loadings,the hysteretic curves of NV-D36 steel are very full and spindle shaped,which shows that this kind of steel has a strong plastic deformation capability and good seismic performance.What's more,as the corrosion degree deepens under the cyclic loadings,the stiffness of NV-D36 has no change but the strength changes a lot.Three corrosion modified stress-strain relationship models of NVD36 were set up.By fitting the data obtained from the tension tests,a triliner corroded stress-strain relationship model contains elastic segment,yield plateau and hardening segment was calibrated,therefore,an exact triliner corroded stress-strain relationship will present if the corrosion degree is known.Fit the data obtained from the cyclic tests to obtain corrosion modified Chaboche model and Steel01 stress-strain relationship model.All the models mentioned above can be applied to numerical simulation software.The safety performance of the jacket platform structure was analyzed.Use the traditional section subtraction method and corrosion modified model method proposed in this paper,these two methods,to pushover the jacket platform structure and obtain the strength reserveratio,ductility coefficient,and plastic rate when platform collapses which change with different platform corrosion degree.The seismic performance of the jacket platform structure could be analyzed by using these two methods,and the influence of corrosion damage on the seismic performance of the structure was obtained.Co MParing the analysis of two kinds of methods for corrosion damage when calculating the jacket platform security,found that using traditional section subtraction method it will overestimate the technical specifications of the jacket platform,such as strength reserve ratio RSR,ductility coefficient and plastic rate of the collapsed offshore,etc.