Mechanical Response Characteristics And Fire Resistance Limit Of Marine Platform Structure Subjected To Local Fire

Offshore plateform as a production,living,national defense as one of the multifunctional offshore facilities.Because of the particularity of its working environment and the characteristics of internal layout,it is easy to cause local fire and explosion under external action,resulting in serious loss of personnel and property.Therefore,the study of structural response characteristics and fire resistance limit of marine platform under local fire can provide a basis for enriching the theory of structural safety design of marine platform.It provides theoretical support for the further analysis of the residual bearing capacity of the whole structure of marine platform under fire,and plays an important role in the further development of fire resistance theory of marine platform structure.The FDS model and ABAQUS model of offshore plateform room are established,the temperature field evolution law of offshore plateform room under local fire is studied,the fire resistance limit and failure characteristics of offshore plateform room under different fire scenarios are studied,and the fire resistance limit and failure characteristics of offshore plateform room under complex sea condition and local fire coupling condition are studied.The distribution characteristics of inhomogeneous temperature field and stress and strain of room structure in offshore plateform room under different working conditions are obtained,and the fire resistance limit and failure characteristics of offshore plateform under different working conditions are analyzed.The following research results are obtained:By using numerical simulation method,the room model of ocean platform is established to obtain the distribution of temperature field in the room under different conditions and coupled with wave load to obtain the structural stress and strain mechanical properties data under the combined action of the two.The results show that the deformation of the top floor and the bottom floor is mainly determined by the higher temperature field in the initial stage of the fire,and the trend of fluctuation with the external wave load appears in the later stage of the fire.In the whole process of fire development,the surrounding steel wall has a trend of variation with external wave load.At the same time,the amplitude change of the external wave load will affect the maximum displacement,and the larger wave load amplitude will produce a larger displacement value.The response characteristics of the structure under the different fire scenarios are discussed,and the influence law of the different fire scenes on the structural fire resistance limit and damage features is revealed.The results show that the displacement value of the surrounding wall is small and changes with the temperature in the room.The fluctuation of the wave load is also affected by the temperature value;the excessive displacement of the bottom floor displacement value gradually increases with the temperature,but no damage exceeds the ultimate deflection;the failure time of the roof floor is negatively related to the fire development coefficient of the fire source.The response characteristics of the structure under different complex sea conditions and fire temperature field are discussed,and the influence of complex sea conditions on the fire resistance limit and failure characteristics of the structure is revealed.The results show that the difference of boundary force in the initial stage of fire is not more than 10% under different sea conditions,which leads to no large deformation difference in the structure under each working condition.The amplitude of wave load varies obviously under different sea conditions,which makes the axial force gradient of each boundary of the ocean platform room different.The higher the sea condition grade,the higher the amplitude of the external wave load and the increase of the boundary force gradient,which leads to the advance of the limit displacement of the structure.The above conclusions can be used for structural safety assessment and fire resistance reinforcement design of marine platform.