Analysis Of Anti-ice And Anti-seismic Performance Of Self-resetting Offshore Platform Based On Built-in Tubularrubber-tubular Double-wall Hollow Rocking Column

The vast majority of oil and gas resources in China come from offshore areas.The basin with the largest proven oil reserves in China is the Bohai Basin,with reserves of about 1 billion tons.Because of its special geographical environment,offshore platforms are often subjected to environmental loads such as wind,wave,current,ice and earthquake.These dynamic loads pose a great threat to the normal use and safety and durability of platforms.Therefore,it is particularly important to reduce the vibration response of offshore platforms under extreme loads.In view of the offshore platform structure system based on swing column,swing column external single direction only provide lateral resistance and the ability to reset,at the same time in order to increase the energy dissipation capacity,put forward to replace external swinging column with built-in steel pipe-rubber-steel pipe swaying double-wall hollow column,under external load,the lateral deformation of offshore platform driven steel tube and rubber produce shear deformation and energy dissipation,hysteresis At the same time,the built-in swing column can resist the load in all directions of the Marine environment of the offshore platform at the same time,which greatly reduces the number of swing columns and thus reduces the cost.Based on the structure form of JZ20-2 tubular scaffold offshore platform in Bohai Sea,this paper proposed a new type of structure based on double-skin rocking column with built-in tube-rubber-tube.(DSRC)and a self-reset offshore platform based on built-in self-reset swing-column was combined with prestressed cables.The anti-ice and seismic performance of the offshore platform under extreme ice load and large earthquakes was analyzed by ABAQUS.The main research contents of this paper are as follows:1、The finite element software ABAQUS is used to perform low-cycle reciprocating loading analysis on the built-in swing column to study its hysteretic energy dissipation characteristics.The hysteretic energy dissipation analysis of 8rocking columns with different outer tube diameters and different rubber layer thicknesses was carried out,and the key factors affecting the damping energy dissipation of the rocking column were obtained.2、Taking JZ20-2 jacket type offshore platform as an example,an offshore platform structure system based on built-in steel tube-rubber-steel double-wall hollow rocking column(DSRC)is proposed.The finite element software ABAQUS is used to establish a full-scale model of the offshore platform.Under different built-in rocking column parameters,the damping effect of the offshore platform in squeezed ice and bending ice,the displacement and acceleration damping effect under squeezed ice can reach up to 75% and 68%,and the displacement and acceleration damping effect under bending ice The highest can reach 72% and 51%.3、Tianjin wave,Taft wave and El-Centro wave were used to conduct seismic time-history analysis on the offshore platform based on the built-in DSRC rocking column,and the seismic effects of the rocking column under different steel pipe diameters on the offshore platform were compared and analyzed.The results show that the built-in DSRC rocking column has obvious effect on controlling the interlayer deformation of the offshore platform under earthquake action.Under the action of Tianjin wave,the peak displacement and peak acceleration are reduced by 47% and29%,the Taft wave by 53% and 31%,and the El-Centro wave by 46% and 15%.4、The prestressed cable is combined with the built-in steel-rubber-steel double-wall hollow swaying column to analyze the anti-ice performance of the offshore platform under extreme extrusion ice and bending ice based on the built-in self-reset swaying column,and the influence of the prestress value of the cable on the vibration damping effect of the offshore platform is analyzed.The peak displacement and peak acceleration at the key nodes of the platform are reduced by 78% and 62% at most under the extreme compression ice load,and the peak displacement and peak acceleration at the key nodes of the platform are reduced by 80% and 74% at most under the extreme bending ice load.At the same time,the prestressed cable can significantly reduce the residual deformation of the offshore platform and improve the self-reset performance of the structure.5、The seismic analysis of Tianjin wave,Taft wave and El-Centro wave under large earthquakes(seismic peak acceleration 620Gal)was carried out for the offshore platform based on built-in self-reset swing-column.Meanwhile,the residual deformation and self-reset performance of the original offshore platform under large earthquakes were compared.The results show that the maximum peak displacement and peak acceleration of the offshore platform under the Tianjin wave earthquake are reduced by 57% and 45%,the maximum peak displacement and peak acceleration of the offshore platform under the Taft wave earthquake are reduced by 48% and 29%,and the maximum peak displacement and peak acceleration of the offshore platform under the El-Centro wave earthquake are reduced by 52% and 25%.