Study On The Strengthened And Vibration-Absorption Of Gravity Platform In Shallow Sea Based On ANSYS

The new offshore gravity platforms designed for the specific situation of Bohaibay, of which seismic behavior of research is still in the theory research and designphase. At present, the seismic performance of the gravity platform has an initialtheory research. The results of the study show that the horizontal displacement of theplatform is very large under the effect of the seismic waves. So it is necessary toattach more importance on the study of an effective vibration control strategy for theplatform.The viscoelastic damper is an effective passivity seismic control device. It canreduces the seismic response of structure by adding the damping and dissipating theseismic energy of the structure etc. At the same time, the viscoelastic dampers havethe traits of economical and high reliability, and they can be easily installed. So it hasa broad application foreground in projects, and it has become one of the hot issueswithin the seismic fortification control techniques of the structures. Therefore, it’s ofgreat significance to apply viscoelastic dampers to the seismic research of offshoregravity platform.Based on the disadvantages and advantages of offshore gravity platformconsidering the aspects of structural seismic, this paper mainly does the followingwork:(1)At first, this paper explores the seismic behavior progress of gravityplatforms, and comes to a conclusion that the pillar torsion and deformation ofgravity platforms under earthquake is very big，thus make the whole platform’shorizontal displacement too large. And then the purpose and meaning of this studywas put forward.(2)For the deficiencies of the platform seismic behavior, the paper takes twomethods to control the platform’s big deformation: One is the traditional method bymeans of installing horizontal poles to improve the structure resistance, which canreduce the big displacement of the platform; Another is the effective passivity seismiccontrol device—the viscoelastic damper. (3)In the traditional method, according to the requirements of 《Specificationsfor the Construction of Fixed Platform》, three different sizes of the horizontal poleshave been demonstrated this paper to reinforce the platform, and studying the model’schange of the biggest displacement and stress respectively. The results show that thehorizontal displacement of the platforms have been obviously controlled by horizontalpoles, but the biggest stress of the platform have been remarkably increased, and theposition of the greatest stress is shifted.(4) In the study of effective passivity seismic control, above all, the originalplatform model were equiped with viscoelastic dampers at the places that the coulpingplaces between the columns and the deck as well as between the column and thecaisson, under the same accleration of the3D-ground seismic wave, and the analyticalresults showed that the damping effects are not so obvious and the displacement isstill very big when the platform was just installed viscoelastic dampers, but thebiggest stress became smaller. It’s just because that the paper used the method ofinstalling both horizontal poles and viscoelastic dampers to control the platform’sdeformation, and analysed respectively from the aspects of damper installationposition, installation angle, damper coefficients and installing quantity, then theresults concluded is that different damper installing position in platform effect shockabsorption, damper damping effects of slant supports is better than other style;Different damper installing angle in platform also has different damping effect,among them the45degrees installing angle exerts better effects at shock absorptionthan others; The number of the damper also has an impact on the shock absorptioneffects, the more dampers the better shock absorption effect, and when the number ofdampers is inceased to a certain number the shock absorption effects tend to bestability.The research results illustrate that viscoelastic damper can work well underunusual level seismic. At the same time, after the optimum design of the structurewith viscoelastic dampers, the platform structure’s seismic fortification ability ismarkedly improved.