Study On Ultimate Capacity And Collapse Mechanism Of Offshore Steel Structures Under Super Typhoon

Typhoon is a kind of serious tropic cyclone which is very devastating. With the exhaust ofoil and gas on land, the working focus of exploration and exploitation about oil and gas isremoved from land to ocean, even more from epicontinental sea to deep sea, however therealiability of oil equipments have to undergo some accidental loads such as typhoon.Because of the huge volume, complex structure and high price of offshore structures, it ismeaningful to take a reseach on jacket platform progressive collapse to improve the capabilityagainst extreme loads and to ensure the integrity and reliability of the platform. The mainresearches and achievements include:(1) This paper established the finite element derrick model and made dynamic analysis to it,including modal analysis and wind-induced vibration response analysis. In these analysis, wetook advantage of the fluctuation wind speed spectrum Davenport to determine fluctuationload spectrum and random wind load-time history both in typhoon condition, used thetransient analysis solution module in ANSYS to analyze the dynamic response of the derrick,and determined the maximum displacement and stress response locations.(2) Considering pile-soil nonlinear coupling, it established the overall finite element modelof jacket platform using the large structural finite element software ANSYS, which includedtopside modulus, jacket and legs of the platform, and took static analysis under8kinds ofworking conditions to determine the maximum displacement and stress response locations.(3) Based on material nonlinearity and geometric nonlinearity, this paper assessed thewhole jacket platform’s ultimate bearing capacity under condition of no environmental loadand reference environmental load, and analyzed the environmental load influence on ultimatebearing capacity.(4) Referring structural progressive collapse prevention standards and scholar’s researchresults both at home and abroad to determine the collapse criterion of jacket platform, tookboth nonlinear static analysis and nonlinear dynamic analysis on topside modulus todetermine the load dynamic magnification factor, took component demolition method andPushover method to analyze the progressive collapse of topside modulus and derricks respectively, and further to determine the critical magnification factor of structure collapseand judge the progressive collapse prevention ability of the structure.