The Anti-ice Capacity And Aseismic Capacity Analysis Of Jacket Type Offshore Steel Structures

Steel jacket offshore platforms are widely employed in offshore petroleum activities throughout the oceans of the world. As the offshore structure located in a seismically active region, the environmental loads are very complicated and harsh. And the earthquake ground motion becomes an equally important design load of structural excitations as well as the sea waves. The ice-induced vibration of ice-resistant Platforms is quite intensive, and directly endangers the structural safety. Therefore, it is necessary to study the anti-ice and seismic of offshore platform.The main contents of this paper are as follows:(1) This paper systematically introduce the offshore environmental loads and additional factors, and all kinds of ice loads are summarized.(2) The effect of the static ice load and dynamic ice force on the Jacket offshore platform is taken into account. That is, the analysis of anti-ice safety assessment and ice-excited vibration has been studied when the control loads ultimate capacity analysis is blocking ice.(3) The seismic analysis of offshore platform is discussed. In this paper, a jacket platform of Bohai Sea was taken as a case study. Pushover analysis was adopted for the study of its seismic behavior under earthquake. Target displacement was determined with capacity spectrum method. Nonlinear time history analysis was conducted under the same earthquake. And it is also illustrated that pushover method can be employed to assess seismic vulnerability of jacket platforms by comparison of structural capacity spectra between dynamic time history analysis method and push-over analysis method. All of above will be useful for earthquake-resistant performance decision in practical jacket platform structure.(4) Impact analysis of damage and flaw on anti-ice capacity and aseismic capacity of jacket type offshore steel structures is studied. In service period jacket offshore platform structure maybe existing damage and flaws, such as cracks, sink marks and corrosions. Besides, the structure may be influenced by sea organism attachment and foundation erosion. All those will reduce the strength of structural members or enlarge the environmental load, so as to reduce the bearing capacity of the platform. In this paper, a jacket platform of Bohai Sea was taken as a case study. Analysis was adopted for the study of damage and flaw on Anti-ice capacity and seismic capacity of jacket type offshore steel structures, by comparing of the response under dynamic ice force, ice resistant capacity spectrum, remaining strength accumulation coefficient of the structural and seismic response before and after injury, and taking three seismic waves to make a comparison of the seismic response, seismic capacity curve, structural seismic safety margin coefficient, we have obtained the impact analysis of damage and flaw on anti-ice capacity and seismic capacity of jacket type offshore steel structures.