Random dynamic response of a tethered buoyant platform production riser     

E.U. Etok  C.L. Kirk 《Applied Ocean Research》1981,3(2):73-86

A new normal mode spectral analysis method is presented for calculating r.m.s. riser deflections, bending stresses and lower ball joint angles. Forces on the riser consist of: (a) non-linear fluid drag taking account of the relative velocity due to tethered buoyant platform (TBP) motion, riser elastic deflection and wave induced fluid velocity, (b) wave induced fluid acceleration, (c) inertia forces due to TBP acceleration, and (d) buoyancy. The non-linear fluid drag forces are linearized using Tung and Wu's approximation based on the r.m.s. relative fluid velocity and current. A wide range of results is presented for risers in water depths up to 1000 m and it is observed that 6 normal modes are sufficient for calculating bending stresses. A static analysis is also presented for bending stresses due to wave and current induced drag forces and riser offset.  相似文献   

Dynamic and static analysis of a marine riser   总被引：1，自引：0，他引：1  

C. L. Kirk  E. U. Etok 《Applied Ocean Research》1979,1(3):125-135

A frequency domain normal mode solution is presented for the dynamic response of an unbuoyed marine riser subjected to periodic excitation from a surface vessel in the direction of wave propagation. The variable tension beam-column equation is solved in terms of normal modes of free vibration of the riser and the rigid body displacement. Drag forces on the riser are represented by Morison's formula taking account of the velocity of the riser and wave-induced fluid velocity. A periodic solution for the flexural motion of the riser and the bending stress is then obtained by means of an iterative solution of the frequency response function. The drag force induced stresses arising from a linearly varying current are also determined. The results presented compare favourably with those obtained by other methods.  相似文献   

Wave induced random oscillations of pipelines during laying     

Colin L. Kirk  Essien U. Etok 《Applied Ocean Research》1979,1(1):51-60

A study is presented of wave induced random vibrations of pipelines suspended in the $\text{J-}\text{configuration}$. The analysis is based on the use of Morison's equation for the hydrodynamic forces and a linearized spectral analysis of response in the first five normal modes of oscillation. Three pipelines are studied for an operational sea state of $\text{H}{}_{\mathrm{S}}\text{= 4.57}\text{m}$ and a survival case of $\text{H}{}_{\mathrm{S}}\text{= 12}\text{m}$. Extensive results are given for the expected peak deflections and stresses. Under operational conditions the expected peak stresses were found to be well below the maximum allowable stress for both the pipeline and the concrete coating, but in the survival case the peak stresses were found to be unacceptably high.  相似文献