Buckling Propagation in Marine Pipelines

The buckling propagation in marine pipelines is studied by means of the cylindrical shell model in this paper. Several parameters including geometrical parameter D/ T, L/ D, physical parameter E and σy are discussed. The computed results are compared with the available experimental data and other computed results, it is found that the present results are closer to the experimental results than other computed results.     

Water Wave Refraction and Diffraction over Frictional Topography

- This paper considers the effects of wave energy dissipation induced by sea-bottom friction on the computational results of water wave refraction and diffraction with the parabolic equation method. The presented results show that the friction factor formula adopted in this paper is of higher numerical accuracy than that introduced by Dalrymphe (1984), and it can be used to compute wave propagation over large open areas.     

An Engineering Computational Method of Calculating Wave Forces on the Mat and Platform''''s Sit-on-Bottom Stability

- In this paper, an engineering method is employed to calculate the horizontal and vertical wave forces on the mat of the submersible platform under Froude-Krylov hypothesis. According to some model tests, appropriate diffraction coefficients are selected. And the results of the formulae given in the paper agree satisfactorily with those experimental data now available. The proposed computational method is effective and convenient to use in evaluating the horizontal and vertical wave forces on the mat. An exmaple is also given in this paper. Finally, the effects of the vertical wave force on the platorm's sit-on-bottom stability are analyzed.     

Dynamic Response of Fluid-Single Leg Gravity Platform-Soil Interaction System

- An approximate method is presented to investigate the earthquake response of the fluid-single leg (shortened for S. L.) gravity platform-soil interaction system. By assuming a suitable form of the velocity potential of the radiation waves and by using the motion equation and the boundary conditions, the unknown coefficients can be obtained. Thereafter the function of frequency for the interaction system may also be obtained. In this paper, the difference of the system dynamic response between rigid foundation is analyzed and the influences of the various foundation geometric dimension and the various water-depth on the hydrodynamic loading and dynamic response of the system is illustrated.     

Evalution of Application of p-y Curve Method in Offshore Engineering Foundation

- Based on the Mohr-Coulomb failure principle and Rankine's theory, the laterally loaded pile ultimate resistance formulas of sand and soft clay proposed by Reese and Matlock respectively are discussed in this paper. The authors put forward the modified ultimate resistance formulas on the basis of which the ultimate resistance formula is developed for horizontally loaded pile in multi-layer soil in consideration of the effect of the overburden soil pressure on the calculation of soil layer. It is significant to the correct application of the ultimate resistance formulas in API and ZCS Rules into offshore engineering.     

Trial and Numerical Analysis of Specimen Pipelay

Subsea pipelay has a relatively long history. In recent years, there has been a domestic need for the laying of large diameter thin wall pipes. A land-based trial for the large diameter thin wall specimen pipe is described in this paper. Re-gression analysis is performed for the trial data and the formula derived can express the trial data very well. Numerical analysis is adopted to compute various trial conditions. Then the numerical model is revised with the trial results, which are consistent with each other. After summarization of the results of trial and numerical analysis, the characteristics are described of the spatial configuration during the laying of the pipe and it is concluded that the maximum strain appears around the center of the raised pipeline. In the end, a reference Standard, which limits the maximum stress below the yield stress is provided.     

移动式海上基地多模块间相互作用对连接器载荷的影响

移动式海上基地(MOB)一般由多个模块构成,模块间的相互作用对连接器载荷可能有影响,但在许多现有文献中通常被忽略。计算了考虑模块间相互作用的5模块MOB的模块运动和连接器载荷响应,并与不考虑模块间相互作用的结果进行了比较。结果表明模块间相互作用对不同连接器刚度的MOB连接器载荷的影响不同,在浪向角较小尤其在迎浪时十分明显且不可忽略;当浪向角较大尤其是横浪时,模块间相互作用力较小。     

河口最大浑浊带形成的动力模式和数值试验

应用改进的ECOM模式,耦合泥沙输运模型,研究理想河口最大浑浊带形成的动力机制。河口最大浑浊带位于滞流点处,上下游余流均向该处输运泥沙,造成该处泥沙汇合,而由流场辐合产生的上升流又使该处的泥沙不易落淤。南岸(河口东向)的泥沙浓度比北岸高,最大浑浊带位于南岸,这是由于盐水入侵带来的高盐水位于北岸的底层,其斜压效应使底层的环流由北向南流动,把底层高浓度的泥沙向南岸平流,聚集于南岸底层。除上游河流泥沙来源外,强大的涨落潮流冲刷床面,使沉降于床面的泥沙再次悬浮,成为余流输运泥沙的来源之一。     

A Numerical Model of Nonlinear Wave Propagation in Curvilinear Coordinates

For the simulation of the nonlinear wave propagation in coastal areas with complex boundaries,a numerical model is developed in curvilinear coordinates. In the model,the Boussinesq-type equations including the dissipation terms are employed as the governing equations. In the present model,the dependent variables of the transformed equations are the free surface elevation and the utility velocity variables,instead of the usual primitive velocity variables. The introduction of utility velocity variables which...