Wave-Current Forces on Slender Circular Cylinders

- A series model tests of wave forces by both regular and irregular waves combined with currents on single piles and bipiles in tandem and parallel arrays have been carried out. Based on Morison Equation, linear wave theory and linear wave spectrum theory as well, the characteristics of inline, lift and resultant forces on cylinders have been analyzed respectively. The drag, inertia and lift coefficients CD, CM and CL f皉 single piles related to KC number and the grouping effect coefficients of inline, lift and resultant forces on bipiles in tandem and parallel arrays related to KC number are given in this paper.     

Efficient Focusing Models for Generation of Freak Waves

Four focusing models for generation of freak waves are presented. An extreme wave focusing model is presented on the basis of the enhanced High-Order Spectral (HOS) method and the importance of the nonlinear wave-wave interaction is evaluated by comparison of the calculated results with experimental and theoretical data. Based on the modification of the Longuet-Higgins model, four wave models for generation of freak waves (a. extreme wave model + random wave model; b. extreme wave model + regular wave model...     

近场强地震动模拟中对破裂的方向性效应和上盘效应的表达.

为了模拟近场强地震动，采用了基于有限断层模型的一种随机合成方法．震源破裂面被剖分成一定数量的子源，总的地震矩分成数量更多的子震的矩．一给定子源中一次子震引起的场地地震动的傅氏谱，通过考虑点源的谱、随着距离的衰减、能量耗散及近地表效应等导出．据此幅值谱和一个随机相位谱，并与一个时程包络函数结合，合成一个子震时程．将各子源中各个子震引起的所有时程叠加，得出场地的地震动时程．叠加中，各子震时程之间的时滞，据子震发震时差和子源至场地的距离差别引起的时差确定．对一个设定地震，选用4个断层面倾角，计算了近场21个地点的地震动．结果表明，本文方法可以很好地表达破裂的方向性效应和上盘效应．为了验证方法的可靠性，对1994年美国北岭地震中3个近断层台站MCN，LV3和PCD模拟的地震动与实际记录的加速度反应谱和时程作了比较．      

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.     

Vertical 2D Modeling of Free Surface Flow with Hydrodynamic Pressure Using SIMPLE Arithmetic in σ Coordinates

A numerical model for shallow water flow has been developed based on the unsteady Reynolds-averaged Navier-Stokes equations with the hydrodynamic pressure instead of hydrostatic pressure assumption. The equations arc transformed into the a-coordinate system and the eddy viscosity is calculated with the standard k -ε turbulence model. The control volume method is used to discrete the equations, and the boundary conditions at the bed for shallow water models only include vertical diffusion terms expressed with wall functions. And the semi-implicit methed for pressure linked equation arithmetic is adopted to solve the equations. The model is applied to the 2D vertical plane flow of a current over two steep-sided trenches for which experiment data are available for comparison and good agreement is obtained. And the model is used to predicting the flow in a channel with a steep-sided submerged breakwater at the bottom, and the streamline is drawn.     

碟形网箱水动力特性的研究

根据物模实验得到碟形网箱在不同海况条件下的受力并给出了其估算方法和公式及其相关系数的取值,同时总结了碟形网箱的运动特性。     

An Efficient Model for Transient Surface Waves in Both Finite and Infinite Water Depths

A numerical model is developed to simulate fully nonlinear extreme waves in finite and infinite water-depth wave tanks. A semi-mixed Eulerian-Lagrangian formulation is adopted and a higher-order boundary element method in conjunction with an image Green function is used for the fluid domain. The boundary values on the free surface are updated at each time step by a fourth-order Runga-Kutta time-marching scheme at each time step. Input wave characteristics are specified at the upstream boundary by an appropr...     

Experimental Investigation on Durability of Reinforced Concrete Beams in A Simulated Marine Environment

1. IntroductionConcrete is widely used for nearshore and offshore marine structures and bridges (Song et al.,2000; Wang and Song, 2004). Experience has shown that the durability of marine concrete structuresis generally good; however, some cases of serious deterioration also exist due to the lack of durability(Metha and Gerwick, 1982). Under marine conditions, concrete, especially concrete in the splashand tidal zone, is attacked, resulting in corrosion of reinforcing bars. Corrosion of rein…     

辽宁西部九佛堂组昼蜓化石的新发现及其地质意义

发现于辽宁省义县早白垩世九佛堂组上段地层中的昼蜓化石(孟氏丽昼蜓Abrohemeroscopus mengi Ren，Liu et Chen，2003)与北京西山卢尚坟组的巴依萨昼蜓(Hemeroscopus baissicus Pritykina，1977)在形态上比较相似，但在演化程度上更为原始，主要体现在后翅臀套较小(仅有6～7个翅室)，径增脉(Rspl)缺，后翅CuAa脉弯曲、带有5个明显的后分支，前翅MP脉短、终止于翅后缘近翅结处，翅痣下有一个明显的支脉，后翅CuAa和MP域基部较窄、在三角室下方仅有1排翅室。据此，九佛堂组上段的地质时代定为早白垩世早期(Berriasian-Hauterivian)较为合理。     

New Material of Sinosauropteryx (Theropoda:Compsognathidae) from Western Liaoning,China

An incomplete specimen of Sinosauropteryx prima collected from the Early Cretaceous Yixian Formation of the Dawangzhangzi area in Lingyuan, western Liaoning is depicted. It represents the first systematically described material of this feathered compsognathid outside the Sihetun area in Beipiao. This specimen shows some diagnostic features of Sinosauropteryx prima, such as the very short forelimb in relation to hindlimb with the length ratio of humerus plus radius to femur plus tibia just around 30%, and the long and massive first manual ungual subequal in length to radius. The presence of Sinosauropteryx prima only at Sihetun and Dawangzhangzi supports the suggestion that the fossil-bearing beds in the Sihetun and Dawangzhangzi areas are equivalent to each other within the Yixian Formation.