CFRP composite retrofitting effect on the dynamic characteristics of arch dams

The purpose of this study is to investigate the effect of retrofitting dynamic characteristics of a damaged laboratory arch dam model, subsequently repaired with high-strength structural mortar and strengthened with composite carbon fiber reinforced polymer. This study constructed in laboratory conditions is a prototype arch dam–reservoir–foundation model. Five test cases of ambient vibration on the arch dam model illustrate the changes in dynamic characteristics: natural frequency, mode shape, and damping ratio, before and after retrofitting. The ambient vibration tests collected data from the dam body during vibrations by natural excitations which provided small impacts and response signals from sensitivity accelerometers placed at crest points. Enhanced Frequency Domain Decomposition Method in the frequency domain extracts the experimental dynamic characteristics. At the end of the study, experimentally identified dynamic characteristics obtained from all test cases have been compared with each other. Apparently, after the retrofitting, the natural frequencies of the dam body increased considerably, demonstrating that the retrofitting, including repairing and strengthening is very effective on the flashback of initial dynamic characteristics.     

Multibody dynamical modeling of the FPSO soft yoke mooring system and prototype validation

The Soft Yoke Mooring System (SYMS) is a single point mooring system for shallow water. It is composed of a mooring framework, mooring legs, yoke, and single point, and is located at the Floating Production Storage and Offloading (FPSO) through 13 hinge joints, such as universal joints and thrust bearings. Mooring restoring force, motions and postures of mooring components, and mechanical behaviors of hinge joints are major criteria for the structural design of the SYMS. Aiming at the difficulties of the multibody dynamics in traditional design of the SYMS, a multi-body dynamic mathematical modeling with seven independent degrees of freedom (DOFs) which is applicable to prototype field engineering was developed in this study. The proposed mathematical modeling of the SYMS multibody dynamic system has several advantages: 1. Internal tribological behaviors in hinge joints are considered within the presented multibody dynamics model to illustrate the good dynamic effects of the SYMS. 2. The multibody dynamic model can be applied in field service. Correctness and feasibility of the proposed multibody dynamic simulation method for describing motions and postures of hinges and single-body were validated by the prototype monitoring data. 3. The horizontal restoring force of the SYMS was calculated according to field measurement data. The motion state of each single body and internal stress distributions at each hinge joint in the SYMS are given. 4. The multibody dynamics calculation program can be directly used for the real-time monitoring of mechanical behaviors of the SYMS under the service state. The simulated results can provide real-time guarantee for safety alarming of the system. The vulnerability of the mooring system in service was evaluated based on long-term monitoring data analysis.     

经验正交函数分解在地壳垂直形变场分析中的应用

论述了应用经验正交函数分解方法分析地壳垂直形变场,处理分析了甘肃河西地区的实测资料,结果显示,地壳垂直形变场的第一典型场对中强以上地震发震地点的判定有重要意义;而地壳垂直形变场的时间权系数能够表示区域地壳运动的相对强弱,它可以作为区域地震危险性判定的时间判据。     

Dynamic simulation of hydrokinetic hammer based on virtual prototyping technology

This study presented the specified steps of comprehensively analyzing the hydraulic-driven hammer system with the application of the Virtual Prototype Technology. By comparing the simulation results with experimental phenomena and data, the correctness of simulation analysis conclusion is verified. Meanwhile, by means of its perfect visualization, the internal work process which can not be seen before is simulated. The mechanism of some abnormal phenomena encountered during the experiment is explained.     

Numerical Study of the Oil Spill Trajectory in Bohai Sea,China

Sixteen numerical experiments are conducted using the General NOAA Operational Modeling Environment (GNOME) to numerically study the oil spill trajectory in the Bohai Sea, China, for the purpose of providing information for the oil cleanup and disaster mitigation. High resolution coastline and topography data investigated by China's 908 Program are used to accurately describe the regional geographic feature of the Bohai Sea. Currents and waves required by GNOME are generated by the Hybrid Coordinate Ocean Model and Simulating Wave Nearshore, respectively. Experimental results show that oil spilled in different seasons and at different locations will result in completely different spilling trajectories, traveling distances, and polluting areas. Knowing that information comprehensively is vital to pollution control. Another important goal of this work is to provide users with simulated oil spill trajectory information through China Digital Ocean Prototype System (CDOPS), a grand marine information platform for managing, displaying, and public sharing of the data investigated by the China 908 Program. Users can obtain the trajectory, spreading, and potential impact area of the spilled oil through the oil spill module in CDOPS.     

哈密坳陷二叠纪-三叠纪原型盆地恢复及沉积中心演化特征

 本文主要根据野外露头资料、地震资料及钻井资料,运用平衡剖面法、地震地层法、地层对比法、邻近厚度比值法及沉积速率比值法计算哈密坳陷二叠系-三叠系地层剥蚀厚度,在残余地层厚度的基础上,恢复哈密坳陷二叠系-三叠系原始地层厚度,进而对哈密坳陷二叠纪-三叠纪原型盆地进行恢复,探讨其沉积中心的演化过程。     

Hull component interaction and scaling for TLP hydrodynamic coefficients

The purpose of this paper is to validate a new method that can be used by offshore platform designers to estimate the added mass and hydrodynamic damping coefficients of potential Tension Leg Platform hull configurations. These coefficients are critical to the determination of the platform response particularly to high frequency motions in heave caused by sum-frequency wave forcing i.e. “springing”. Previous research has developed the means by which offshore platform designers can extrapolate anticipated full-scale hydrodynamic coefficients based on the response of individual model scale component shapes. The work presented here further evaluates the component scaling laws for a single vertical cylinder and quantifies the effects due to hydrodynamic interaction. Hydrodynamic interaction effects are established through a direct comparison between the superposition of individual hull component coefficients and those evaluated directly from complete hull configuration models. The basis of this comparison is established by the experimental evaluation of the hydrodynamic coefficients for individual hull components as well as partial and complete platform models. The results indicate that hydrodynamic interaction effects between components are small in heave, and validate component scaling and superposition as an effective means for added mass and damping coefficient estimation of prototype platforms. It is found that the dependency of damping ratio with KC for a TLP is almost identical to that of a single column, thus offering a scaling methodology for prototype damping ratio values.     

Components of suction caisson capacity measured in axial pullout tests

Suction caissons are the foundation of choice for offshore structures in deep water. Systematic study of caisson behavior is relegated to the laboratory due to the high cost of full-scale testing. Our laboratory caisson was installed in normally consolidated clay using dead weight and suction. Tensile axial capacity was measured with the top cap vented or sealed, and with the soil undrained or drained. For the common case of rapid pullout with a sealed top, the test results indicate an external side resistance factor (α) of 0.5–0.8 and a reverse end bearing factor (N_c) of 13–21.     

四川盆地及邻区二叠纪梁山-栖霞组沉积盆地原型及其演化

中二叠世的上扬子地区开始经历大规模的海侵作用,形成了较为稳定的碳酸盐岩沉积建造。探究该时期四川盆地及邻区沉积充填规律与构造演化特征,是揭示原型盆地成因机制的关键,又是认识四川盆地多旋回叠加过程的重要一环。在前人研究成果的基础之上,综合利用钻井、野外剖面等地质资料,重建了梁山组、栖霞组沉积时期原型盆地构造-古地理格局,并分析其构造-沉积演化过程。主要受继承自晚石炭世以来的中部隆升,东西两侧下沉的的古地貌和初期大规模海侵作用的影响,中二叠世梁山组沉积时期,本地区以滨岸-潮坪沉积体系为特征;栖霞组沉积早期,逐渐过渡到碳酸盐岩台地沉积环境,受区域性伸展作用的影响,海平面相对上升,以开阔台地沉积环境为特征;栖霞组沉积晚期,海平面相对下降,以局限台地和台缘滩沉积环境为特征。因此,反映出四川盆地及邻区在该时期主要受伸展裂解作用的影响,可被认为是一个典型的克拉通内坳陷和边缘裂陷盆地。海平面升降的旋回性变化和盆地的差异性沉降对该时期原型盆地的沉积充填样式和古地理格局的演变产生了重要影响。     

Effects of new variables on the overtopping discharge at steep rubble mound breakwaters — The Zeebrugge case

This paper describes on the one hand parametric tests on wave overtopping for a steep rubble mound breakwater in Zeebrugge, Belgium. On the other hand the comparison between prototype measurements at the breakwater and their scale reproductions in two laboratories is dealt with. The objective is to gain information on possible scale and model effects for wave overtopping from this comparison. The prototype measurements are described together with the resulting dataset of 11 storms where wave overtopping occurred. Scale models and the laboratory measurements are described into detail mentioning similarities and differences to the prototype. Several model effects are identified and special attention is given to wind effects and to the placement pattern of the armour units, respectively. Monte Carlo simulations have been performed to get an idea about the influence of selected model uncertainties. Finally, scale effects are discussed and the influence of model and scale effects for the performed tests is quantified. Recommendations on how to treat these effects are presented.