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81.
The dynamic characteristics of a tunnel structure used to protect underwater power cables, the so-called A-duct, were determined for anchor collisions to provide a procedure for damage assessment and recommendations. The required physical quantities of five target anchors, including the drag coefficient, were obtained using an element-based finite-volume method and ANSYS-CFX software. The terminal velocities of the anchors were then calculated to maximize the colliding kinetic energy. For collision analysis, four parameters (anchor type, ground condition, collision velocity, and collision point) were considered, and the A-duct was modeled based on the Riedel–Hiermaier–Thoma concrete model using ANSYS-Autodyn software. Our analysis results indicated severe damage (D = 1) for most of the gauge points; the damaged area and level increased with the anchor weight. The results showed that the damage was concentrated in the collision area for stock anchors; however, for stockless anchors, damage was also evident in adjacent areas (i.e., damage propagation) due to the anchor head shape as well as the transfer mechanism provided by its reinforcing nets. Accordingly, the 2-ton stock anchor caused more damage at the gauge points near the collision location than the 2-ton stockless anchor. Second, regardless of the ground conditions and rotation angle of the anchor heads with respect to the vertical axis, the damage levels were almost identical. Fixed boundary conditions and non-rotational angle were sufficient for the model used. Third, the damaged areas became smaller when the anchor collision locations deviated from the reference gauge point (P1), i.e., the center of the A-duct. Finally, a comparison of the field-test results to equivalent numerical collision simulations indicated that the size of the predicted and experimentally observed damaged areas were in agreement within 7%. 相似文献
82.
83.
This paper presents an estimation and analysis of ship exhaust emissions and their externalities in the popular cruise destinations of Dubrovnik (Croatia) and Kotor (Montenegro) along the eastern coast of the Adriatic Sea. To this extent, the recent record (2012–2014) of cruise ships calling at these ports is used to model and estimate the ship exhaust emission inventories and externalities within the associated bays and ports.The results indicate that cruise ship traffic produces continuously increasing air pollution in both ports over recent years. More importantly, however, the analysis of the ship operating characteristics reveals that for any given ship traffic involving specific vessels using marine fuel of a given quality, the presence of other factors (e.g. berth availability, berth accessibility etc) can also influence the ship emission levels. This is particularly evident in the case of the port of Kotor where berth space insufficiency dictates the need for ship anchorage thus leading to increased air pollution and costs of associated damage.The application and results of the aforementioned ship activity-based methodology to the ports of Dubrovnik and Kotor improves our understanding of ship emissions in cruise bays and ports, and contributes toward the implementation of port policies for the effective control of air quality in such environmentally sensitive locations. 相似文献
84.
大型桥梁健康监测研究进展 总被引:43,自引:2,他引:41
回顾桥梁健康监测的发展历程。介绍桥梁健康监测系统的组成、监测内容功能及特点。对信号分析与处理的传统谱分析方法与小波变换、希尔波特黄变换(Hilbert Huang)进行比较。介绍最新的信号时频分析方法希尔波特黄变换的具体算法,及其在结构参数识别、损伤识别、消除实测南京长江大桥应变信号中的对讲机干扰等方面的具体应用。对动力指纹分析法、模型修正与系统识别法、神经网络法、遗传算法5种损伤检测方法的基本原理、特点及发展动态进行概述和总结,指出神经网络技术结合遗传算法是结构损伤检测的发展方向之一。 相似文献
85.
86.
对铁路信号系统上道信号设备雷电电磁脉冲抗扰度进行室内动态模拟试验,是保障信号设备应用可靠性的重要环节。按照现行铁道行业标准规定的试验方法和试验检测方法进行室内动态模拟试验,存在着对防护盲区和冲击损坏积累效应漏检的问题。通过分析试验结果,说明防护盲区、冲击损坏积累效应产生的原因和漏检的可能性,并提出相应防范措施。 相似文献
87.
This paper presents an application of shallow water theory to describe the motion of floodwater inside a rolling ship in damage
condition. The time domain theoretical approach to the coupled problems of ship and water inside compartment motions is briefly
described, including the method used to solve for the water motion characteristics and forces exerted on the ship. This approach
is applied to the study of the behaviour of a passenger Ro–Ro ship in regular beam seas and numerical results are given for
the intact and damaged conditions. Comparison is made with experimental results. For the damaged condition, the characteristics
of the floodwater motion are studied in the time domain for a number of different wave frequencies. The shape of the free-surface
and phase of water motion in relation to the ship roll motion are shown for several wave frequencies. The dynamic floodwater
roll moment is also shown and compared with the static roll moment (flat horizontal free surface), allowing the conclusion
that the dynamic roll moment is much larger than the static roll moment, for high wave frequencies, and is in phase opposition
in relation to the roll motion. 相似文献
88.
针对原有旧白色路面破损原因的分析,介绍路面施工处理措施的方法,提出沥青混凝土路面施工中质量控制措施及建议. 相似文献
89.
In this investigation, ductile fracture in stiffened and unstiffened panels is simulated employing the fracture criterion, which depends on the mesh size, stress state and damage induced softening. The aim of the study is to show that employed fracture criterion removes mesh size effects more efficiently than traditional fracture criteria adjusted only on the basis of uniaxial tension. Fracture model is implemented into Finite Element software ABAQUS using user-defined material, VUMAT-subroutine, available for shell elements. Mesh size sensitivity analysis is carried out. Finite element simulation results are validated with experimental measurements available in literature. Comparison of numerical and experimental results shows that simulations effectively capture most of the experimentally observed features, especially when considering different mesh densities. In most cases, mesh size effects are considerably reduced compared with the fracture criteria adjusted on the basis of a uniaxial tension. 相似文献
90.