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201.
结合某大跨双塔斜拉桥工程设计实例,采用大型有限元软件ANSYS建立了三维有限元计算模型,分析了该桥的动力特性,并采用反应谱法进行了地震反应分析。研究结果表明:由于采用了半漂浮斜拉桥体系,主梁梁端位移较大,极易造成主、引桥间碰撞且对两端伸缩缝不利,可采用弹性约束或设置阻尼器等措施来限制主梁梁端位移。 相似文献
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Dynamic response of ship-hull structure under slamming has tracked widespread attention in the marine structural design. However, our understanding on the dynamic characteristics largely relies on the symmetrical slamming cases. This paper presented a preliminary numerical investigation on the dynamic response of a truncated ship-hull structure under asymmetrical slamming based on the uncoupled CFD-FE method. Asymmetrical slamming loads were predicted through combining the seakeeping analysis and CFD method. In there, three kinds of motions (vertical, horizontal and roll motions) of 2D ship sections were obtained through the seakeeping analysis and then the slamming pressure was predicted through simulating the water entry with various motions based on CFD method. The dynamic response was analyzed through finite element method. Numerical predictions including ship motions, slamming loads and dynamic analysis were validated against published experimental data and numerical calculations. The characteristics of asymmetrical slamming loads were analyzed showing obvious asymmetry in space, and the dynamic characteristic of the ship bow structure was further clarified through discussing the deformation and stress distribution. These results are useful for readers for better understanding the dynamic characteristics of the bow structure under slamming. 相似文献
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This paper presents a simplified numerical model capable of analysing the interaction between the structural dynamic response of elastic-plastic struck plate wall of a fluid tank subjected to wedge impact and the resulting fluid motion. The Variational Finite Difference Method (VFDM) is applied to analyse the structural dynamics of the struck plate and 2-D linear potential flow theory is used to study the resulting fluid motion and its effects on the structural dynamics of the struck plate. Experiments of a wedge indenter impacting with both empty and 90% filled tanks are carried out to study the structural deformation of the struck plate. The accuracy of the developed numerical model is validated with published results and experimental results, and good agreement is achieved. Through the comparison of the impact behaviour of empty and partially filled water tank, it is found that the resulting water motion helps to reduce the structural deformation of the struck plate since part of the impact energy is dissipated by the resulting water motion. Parametric studies are performed to investigate the effect of impact velocity and water level on the structural dynamics of the struck plate of a partially filled water tank. A case study is also conducted to demonstrate the potential application of the proposed method in analysing ship-ice impact problems. 相似文献
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Bend stiffeners are subjected to cyclic loading during offshore operation or when subjected to a controlled full-scale qualification test. Due to the viscoelastic nature of the polyurethane, energy is dissipated within the material volume and the structure may experience a temperature increase, a phenomenon known as self-heating. The top connection is a flexible riser critical region in terms of fatigue, being the bend stiffener the main responsible for curvature control. As the curvature distribution is highly affected by the nonlinear time–temperature bend stiffener response, a detailed thermo-mechanical assessment may become relevant for riser lifetime and polyurethane material failure assessment, specially during accelerated full-scale tests. In the present paper (Part I), the polyurethane experimental characterization and steady-state thermo-mechanical mathematical formulation are presented for the bend stiffener self-heating assessment. A steady-state formulation is derived for a temperature dependent linear viscoelastic large deflection beam model to estimate the heat generation during harmonic tip loading. The temperature field distribution is calculated through a three-dimensional steady-state thermal model considering the viscoelastic heat calculated from the mechanical model with an iterative scheme. Stress relaxation tests are performed at different temperatures to determine the viscoelastic properties followed by thermal properties characterization through differential scanning calorimetry and by the Flash method to determine the specific heat, thermal conductivity and diffusivity, respectively. In a companion paper (Part II) the iterative numerical scheme is detailed and a case study presented. 相似文献
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自主神经功能检测对早期糖尿病自主神经功能损害的诊断价值 总被引:3,自引:0,他引:3
目的评价自主神经功能检测对早期糖尿病自主神经功能损害的诊断价值。方法50例2型糖尿病患者进行自主神经功能检查,即交感皮肤反应和心血管自主神经功能检测,并与30名健康人进行对比分析。结果糖尿病患者自主神经功能检测中交感皮肤反应,瓦氏比值和深呼吸时心率变异与对照组比较均有显著性差异(P<0.05),三者的异常率分别为70%,46%和50%;以交感皮肤反应的异常率最高,尤其以双下肢明显。立卧位血压差和冰水试验与对照组比较无显著性差异(P>0.05),其异常率分别为12%和16%。结论检测外周器官自主神经功能状态的方法中以交感皮肤反应的阳性率最高,可以作为检测早期糖尿病自主神经功能的常规筛选检查。 相似文献