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1.
深水连续刚构桥地震响应分析 总被引：2，自引：0，他引：2
本文探讨连续刚构桥在深水中地震响应的特性.首先建立了地震作用下深水桥梁的运动方程,简要阐述了该运动方程的求解方法,应用该运动方程,对一座桥墩淹没水深168m的连续刚构桥进行了地震响应分析,考察了在纵向、横向激励作用下桥墩的内力响应和位移响应特征,探讨了矩形空心截面桥墩内域水、外域水对桥墩地震响应的影响,结果表明,由于墩-水相互作用,桥墩的位移和内力响应均有明显增大,对于矩形空心墩,内域水和外域水的影响应同时计入. 相似文献
2.
考虑动水压力影响的单柱式桥墩地震反应分析 总被引：3，自引：1，他引：2
在Morison方程的基础上,用附加水质量法考虑动水压力对桥墩的影响,以单柱式桥墩为研究对象,以ABAQUS有限元软件为计算平台,建立了考虑桩-土动力相互作用的单柱式桥墩地震反应分析模型,考虑土体和桥墩混凝土的动力非线性特征,分析了地震动作用下动水压力对单柱式桥墩的墩顶相对墩底位移、加速度、剪力和弯矩反应的影响,并探讨了水位对单柱式桥墩地震反应特性的影响。结果表明:动水压力改变桥墩的地震反应特性,增大了桥墩顶部相对底部的位移、墩顶绝对加速度和墩底的内力,水位变化影响桥墩的地震反应特性。对于深水桥墩抗震设计计算,考虑动水压力效应、水位变化是有必要的。 相似文献
3.
地震易发地区的锚固岩石边坡，需要研究其地震稳定性。对于锚固典型岩石边坡，在考虑水平与竖向地震力、张裂缝积水深度、坡顶超载、锚索倾角、锚索位置、锚索拉力及静水与动水压力等的条件下，运用拟静力和拟动力方法分别推导了不同工况条件下其抗滑和抗倾覆地震安全系数。分析表明，竖向向上地震力有利于锚固岩石边坡的抗滑稳定，而竖向下的地震力有利于锚固岩石边坡的抗倾覆稳定；在相同工况条件下，当岩体放大系数等于1.0时，拟动力与拟静力方法所得锚固岩石边坡地震安全系数相差无几，但是，当岩体放大系数逐渐增大时，拟动力方法所得地震安全系数越来越明显地小于拟静力方法所得地震安全系数。因此，在抗震设计当中适当的考虑岩体放大系数，将会有利于锚固岩石边坡的安全设计。 相似文献
4.
在深水桥墩及桩基础等结构地震反应中,地震激励下的水流动水压力对水中结构的作用以及结构位形变化对水体的反作用,属于典型的流固强界面耦合问题。以一顶端伸出水面的圆柱式结构为研究对象,基于任意拉格朗日-欧拉描述的Navier-stokes方程,建立了考虑水流-结构强耦合效应的水流-结构三维有限元模型。以正弦位移波输入,考察结构材料模量、水流流速和水位、激振频率和位移幅值等多种因素,分析了结构表面作用的动水压力反应特征以及水流动力效应,探讨了水流动力效应的主要影响因素。结果表明：考虑流固强耦合作用时,结构表面作用的动水压力及其分布具有强烈的频率依赖性,高频激励可显著增强动水压力作用;由于结构周围流体具有一定的粘滞性及动载作用下具有较强的辐射阻尼效应,水流动力效应对结构的位移、内力反应均有一定的抑制作用;激振频率、水流流速和水位以及结构材料模量等因素,对水流动力效应均有一定的影响。 相似文献
5.
HUANG Yuying 《中国海洋工程》2000,14(1):1-13
—As a further development of the authors'work(Huang and Qian,1993),in this paper a newnumerical method based on the time domain boundary element technique is proposed for solving fluid-sol-id coupling problems,in which a rigid body impacts normally on the calm surface of a half-space fluid.Afundamental solution to the half-space potential flow problem is first derived with the method of images.Then,an equivalent boundary integral equation in the Laplace transform domain is established by meansof Green's second identity.Through the inverse Laplace transform and discretization in both time andboundary of the fluid region,the numerical calculation for the problem under consideration has been car-ried out.Several examples demonstrate that the present method is more efficient than existing ones,fromwhich it is also seen that the shape of the impacting body has a considerable effect on the total impactforce. 相似文献
6.
Impact forces associated with major debris flows (Jiangjia Ravine, China, August 25, 2004) were recorded in real time by a system consisting of three strain sensors installed at different flow depths. This provides the first real‐time and long‐duration record of impact forces associated with debris flows. A comprehensive approach including low‐pass filtering and moving average methods were used to preprocess the recorded signals. The upper limit of impact frequency in the debris flows was estimated at 188?66 Hz under the assumption that only coarse grains cause effective impact loadings. Thus, a low‐pass filter with a 200 Hz cut‐off frequency was needed to denoise the original data in order to extract the impact force. Then the moving average method was applied to separate long‐term and random components of the filtered data. These were interpreted as, respectively, the fluid pressure and grain impact loading. It was found that the peak grain impacts at different depths were non‐synchronous within the debris flows. The impact loadings were far greater than, and not proportional to the fluid pressures. Analysis of the impact force of 38 debris flow surges gives an empirical value for the ratio of the hydrodynamic pressure to the momentum flow density, i.e. the product of debris‐flow density and mean velocity square, which provides a very valuable basis for understanding debris flow dynamics and designing debris flow management systems. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
7.
Fixed offshore wind turbines usually have large underwater supporting structures. The fluid influences the dynamic characteristics of the structure system. The dynamic model of a 5-MW tripod offshore wind turbine considering the pile–soil system and fluid structure interaction (FSI) is established, and the structural modes in air and in water are obtained by use of ANSYS. By comparing low-order natural frequencies and mode shapes, the influence of sea water on the free vibration characteristics of offshore wind turbine is analyzed. On basis of the above work, seismic responses under excitation by El-Centro waves are calculated by the time-history analysis method. The results reveal that the dynamic responses such as the lateral displacement of the foundation and the section bending moment of the tubular piles increase substantially under the influence of the added-mass and hydrodynamic pressure of sea water. The method and conclusions presented in this paper can provide a theoretical reference for structure design and analysis of offshore wind turbines fixed in deep seawater. 相似文献
8.
The fluid-structure interaction under seismic excitation is very complicated, and thus the damage identification of the bridge in deep water is the key technique to ensure the safe service. Based on nonlinear Morison equation considering the added mass effect and the fluid-structure interaction effect, the effect of hydrodynamic pressure on the structure is analyzed. A series of underwater shaking table tests are conducted in the air and in water. The dynamic characteristics affected by hydrodynamic pressure are discussed and the distribution of hydrodynamic pressure is also analyzed. In addition, the damage of structure is distinguished through the natural frequency and the difference of modal curvature, and is then compared with the test results. The numerical simulation and test of this study indicate that the effect of hydrodynamic pressure on the structure should not be neglected. It is also found that the presence of the damage, the location of the damage and the degree of the severity can be judged through the variation of structure frequency and the difference of modal curvature. 相似文献
9.
桥梁水下桩墩结构振动台模型试验相似律验证 总被引：1，自引：0，他引：1
模拟地震振动台模型试验是研究桥梁桩墩结构抗震设计的重要方法。振动台试验结果的有效性取决于模型结构与原型结构的相似程度,不同的试验目的对应的相似关系也有差别。桥梁水下桩墩结构动力模型试验在满足结构自身相似律的同时,也要满足结构周围动水压力的相似,水体的存在限制了试验模型的相似设计。基于目前广泛应用的Buckinghamπ定理,采用量纲分析法和方程分析法,通过对比分析,在合理假设的基础上得出了桥梁混凝土桩墩结构振动台破坏试验模型设计的实用相似关系。最后,以某实际水下桥梁桩墩结构为例,通过计算分析验证了相似关系公式并对产生的误差进行了判断。结果表明:原型结构与模型结构的地震动力响应满足预计的相似关系;推导的相似律能在一定程度上避免模型设计的困难,较适用于实际应用。 相似文献
10.
大足井位于重庆市大足县拾万镇,井深108.7m,观测含水层为J2S泥岩夹砂层的风化裂隙潜水层。多年的观测结果表明,每当相距仅14.6m的邻井抽水时,该井水位不仅不降,反而上升,是国内外罕见的奇异现象。通过对这一现象进行的观测资料分析、井区地质-水文地质条件调查、现场试验观测及理论分析等得出,大足井水位对邻井抽水的奇异响应是在特定的水文地质条件下,抽水降落漏斗外边界带上因水流速度较大引起的动水压力使该处的观测井产生的特殊井水位动态。 相似文献