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The consistent transmitting boundary condition is a powerful numerical technique for frequency domain analysis of wave problems in unbounded elastic media. A second-order complex-valued eigen-problem is associated with this method and the computed eigenmodes are used to formulate the nodal forces acting on the lateral boundaries of a Cartesian computational domain. Usually, all eigenmodes are computed and used in the consistent transmitting boundary conditions to simulate the infinite extent of the elastic medium. In this paper, it is demonstrated that by selecting a reduced number of relevant eigenmodes it is possible to produce similar results and consequently reduce the overall computational cost. This is highly desirable for soil–structure interaction problems involving wide ranges of frequencies and large-size domains with many sub-layers. The efficiency of the proposed approach is investigated by considering, first, the case of foundation vibration over rigid bedrock and, second, the effectiveness of a wave barrier to reduce the transmitted vibrations caused by a surface harmonic loading. 相似文献
33.
波浪作用下方箱-水平板浮式防波堤时域水动力分析 总被引:1,自引:0,他引:1
在线性化势流理论范围内求解方箱-水平板浮式防波堤的波浪绕射和辐射问题,从时域角度分析了浮式防波堤的水动力特性.采用格林函数法将速度势定解问题的控制微分方程变换成边界上的积分方程进行数值求解,浮式防波堤的运动方程采用四阶Runge-Kutta方法求解.对不同层数水平板的浮式防波堤的波浪透射系数、运动响应和锚链受力进行了计算分析,结果表明方箱相对宽度对方箱-水平板浮式防波堤的波浪透射作用有重要的影响,透射系数随着方箱相对宽度的增加而减小.对于方箱加二层水平板的浮式防波堤,在本研究的计算条件下,当方箱相对宽度从0.110增加至0.295时,透射系数从0.88减小至0.30.水平板有利于增加浮式防波堤对波浪的衰减作用,但随着水平板层数从0增加至2,这种波浪衰减作用增加的程度趋弱.方箱-水平板的浮式防波堤的运动量小于单一方箱防波堤的运动量.与此对应,方箱-水平板防波堤的锚链受力小于单一方箱防波堤的锚链受力. 相似文献
34.
In this paper, a finite element model of a soil island is coupled to both a consistent transmitting boundary and a paraxial boundary, which are then used to model the propagation of waves in semi-infinite elastic layered media. The formulation is carried out in the frequency domain while assuming plane strain conditions. It is known that a discrete model of this type, while providing excellent results for a wide range of physical parameters in the context of a half-space problem, may deteriorate rapidly at low frequencies of excitation. This is so because at low frequencies the various waves in the model eventually attain characteristic wavelengths which exceed the distance of the bottom boundary, which then causes that boundary to fail. Also, the paraxial boundaries themselves break down at very low frequencies. In this paper, this difficulty is overcome and the model׳s performance is improved upon dramatically by incorporating an artificial buffer layer sandwiched between the bottom of the soil medium and the underlying elastic half-space. Applications dealing with rigid foundations resting on homogenous or layered half-space media are shown to exhibit significant improvement. Following extensive simulations, clear guidelines are provided on the performance of the coupled model and an interpretation is given on the engineering significance of the findings. Finally, clear recommendations are provided for the practical use of the proposed modelling strategy. 相似文献
35.
本文选用不同的方法对两个导线线圈进行了射线检测,主要采用透射式工业CT检测和康普顿背散射成像检测两种射线层析检测方法,有效检测了导线线圈内部的缺陷情况,并指出射线层析检测作为一项新技术和新手段,可充分应用在航天产品的无损检测中。 相似文献
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Masayoshi Nakashima 《地震工程与工程振动(英文版)》2012,11(1):11-21
Steel fiber reinforced cementitous composites(SFRCC)is a promising material with high strength in both compression and tension compared with normal concrete.The ductility is also greatly improved because of 6%volume portion of straight steel fibers.A steel beam-column connection with Steel fiber reinforced cementitous composites(SFRCC) slab diaphragms is proposed to overcome the damage caused by the weld.The push-out test results suggested that the application of SFRCC promises larger shear forces transferred through headed studs allocated in a small area in the slab. Finite element models were developed to simulate the behavior of headed studs.The failure mechanism of the grouped arrangement is further discussed based on a series of parametric analysis.In the proposed connection,the SFRCC slab is designed as an exterior diaphragm to transfer the beam flange load to the column face.The headed studs are densely arranged on the beam flange to connect the SFRCC slab diaphragms and steel beams.The seismic performance and failure mechanism of the SFRCC slab diaphragm beam-column connection were investigated based on the cyclic loading test.Beam hinge mechanism was achieved at the end of the SFRCC slab diaphragm by using sufficient studs and appropriate rebars in the SFRCC slab. 相似文献
38.
本文在全部入射角范围内系统地讨论了时域局部透射边界真实的反射系数及其与理想稳态和理想暂态反射系数的关系。文中指出,后两者可分别用作前者上,下限的估计;同时,就时域逐步积分计算而言理想暂态较之理想稳态更接近真实情形,简便的理想暂态反射系数可用于在全部入射角范围内度量边界是的误差。 相似文献
39.
FiniteelementsimulationofsteadystateSHwavemotionZhen-PengLIAO(廖振鹏)andGuangYANG(杨光)(InstituteofEngineeringMechanics,StateSeism... 相似文献
40.
本文以饱水两相介质的土力学模型为研究对象,在假定两相介质为弹性介质条件下,采用了显式有限元法和透射边界进行了饱和弹性半空间动力响应问题的研究。为避免谐波输入初始间断的影响,文中提出了一个处理函数,并以弹性半空间为算例,对饱水介质和单相介质分别进行了在底边界P波垂直入射时的动力响应分析,验证了该处理函数的有效性和实用性。 相似文献