井水位的振荡与地震波

利用弹性理论和渗流理论研究了井水位振荡试验,给出了一种计算水井含水层频率特性参数（固有振动周期和阻尼系数）的新方法,对５口水井进行了ＳＬＵＧ试验,计算水井含水层的固有振动周期和阻尼系数,分析了水井对地震波响应的规律和内在联系。水井含水层系统对地震波的响应主要取决于水井含水层系统的固有振动周期和振动的阻尼系数,固有振动周期越是接近地震波－瑞利波的振动周期２０ｓ振动的阻尼系数越小,它对地震波的响应越好     

井水位振荡试验及其结果

通过鲁04井的频率特性试验,求出了该井含水层系统的频率特性参数,固有振动周期为40.59s,阻尼系数为0.0362s-1。并且计算出鲁04井含水层的导水系数为1.8×10-3m2/s。利用这些结果解释了鲁04井对地震波响应比珍珠泉井差的原因     

水井含水层导水系数及其对地震波的响应

利用弹性理论和渗流理论研究了井水位振荡试验,给出了一种计算水井含水层渗流特性参数的新方法。该方法不是用井水位的恢复曲线,而是用井水位的振荡曲线计算出水井含水层的导水系数。对５ 口水井的导水系数及其对地震波的响应进行了统计,结果表明：水井含水层的导水系数越大,井水位对地震波响应的幅度越大,响应的次数越多。     

Free vibration of soils during large earthquakes

Free vibration of soils happens frequently during some large earthquakes, perhaps seeming like a paradox. This happens because the energy released from seismic sources in some cases is not stationary in time, allowing relaxation intervals in between without important seismic wave arrivals in which free soil vibration happens. Two techniques to estimate the natural period of the free vibration from accelerograms are presented: autocorrelograms and Fourier spectra. Both techniques sometimes allow measuring higher mode frequencies of the soil for the three first modes as well as modal damping. Free vibration modal periods satisfy the classic 1D equation S-wave theory. The presence of free vibrations corresponds to shear wave soil energy radiation episodes rather than to energy amplification of incoming stationary seismic shear waves suggested by the dynamic soil amplification. These results explain the discrepancies observed between the theoretical soil dynamic amplification and the accelerographic measurement. Observation of free vibration of soils is not always possible, it depends on the duration of the time windows without important seismic waves arrivals compared to the natural period and damping of the soil.     

济南珍珠泉井水固有振荡试验的解释

本文介绍了济南珍珠泉井水固有振荡试验结果.利用振动理论和Cooper水井-含水层模式对试验进行了解释.计算出珍珠泉水井-含水层系统的阻尼系数和固有振动的角频率.该系统阻尼系数小,角频率恰好和瑞利波角频率相近,因此珍珠泉井水位对地震瑞利波响应的振幅特别大.井水固有振荡试验是一种简便易行、经济迅速的方法,它比其它现场试验方法更宜于推广应用.     

阻尼连体结构地震响应影响参数研究

针对阻尼连体结构,采用串并联质点系层模型,沿连体设置方向施加El Centro1940地震波,讨论了毗邻结构自振周期比与连接体阻尼刚度变化对阻尼连体结构地震响应的影响。研究结果表明:毗邻结构自振周期比与连体阻尼刚度对结构的地震响应影响较大,存在一个使结构地震响应为最优的周期比与阻尼刚度值,为实际工程应用和研究提供一些参考。     

平台地形对地震地面运动特征周期值的影响

本文人工合成了36条代表不同频谱特性的地震动,构造了简单的平台地形,并利用人工合成地震动作为平台地形计算输入地震波,获得了地表观测点的时程和反应谱.在此基础上,分析了具有不同高度、侧向坡降和介质阻尼等的平台地形对地震动特征周期值的影响.研究的结果表明:当平台高度与入射地震波优势波长相比较小时,平台的高度、侧向坡降、阻尼比等对地震动特征周期值的影响不大,此时单个平台地形地表地震动的特征周期主要依赖于入射地震动的特征周期,而且一般比入射地震动的特征周期略有增大;当平台高度与入射地震波优势波长相比较大时,平台高度对地表地震动特征周期影响较大.     

岩土介质随机性对沉积河谷地震动放大效应的影响

基于间接边界元法计算沉积河谷对平面P波和SV波的二维散射，着重考察沉积介质波速比和材料阻尼比的随机性对河谷地震动放大效应的影响.利用蒙特卡罗方法随机模拟产生了波速比样本和阻尼样本各30组，给出了不同入射角度和频率的P波和SV波入射下河谷随机响应的单频和频谱结果.算例分析结果表明:①地表位移响应幅值的变异系数极值均显著大于波速比变异系数，且波速比的随机性对地表位移的影响在体系共振频率处最为显著，地表位移的标准差最大可达7.168；低频情况下，沉积中部地震动反应的变异性更显著，高频情况下则在沉积河谷边缘变异性最大；②入射角对地表位移响应变异系数极值的影响不大，但对变异系数空间变化的影响显著；③阻尼比随机性对地表位移的影响在低频情况下较小，在高频情况下则较明显，尤其是在沉积河谷的体系自振频率处，其影响最为显著.      

The effect of travelling seismic waves on the dynamic response of earth dams

A theoretical investigation of the dynamic response of earth dams to the travelling seismic waves is presented. The earth dam is simplified as a truncated two-dimensional elastic wedge. The dam body consists of an isotropical linear viscoelastic material with homogeneous elastic modulus and density. The seismic waves travel along the longitudinal direction of the earth dam. The numerical calculations show the following. (i) For the longitudinal mode of vibration, the greater the ratio (H/L) of the height to the lenght of the complete wedge, the more the natural transverse period of vibrational of the two-dimensional wedge is less than that of the one-dimensional wedge. Especially for the first two natural transverse period, this influence is large. The decrease of the ratio of the natural transverse period for a two-dimensional wedge to that for a one-dimensional wedge with the ratio H/L is rapid for the higher than for the lower longitudinal modes. (ii) Comparing with the one-dimensional wedge, the natural transverse periods for the two-dimensional case in the complete wedge are lower, and they will increase as the coefficient of truncation, h/H increases. (iii) When the frequency of forced vibration is less than the natural transverse frequency for one-dimensional wedge, the amplification is less for a two-dimensional wedge than for a one-dimensional wedge. (iv) When the phase difference of ground motion at both ends of the dam equals π, the amplification for a two-dimensional wedge is less than that for a one-dimensional wedge, but when the phase difference equals nπ, (n > 1), the situation is reversed. (v) As the coefficient of truncation, h/H, increases, the displacement model partecipations decrease monotically. (vi) In general, the displacement caused by an earthquake is greater for a one-dimensional wedge than for a two-dimensional wedge when considering the seismic waves travelling, but the acceleration response of a two-dimensional wedge with long length of dam to travelling seismic waves with long dominant period is greater than that of a one-dimensional wedge. When the length of the dam is short enough, the response of a two-dimensional wedge without considering the influence of travelling seismic waves always gives the greatest value.     

Characteristics and method of synthesis seismic wave based on wavelet reconstruction

A novel method of synthesizing seismic wave using wavelet reconstruction is proposed and compared with the traditional method of using theory of Fourier transform. By adjusting the frequency band energy and taking it as criterion, the formula of synthesizing seismic wave is deduced. Using the design parameters specified in Chinese Seismic Design Code for buildings, seismic waves are synthesized. Moreover, the method of selecting wavelet bases in synthesizing seismic wave and the influence of the damping ratio on synthesizing results are analyzed. The results show that the synthesis seismic waves using wavelet bases can represent the characteristics of the seismic wave as well as the ground characteristic period, and have good time-frequency non-stationary.     

利用小波重构合成地震波方法及特性研究

针对傅里叶变换合成地震波理论的不足，提出一种利用小波重构合成地震波的方法. 以控制频带能量为标准，推导了合成地震波的公式. 运用抗震设计规范中的相关设计参数合成了地震波，并分析研究了在合成地震波时小波函数基的选取方法和阻尼比对合成结果的影响. 结果表明，用小波重构合成的地震波能够反应地震波基本特性和场地特征周期，并具有很好的时频非平稳性.      

抗震结构的阻尼减振效果分析

研究了抗震结构的阻尼减振效果。首先，考虑了单自由度体系在不同频率简谐干扰作用下阻尼比对结构反应的减小效果；然后，考虑了阻尼比对结构地震反应谱的影响，分析了我国现行建筑抗震设计规范反应谱，并讨论了不同阻尼比对水平地震影响系数的修正公式。     

双座串联大跨度斜拉桥粘滞阻尼器参数分析

以双座串联大跨度斜拉桥-珠海洪鹤大桥为背景，根据桥梁自振特性及场地效应，生成了三组人工波，采用纵向+2/3竖向的地震作用组合输入方式，通过非线性时程分析，系统的研究了粘滞阻尼器对双座串联大跨度斜拉桥减震性能的影响。同时为了确定粘滞阻尼器的最优参数，对粘滞阻尼器的阻尼系数C和速度指数α进行了参数敏感性分析。结果表明:设置纵向粘滞阻尼器能够显著减小双座串联斜拉桥的纵向位移响应，减小主梁在串联处发生碰撞的概率，同时改善主塔塔底结构受力情况，具有良好的耗能减震效果。综合考虑安全性、适用性和经济性等方面，最后给出针对洪鹤大桥的最优粘滞阻尼器参数:速度指数α为0.3，阻尼系数C为3 000kN/（m/s）^0.3。     

台湾某钢框架大楼采用阻尼器补强结构减震效果评析

阻尼器是一种效果良好的减震装置,将阻尼器安装于结构中能够适时为结构体系提供阻尼力,从而减小地震作用对结构的破坏。黏滞阻尼器对振动的反应比较敏感,在结构受到较小振动时就可以发挥其减震效果,其阻尼力会随着振动周期和使用状态温度的不同而变化。当地震发生时,安装在结构中的阻尼器会消减地震作用,降低传导到主结构体系的地震能量,减小结构相对位移。本文介绍了黏滞阻尼器的工作原理和安装有黏滞阻尼器的结构体系的阻尼比的计算方法,对减震结构的减震效果的评析方法做出探讨,并以一安装有黏滞阻尼器的台湾某既有钢框架结构为例,分析了(1)该结构在遭受地震作用时的地震反应;(2)该结构体系在不同地震作用水平时的阻尼比,包括主体结构阻尼比和黏滞阻尼器阻尼比;(3)结构安装黏滞阻尼器后的减震效果。实例对本文的减震评析方法和减震效果进行了说明和分析,计算及分析结果表明利用黏滞阻尼器加固既有结构能够取得较好的减震效果,本文所提减震效果评析方法是一种实用有效的评析方法,对类似工程的减震评析具有一定的参考价值。     

New approach to analyzing soil-building systems

A new method of analyzing seismic response of soil-building systems is introduced. The method is based on the discrete-time formulation of wave propagation in layered media for vertically propagating plane shear waves. Buildings are modeled as an extension of the layered soil media by assuming that each story in the building is another layer. The seismic response is expressed in terms of wave travel times between the layers, and the wave reflection and transmission coefficients at layer interfaces. The calculation of the response is reduced to a pair of simple finite-difference equations for each layer, which are solved recursively starting from the bedrock. Compared with commonly used vibration formulation, the wave propagation formulation provides several advantages, including the ability to incorporate soil layers, simplicity of the calculations, improved accuracy in modeling the mass and damping, and better tools for system identification and damage detection.     

Shaking table test and numerical simulation of an isolated cylindrical latticed shell under multiple-support excitations

In order to study the influence of the ground motion spatial effect on the seismic response of large span spatial structures with isolation bearings, a single-layer cylindrical latticed shell scale model with a similarity ratio of 1/10 was constructed. An earthquake simulation shaking table test on the response under multiple-support excitations was performed with the high-position seismic isolation method using high damping rubber(HDR) bearings. Small-amplitude sinusoidal waves and seismic wave records with various spectral characteristics were applied to the model. The dynamic characteristics of the model and the seismic isolation effect on it were analyzed at varying apparent wave velocities, namely infinitely great, 1000 m/s, 500 m/s and 250 m/s. Besides, numerical simulations were carried out by Matlab software. According to the comparison results, the numerical results agreed well with the experimental data. Moreover, the results showed that the latticed shell roof exhibited a translational motion as a rigid body after the installation of the HDR bearings with a much lower natural frequency, higher damping ratio and only 1/2～1/8 of the acceleration response peak values. Meanwhile, the structural responses and the bearing deformations at the output end of the seismic waves were greatly increased under multiple-support excitations.     

基于形变仪器同震形变波衰减规律的研究

基于黔江台2套倾斜仪记录到的442次同震形变波，对比分析其波谱特征，分区域统计其振幅A与震级M的关系。研究发现:①垂直摆的震动周期和阻尼系数均较小，其波谱信息记录较丰富，适合波谱的时频分析；水管仪的基线较长，阻尼系数较大，抗干扰能力较强，其振幅记录较稳定，适合能量衰减分析；②垂直摆与水管仪的A-M关系均呈指数关系，随着震中距的增加，曲线的拟合程度增强，且指数系数b与ln_a呈负线性相关；③衰减因子k是用来量化同震形变波能量衰减的主要系数，它随着震中距（△≤6000km）增加而增大，且各区域的衰减因子具有一定规律性，对后期建立巨大远震触发型地震模型及其参数设置具有一定指示意义。     

岩土介质随机性对沉积河谷地震动放大效应的影

基于间接边界元法计算沉积河谷对平面P波和SV波的二维散射，着重考察沉积介质波速和材料阻尼的随机性对河谷地震动放大效应。利用蒙特卡罗方法随机模拟产生了波速样本和阻尼样本各30组，给出了不同入射角度和频率P波和SV波入射下河谷随机响应的单频和频谱结果。算例分析结果表明:(1)地表位移响应幅值的变异系数极值均显著大于波速比变异系数，且波速比的随机性对地表位移的影响在体系共振频率处最为明显，地表位移的最大标准差可达7.168；低频情况下，沉积中部地震反应变异性更显著，高频情况下则在沉积河谷边缘变异性最大；(2)入射波角度对地表位移响应变异系数极值的影响不大，但对变异系数空间变化的影响显著；(3)阻尼的随机性对地表位移的影响在低频情况下较小，在高频情况下则较明显，尤其是在沉积河谷的体系自振频率处，其影响最为显著。      

SV波全反射作用下地震动的合成及振动特性

越来越多的研究表明来自基岩的地震波并不是垂直地面向上传播的。地震波在斜入射与垂直入射时所产生的场地效应有很大不同,由于存在全反射现象,SV波在斜入射时产生的场地效应更为复杂。文章基于均匀弹性半空间地震波传播理论,分别推导得到SV波入射角在小于、大于等于临界角时地震动的计算表达式,通过模型算例研究SV波全反射作用下的地震动特性。研究发现：由SV波产生的地震动主要由入射波和反射波构成,滑行波作用可以忽略;地面运动轨迹具有面波旋转振动特点;随着入射角的增大,地面震动从以水平方向振动为主逐渐过渡到以垂直方向振动为主,两个方向的振动均小于入射波峰值的2倍。     

Estimation of peak relative velocity and peak absolute acceleration of linear SDOF systems

In the seismic analysis and design of structures, the true velocity and absolute acceleration are usually approximated by their corresponding pseudo-values. This approach is simple and works well for structures with small damping (say, less than 15%). When the damping of a structure is enhanced for the purpose of response reduction, it may result in large analysis and design errors. Based on theory of random vibration and the established mechanism of seismic response spectra analysis, a method is developed (1) to predict the relative velocity spectra with any damping ratio level directly from the 5% standard pseudo-acceleration spectrum; and (2) to estimate the peak absolute acceleration. The accuracy of both is validated by using two selected ensembles of ground motion records.