新型压电变摩擦阻尼器的研发与性能试验

本文采用商用标准件叠层压电驱动器和圆形摩擦盘,研发了能提供水平任一方向可调摩擦阻尼力的新型压电变摩擦阻尼器,能与圆形隔震垫协同工作复合而成智能隔震系统.文中首先提出了新型压电阻尼器的基本结构,制作了试验室比例的模型;其次针对压电驱动器变形在微米数量级的特点和约束钢架的刚度特性,提出了基于有限元分析的形状系数和可调正压力计算方法.并用约束钢架变形试验验证了有限元分析的正确性;最后通过阻尼器性能试验提出了连续型的阻尼力计算模型,一种适合于实际工程应用的摩擦阻尼力模型.提出的新型压电摩擦阻尼器构造简单,阻尼力调节方便,响应速度快,特别是便于进一步增大阻尼力调节倍数,能够较大地推动压电阻尼器实用化进程.     

黏性土的动剪切模量比和阻尼比与剪应变关系的统计分析

动剪切模量比和阻尼比是土体重要的动力特性参数,这两种参数取值的合理性对场地地震响应分析的结果有重要影响.为进一步完善黏性土的动剪切模量比和阻尼比随剪应变的变化关系的研究,给出了新的计算模型和推荐曲线.新曲线的计算模型基于Davidenkov模型和新的阻尼比计算模型,通过对搜集的大量黏性土数据进行非线性回归分析后得到.将分析结果与已有国内外学者的成果进行对比,验证了新计算模型具有较好的可靠性和工程实用性.     

巷道超前探测散射成像处理技术

国内外在隧道施工过程中已开始应用反射波法超前探测前方小构造,如断层、陷落柱.由于前方的断层面、陷落柱界面起伏不平,所以接收到的反射波能量较弱,难以精确成像,而基了惠更斯原理的散射成像方法能充分利用地震信号的全波场信息,具有较好的偏移成像效果,散射成像为巷道超前探测提供了一种可行的成像方法.笔者通过建立巷道超前探测模型,分析了散射成像处理技术的效果,验证了散射成像方法应用于巷道超前探测的可行性.     

港口内靠码头系泊船运动的计算

本文以英国南海岸处Ｓｈｏｒｅｈａｍ港内系泊船为例，研究了港口内靠码头系泊船运动的数值计算问题。该船的实船实验和模型实验已经完成，为验证本文计算结果提供了依据。运动方程在时域内求解。在计算船体脉冲响应函数时，引入了船体阻尼系数在频率很低时的渐近表达式和一迭代算法。分析了港内共振波浪和其对船体的作用力。讨论了靠码头系泊船运动的非线性特征。计算结果与实验结果符合很好。     

Study of the radon concentrations in drinking water from three main cities of Shaanxi Province,China

This paper presents the results of radon concentration measurements in the drinking water from the municipal water supply system and private wells of Xian, Xianyang and Baoji city of Shaanxi province of China. The measurements were carried out on 38 samples. Radon levels in drinking water in Xian, Xianyang and Baoji were found to be 5.78, 13.04 and 15.01 k Bq m^–3, respectively. The AM radon concentration of private well water from Xianyang and Baoji is 28.84 k Bq m^–3 and 38.85 k Bq m^–3, respectively, which is 2.56 times and 3.14 times as high as that of tap water radon, respectively. The radiation risk of radon in water would be due to degassing and not due to drinking water. The domestic use of showers, humidifiers, and cooking, washing up, laundering, etc. may lead to an additional increase of the radon concentration in the indoor air. The observed radon concentration in drinking water from three main cities of Shaanxi Province can contribute to a 4.86 to 32.63% increase in indoor radon concentration and can cause 0.068±0.016 mSv y^–1 to 0.177±0.045 mSv y^–1 extra annual effective dose to males, 0.060±0.014 mSv y^–1 to 0.155±0.039 mSv y^–1 to females. The mean annual effective dose equivalents to males and females of Xianyang and Baoji from well water account for 25.94 to 39.75% of environmental radon and radon daughters annual effective dose equivalents. The radon concentrations in the well water from Xianyang and Baoji will bring a definite additional risk to the population.     

MHD waves in coronal loops with a shell

We consider a model of a coronal loop in the form of a cord surrounded by a coaxial shell. Two slow magnetosonic waves longitudinally propagate within a thin flux tube on the m=0 cylindrical mode with velocities close to the tube velocities in the cord and the shell. One wave propagates inside the cord, while the other propagates inside the shell. A peculiar feature of the second wave is that the plasma in the cord and the shell oscillates with opposite phases. There are two fast magnetosonic waves on each of the cylindrical modes with m>0. If the plasma density in the shell is lower than that in the surrounding corona, then one of the waves is radiated into the corona, which causes the loop oscillations to be damped, while the other wave is trapped by the cord, but can also be radiated out under certain conditions. If the plasma density in the shell is higher than that in the cord, then one of the waves is trapped by the shell, while the other wave can also be trapped by the shell under certain conditions. In the wave trapped by the shell and the wave radiated by the tube, the plasma in the cord and the shell oscillates with opposite phases.     

Simple models for estimating period‐shift and damping in soil

This study describes the development of a simple, heuristic manual calculation procedure for estimating the site period‐shift factor and soil damping ratio, with appropriate considerations for the level of shaking, impedance contrast between soil and bedrock interface and the plasticity of the soil layers. Essentially, the analogy of a building shear‐frame has been used to represent the seismic response behaviour of a soil column. The proposed procedure has been verified by comparing the predictions with results obtained directly from non‐linear shear wave analyses of soil column models. Copyright © 2006 John Wiley & Sons, Ltd.     

Simplified methods for design of base‐isolated structures in the long‐period high‐damping range

A recent trend in the design of base‐isolated structures is the extension of the natural period and the incorporation of high damping. This paper shows that the existing simplified methods perform less accurately in this field of application, mainly due to inappropriate use of spectral data and insufficiently adjusted equivalent models. The paper proposes new period‐dependent concepts to reduce pseudo‐acceleration spectra and to transform these values into total accelerations with respect to the viscous damping ratio. The model of equivalent damping is adjusted to reflect several period‐dependent effects. The estimation of the accelerations in MDOF systems is based on additional period shifts. All modifications are derived for a simplified linear approach based on eigenforms, and a non‐linear approach based on pushover and capacity spectrum analysis. To illustrate observed problems and to demonstrate the capabilities of the proposed concepts, example structures are studied in detail. Furthermore, intensive statistical tests prove the effectiveness of the modifications in a wide parameter range and show considerable improvements over traditional approaches. Copyright © 2005 John Wiley & Sons, Ltd.     

Inversion of waveforms from. Xiangtang borehole seismic array for soil dynamic property

In order to understand the site soil response of the Xiangtang borehole seismic array under real strong ground motion, reveal the site response, verify the technique of borehole exploration, and improve the precision of in-situ test and laboratory test, this paper presents a new approach, which is composed of two methods. One is the layered site seismic response method, whose layer transform matrix is always real. The other is a global-local optimization technique, which uses genetic algorithm (GA)-simplex method. An inversion of multi-component waveforms of P, SV and SH wave is carried out simultaneously. By inverting the records of three moderate and small earthquakes obtained from the Xiangtang borehole array (2# ) site, the soil dynamic characteristic parameters, including P velocity, damping ratio and frequency-dependent coefficient b, which has not been given in previous literatures, are calculated. The results show that the soil S wave velocity of the Xiangtang 2# borehole is generally greater than that obtained from the 1994 in-situ test, and is close to the velocity of the 3# borehole, which is more than 200 m away from the 2# borehole. Meanwhile, perceptible soil nonlinear behavior under peak ground motion of about 60×10-2m/s2 is detected by the inversion analysis. The presented method can be used for studying the soil response of other borehole array sites.     

附加或不附加粘滞阻尼墙的RC框架试验与分析

本文阐述了附加或不附加粘滞阻尼墙的2个相同的RC框架模型振动台试验和理论分析的情况.这2个钢筋混凝土框架模型为3层1跨两开间,几何相似关系大致为1：2.将阻尼墙附加到一个RC框架模型当中,先后对附加或不附加阻尼墙的2个相同的RC框架模型进行振动台试验.试验结果表明,阻尼墙有效减小了框架模型的地震反应.对耗能框架模型和普通框架模型进行了弹性和弹塑性时程分析,计算结果和试验结果吻合良好.改变阻尼墙的参数进行分析,结果表明选取合适的阻尼墙参数,才能达到最好的耗能减振效果;适当减小层间位移较小处的阻尼墙参数,对减振效果影响很小而又能节省投资.