一种求解地下结构顶板频率和振型的方法

采用欧拉梁横向自由振动理论,发展了一种求解浅埋地下结构顶板频率和振型的方法。鉴于地下结构顶板频率求解问题的复杂性,首先将该问题假定为平面应变问题求解,推导出浅埋地下结构项板梁的自由振动方程;然后根据顶板梁的边界条件,得到了顶板梁的频率方程,从而得出了顶板梁的频率和振型;进一步得出了墙体转动刚度对顶板频率影响的规律,即转动刚度对顶板低频影响较小,对高频影响较大。还综合考虑土体刚度随埋深的变化和由于土体成拱引起的土体附加质量的变化,研究了结构顶板频率随埋深的变化。这些结果可以为地下结构的动力计算提供参考。     

饱和南京细砂永久应变势模型的试验研究

土单元永久应变势的预测模型是土动力学的重要研究内容之一。现有的土单元永久应变势模型没有反映振动孔压增长的影响,难以合理解释地震动作用引起的饱和砂土地基永久变形一般是由土层软化或再固结变形所致的机理。基于饱和南京细砂永久变形动三轴试验结果的有效应力状态分析,研究了试样的永久变形与振动孔压增长的关系,建立了一个能反映振动孔压增长影响的土单元永久应变势模型,给出了土单元永久应变势的数学表达式,分析了土单元永久应变势模型参数的影响因素。初步的验证性试验表明:模型预测与试验测得的试样永久应变势与振动孔压增长曲线比较接近,说明该模型具有一定的合理性。     

摩擦摆隔震双层球面网壳结构的多维地震响应

将摩擦摆(FPS)引入到网壳结构的隔震控制中。文中首先阐明了FPS的工作机理和本构关系,建立了FPS隔震网壳结构的振动方程。通过双层球面网壳结构的数值算例考察了隔震和无控结构在单向和三向地震作用下的振动响应以及FPS的控制效果。研究结果表明,FPS具有良好的隔震和耗能效果,可有效地应用于球面网壳结构的振动控制。     

Ground motion spatial variability effects on seismic response control of cable-stayed bridges

The spatial variability of input ground motion at supporting foundations plays a key role in the structural response of cable-stayed bridges (CSBs); therefore, spatial variation effects should be included in the analysis and design of effective vibration control systems. The control of CSBs represents a challenging and unique problem, with many complexities in modeling, control design and implementation, since the control system should be designed not only to mitigate the dynamic component of the structural response but also to counteract the effects of the pseudo-static component of the response. The spatial variability effects on the feasibility and efficiency of seismic control systems for the vibration control of CSBs are investigated in this paper. The assumption of uniform earthquake motion along the entire bridge may result in quantitative and qualitative differences in seismic response as compared with those produced by uniform motion at all supports. A systematic comparison of passive and active system performance in reducing the structural responses is performed, focusing on the effect of the spatially varying earthquake ground motion on the seismic response of a benchmark CSB model with different control strategies, and demonstrates the importance of accounting for the spatial variability of excitations.     

台湾花莲软玉的组构及振动光谱特征

以台湾花莲地区所产的绿色软玉为研究对象,利用电子探针(EPMA)、X射线粉晶衍射(XRD)、傅立叶变换红外光谱(FTIR)、激光拉曼光谱(RAMAN)等分析测试方法,对绿色软玉的物相、组构及振动光谱特征进行了研究。结果表明,该绿色软玉的主要矿物成分为透闪石,含少量的铬铁矿以及含Cr 钙铝榴石。软玉以纤维交织变晶结构为主,部分透闪石纤维体沿其片理方向定向排列,偶见铬铁矿骸晶及交代假像结构。对花莲绿色软玉的红外吸收光谱及拉曼光谱进行了表征,并对其振动光谱的归属作了探讨。     

平稳小波变换在地震反射资料中面波压制的应用

提高地震信号的分辨率是地震勘探要解决的一项主要任务,而提高地震信号的信噪比是提高地震信号分辨率的先决条件。要提高地震资料的信噪比,需要去除地震资料中的相干噪声和随机噪声。本文介绍了平稳小波变换结合阈值压制面波干扰的方法,通过实际地震记录的处理证实了该方法的有效性。     

质点振动速度监测在爆破掘进工程中的应用

工程爆破施工过程中如何控制其对周围建筑物、正在施工项目和处于养护龄期内的混凝土结构的影响一直是爆破施工中的实际问题,直接关系爆破施工的单响药量和施工进度。隧道爆破掘进施工中为了追求施工进度,往往在爆破方案中使用较大的单响装药量,从而忽略了大药量爆破产生的冲击波效应对隧道岩壁、已有结构的破坏,本文简单介绍了施工前或施工中,进行质点振动速度监测的实际应用。     

面波压制的TT变换法

在地震勘探中,面波的频率比其他有效地震波的频率低,往往被视作干扰波而需要压制,以突出有效波。TT(time-time)变换具有很好的频率聚集能力,它将高频信号聚集在TT变换域的对角线位置,通过提取TT变换域的对角线附近的元素,就可以压制低频面波,突出反射波。对物理模型和实际数据进行处理,并与传统的高通滤波方法进行对比,结果表明:TT变换实际上是S变换的延伸,与S变换有着密切的联系,有无损可逆性,而且具有很好的频率聚集能力。TT变换在压制面波方面有较好的效果,但在提取高频、压制低频的同时,漏掉了一些低频的有效信号,同时也保留了部分高频干扰,这是TT变换在信号分析中的不足之处。因此,在实际应用中应将TT变换和S变换结合起来,避免一些解释上的假象。     

Effect of anti-slosh baffles on free liquid oscillations in partially filled horizontal circular tanks

An exact two dimensional hydrodynamic analysis based on the linear potential theory is introduced to study the free liquid sloshing characteristics of transverse oscillation modes in a non-deformable horizontal circular cylindrical baffled container which is filled to an arbitrary depth with an inviscid incompressible liquid. Three common baffle configurations are considered: a pair of internal rigid horizontal side baffles of arbitrary extension installed at the free liquid surface, and a surface-piercing or a bottom-mounted vertical rigid baffle of arbitrary extension positioned along the tank vertical axis of symmetry. The problem solution is obtained by the method of successive conformal coordinate transformations, leading to standard truncated matrix eigenvalue problems on simple (rectangular) regions which are then solved numerically for the resonance eigen-frequencies. The effects of liquid fill level, baffle arrangement and length upon the three lowest antisymmetric and symmetric sloshing frequencies and the associated hydrodynamic pressure mode shapes are examined. Also, convergence of the adopted approach with respect to the fill condition, and baffle type/extension is discussed. Limiting cases are considered and the validity of results is established in comparison with the data in the existing literature.     

非均匀流中立管涡激振动模型预测分析

文中分析了非均匀流中,张紧式海洋立管的涡激振动,采用新的加速度耦合尾流振子模型作为预测细长海洋工程柔性结构的计算工具,将预测结果中的横向位移包络线及最大幅值与实验观测值、shear7软件计算值进行了对比,可以发现模型的计算结果与实验观测结果吻合得很好.