A new proposal for simplified design of buried steel pipes crossing active faults

Simplified design methods for obtaining the maximum strain in pipelines crossing active faults proposed by Newmark, Kennedy and Wang have not considered the section deformation of the pipe. In this study, a new simplified method is developed for obtaining the maximum strain in steel pipes crossing faults considering non‐linearity of material and geometry of pipe section. It is assumed that the pipe will bend near the fault and the geometry of pipe in the longitudinal direction will change according to a bent deformation. On the other hand, the relation between maximum strain and bent angle has been obtained using a beam–shell hybrid FEM for different pipe‐fault conditions. The developed method can be used for calculating the maximum strains for fault‐crossing steel pipes with different angles of crossing both in tension and compression, by considering the deformation of the pipe cross‐section. Copyright © 2001 John Wiley Sons, Ltd.     

砖石古塔的地震“修复”及动力学特征初探

汇集了 4例震裂古塔震而复合的有关历史资料。分析认为可探索用人工激震方法对开裂古塔进行修复。从震害资料看出 ,砖石古塔在地震烈度 度以上时将出现破坏。研究了砖石古塔的结构特性 ,提出了对古塔自振周期的计算公式。指出这些研究对古塔的修复、加固及抗震性能评价 ,无疑是有益的     

Determination of soil impedance functions from vibration-test response of a circular foundation

The paper presents the results of the determination from vibration tests of impedance functions for a concrete basemat of a one-quarter scale model of a nuclear power-plant containment building. The tests were designed to excite all rigid-body modes of the foundation. In addition to the impedance functions for all the rigid-body degrees of freedom, natural frequencies and damping for the fundamental modes were estimated. Comparison of the test-determined modal characteristics with corresponding analytical ones based on the Lysmer analog shows that though the latter gives natural-frequency estimates of the right order of magnitude, it does not give acceptable estimates of the damping coefficient. Analytical impedance functions based on a model of a rigid-plate on an elastic half-space were found to have the sam trend as the test-determined ones at lower frequencies, but not at higher frequencies. The utility of test data for verification of analysis is discussed.     

关于在动力机器基础现场模型试验中用拉伸回弹法求地基刚度的探讨

在动力机器基础测试中,拉伸回弹法是一种简易实用的瞬态激振方法;它比常用的球击法具有激振能量大,信号接收效果佳等优点。但运用该法如何求地基刚度的计算却不多见,故本文简要地列出我们推导的算式,以供参考与探讨。     

蒙脱石晶体结构和水结构的矿物物理特征

本文利用矿物物理研究方法对我国内蒙、浙江、甘肃等地的钙基、钠基、镁基蒙脱石的物质成分、晶体结构和层间OH,H_2O的排布结构进行了研究,并获得下列结论: 1.由X衍射和拉曼分子光谱分析深入研究了蒙脱石阳离子配位体结构特征,提出其空间群为C_2/m型。 2.建立了蒙脱石水结构模式,有3种主要类型:①层间大阳离子附近的束缚态水分子;②层间无大阳离子位置上的非束缚态水分子;③颗粒表面依靠氢键相连的水分子集合体。 3.利用群理论,提出了蒙脱石OH~-的振动模式,由振动分析指出蒙脱石中OH~-具有12个振动模式。     

Ambient vibration studies for system identification of tall buildings

The performance of a building under wind and seismic loads depends on stiffness and mass distribution, and may be estimated using finite element codes. Experience has, however, shown that such finite element models often fail to predict accurately the fundamental natural frequencies. Usually the frequencies will be underestimated, that is the building will turn out to be stiffer than anticipated, meaning the design would usually be conservative. On the other hand, effects like torsional eccentricity and foundation compliance may not be correctly modelled, which could be less desirable. A full understanding of linear performance under lateral loads can be obtained through experimental evaluation of the vibration modes. Traditionally only a limited range of modal analysis procedures and software has been applied to civil applications and the ‘special case’ where no input forces can be measured has been the usual situation for large civil structures. Recent developments in system identification, which is the set of procedures to build mathematical models of the dynamic structural systems based on measured data, have added significantly to the potential of ambient vibration or ‘output only’ testing. The aim of the research reported here has been to apply and evaluate the procedures on typical buildings. The procedures are briefly explained and two experimental programmes are then described; a long‐term tremor monitoring exercise on a 280m office tower and an ambient vibration survey of a smaller office block. The different forms of response data are examined to study the performance of the analysis procedures and expose benefits and limitations in their use. There is a growing interest in output‐only modal analysis procedures in civil engineering. The experience reported in this paper has shown that quick and reliable estimation of mode shapes and frequencies can be obtained, even with small amounts of data. Judgement of modal participation and damping ratios requires more detailed study yet the results are at least as convincing as existing and relatively limited frequency domain methods. Copyright © 2002 John Wiley & Sons, Ltd.     

Robust active vibration suppression control with constraint on the control signal: application to flexible structures

A unified mathematical framework, sustained by experimental results, is presented for robust controller design taking into account the constraint on the control signal. The design procedure is exemplified for an active vibration suppression control problem with applications to flexible structures. The considered experimental set‐up is a three‐storey flexible structure with an active mass driver placed on the last storey. First, the considered flexible structure is identified and the model's parametric uncertainties are deduced. Next, control constraints are presented for the robust control design problem, taking into account the restriction imposed on the control signal. Finally, the effectiveness of the control system is tested through experiments, when the input disturbance is assumed to be a sinusoidal one as well as a historical earthquake record (1940 El Centro record). Copyright © 2003 John Wiley & Sons, Ltd.     

Studies on seismic reduction of story‐incresed buildings with friction layer and energy‐dissipated devices

A new type of energy‐dissipated structural system for existing buildings with story‐increased frames is presented and investigated in this paper. In this system the sliding‐friction layer between the lowest increased floor of the outer frame structure and the roof of the original building is applied, and energy‐dissipated dampers are used for the connections between the columns of the outer frame and each floor of the original building. A shaking table test is performed on the model of the system and the simplified structural model of this system is given. The theory of the non‐classical damping approach is introduced to the calculation analyses and compared with test results. The results show that friction and energy‐dissipated devices are very effective in reducing the seismic response and dissipating the input energy of the model structure. Finally, the design scheme and dynamic time‐history analyses of an existing engineering project are investigated to illustrate the application and advantages of the given method. Copyright © 2003 John Wiley & Sons, Ltd.     

公路车辆产生振动波的衰减研究

精密仪器对周围振动环境要求很高，必须摆放在相对安静的地点。对公路两侧不同车辆的振动情况进行了实验研究。采用三分量检波器和24道工程地震仪进行测量。实验结果表明，测点上振动幅度随与公路的距离增加而减小，可用γ=Ar^α，y=Ar^1.71249表示，振动频率为10～20Hz。在今后类似的研究中，可以根据这一规律来确定仪器的安装地点，作10～20Hz带通滤波来消除汽车的干扰。