导管架式海洋平台结构阻尼隔振体系及其减振效果分析   总被引：10，自引：2，他引：10  

欧进萍  龙旭  肖仪清  吴斌 《地震工程与工程振动》2002,22(3):115-122

导管架式海洋平台结构是当前应用最广的一种平台结构形式。本文研究导管架式海洋平台结构阻尼隔振体系及其减振效果。针对导管架式海洋平台结构的型式与特点，为了充分发挥阻尼器的耗能减振作用，提出了在平台结构导管架端帽和甲板之间设置柔性阻尼层的新型阻尼隔振方案。针对渤海JZ20－2MUQ平台结构，建立了海洋平台结构阻尼隔振体系简化计算模型，研究了隔振层参数与结构阻尼比的关系以及它们对结构整体和隔振层层间相对位移的控制效果；进行了多种冰荷载工况和地震工况的数值模拟。结果表明，阻尼隔振方案是导管架式海洋平台结构的一种有效的减振措施。  相似文献   

南京地区新近沉积土的动剪切模量和阻尼比的初步研究   总被引：9，自引：1，他引：9  

刘雪珠  陈国兴  胡庆兴 《地震工程与工程振动》2002,22(5):127-131

本文通过对南京地区两个工程场地漫滩相成因的砂土和淤泥质粉粘土与粉砂互层土的自振动柱试验结果进行分析，探讨了围压对剪切模量G及阻力比λ的影响，通过与Seed和Idriss建议的砂土G/Gmax-γ和λ-γ曲线变化范围的对比，认为不能简单地把淤泥质粉质粘土与粉砂层土当作砂土或粉质粘土对待。  相似文献   

滑带土动力学性质试验研究   总被引：1，自引：0，他引：1  

晏鄂川  刘汉超  唐辉明 《工程地质学报》2003,11(3):318-322

为了研究地震高烈度区老滑坡的复活变形原因,本文对滑坡滑带土的动力学特性进行了系列研究。本次试验采用扰动土样,制样基本物理指标按滑带土的现场测试指标确定,在不固结不排水条件下,运用MTS810Teststar程控液压伺服土动三轴仪对单个样品逐级放大动应力的分级试验方法进行。侧向压力 (围压 )分别采用 100kPa、20 0kPa、300kPa三级,通过施加轴向振动荷载 (力 )模拟地震作用,振动波形为正弦波,频率为 1Hz,振幅随试样性质确定。研究结果表明,滑带土在动荷载作用下的动力学性质与其静荷载作用下的力学性质有着较大的差异,主要表现在滑带土的动应力与动应变关系的非线性、滞后性及变形积累特点,动弹性模量与动强度的显著降低以及动阻尼比的显著增大特性。这揭示了动力作用下的滑坡复活原因之一,同时为滑坡稳定性评价和动力作用下的变形机制模拟分析提供了基础资料,也为分析滑带土动力本构模型提供了基本内容。  相似文献   

长江河源区的河水主要元素与Sr同位素来源   总被引：20，自引：1，他引：20  

赵继昌  耿冬青  彭建华  刘丛强  B.Dupre  J.Gaillardet  李文鹏  何庆成 《水文地质工程地质》2003,30(2):89-93,98

长江源区河水化学成分来自雨雪、蒸发盐岩、碳酸盐岩和硅酸盐岩。主要支流楚玛尔河、北麓河的主要阳离子为Na 、Ca2 和Mg2 ,占阳离子总量的97%以上.Ca Na,Mg Na,K Na的比值较低,87Sr 86Sr为0 709180±20～0 710280±11,河水成分以蒸发岩类溶解为主。发源于唐古拉山北坡的长江源头,及其支流主要阳离子为Ca2 ,Mg2 ,Na 占阳离子总量的97%以上,Ca Na,Mg Na,K Na的比值较楚玛尔河等河流高,87Sr 86Sr为0 708954±20～0 710455±18,表现为以碳酸盐岩和硅酸盐岩的溶解为主。计算表明,长江河源区河水中主要化学成分来自蒸发岩中Na 和Cl-,在河流水化学成分中占比例最大,长江河水中Cl-含量从河源区向下游明显逐渐减小,反应出河源区高寒干旱环境下河流蒸发岩的化学侵蚀作用较强的特征。  相似文献   

地震台阵滤波及子台分布对聚束效果的影响(Ⅱ)——子台分布及聚束效果的分析          下载免费PDF全文

刘旭  朱元清  佟玉霞 《地震工程学报》2003,25(4):293-297

本假设对于确定的相关系数及子台间距存在一个相干波长，将不同频率、震中距的相关性变化的原因归纳为视波长的变化．对近事件而言，几乎不存在相关系数十分理想的子台间距的区间范围．对非理想相关的台阵，应用S．Mykkeltveit等介绍的增益公式来预测台阵的增益，其效果与实际情况吻合的较好．论述了区域台阵与侦察远处事件的台阵有诸多不同之处．  相似文献   

Distribution of L_g coda Q in the Chinese continent and its adjacent regions     

丛连理  胡家富  傅竹武  温一波  康国发  吴小平 《中国科学D辑(英文版)》2003,46(6)

In continent Lg is usually one of the predominant phases recorded by short-period or broad-band seismometers. A ray-theoretical approach shows that Lg wave is the superposition of higher-mode surface waves propagating in the continental crust[1—4]. The g…  相似文献   

The development of Nemurella pictetii Klapálek (Plecoptera: Nemouridae) in two springstreams in central Europe     

Andrei Nesterovitch  Peter Zwick   《Limnologica》2003,33(4):231-243

From April 1997 to June 1998 Nemurella pictetii populations were regularly sampled in two springstreams at 220 and 850 m a.s.l., respectively, in Hesse (Germany), at approximately 51°N. Random samples of larvae were taken at three week intervals during the vegetation period, and once a month during winter. Sex, instar, body length, head capsule width and wing pad length of all larvae were recorded. Temperatures were recorded every hour, temporal patterns of temperature agreed closely between sites. Mean winter lows were 3.9 °C at both sites, the mean summer high was 11.9 °C at the lower site, as opposed to 9.6 °C at the mountain site.At both sites, adult emergence started in May. At the mountain site, recruitment started in late July and continued into autumn. There was cohort splitting in the young generation. Some individuals grew rapidly until October–November, but last instar larvae first appeared in March the next year. 1600 degree-days above 0 °C were accumulated during complete development. At the lower site, recruitment began in early July, and cohort splitting also occurred. Fast growing summer recruits emerged as adults in late August, having accumulated only 700 degree-days (above 0 °C). Their offspring hatched in November-December and emerged the next spring, having accumulated also only 700 degree-days. However, only part of the population was bivoltine. Many of the summer recruits grew more slowly and accumulated close to 1900 degree days until they emerged the next spring, together with the offspring of their own fast-growing siblings. Dependence of growth rate on temperature could not be estimated and appears to vary with daylength. For example, 3–6 °C support growth and development provided daylength exceeds 10 hrs of light, or is rising.At both sites and in all cohorts individuals emerging earliest were larger than later emerging ones. The size decline is significantly correlated with number of days after the winter solstice. For the first time it is shown that the decline does not occur shortly before adult emergence but actually takes place several instars before the last. Size differences are then carried on, and amplified, during subsequent molts, until adulthood. The literature presently relates seasonal size declines of insects to high or rising temperatures experienced by larvae approaching adulthood. Our data show that, at least in Nemurella, this explanation fails. On average, females were distinctly larger than males. Differences in mean last instar size were noticed also between sites and years. They remain presently unexplained. The mean sex ratio in both populations was close to 1:1.  相似文献   

Nonlinear Rate Dependent Model of High Damping Rubber Bearing     

Robert Jankowski 《Bulletin of Earthquake Engineering》2003,1(3):397-403

The accurate analysis of the response of isolated structures requires the application of appropriate models of isolation devices. The purpose of this paper is to analyse a nonlinear strain rate dependent model of a high damping rubber bearing which simulates the horizontal behaviour of the device under specified vertical load using a nonlinear elastic spring-dashpot element. The effectiveness of the model is checked by fitting the experimental data concerning three different rubber bearings. The results of the study show that the model can simulate the bearing behaviour over a wide shear strain range with small simulation errors. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Optimum multiple tuned mass dampers for structures under the ground acceleration based on the uniform distribution of system parameters     

Chunxiang Li  Yanxia Liu 《地震工程与结构动力学》2003,32(5):671-690

The five MTMD models, with natural frequencies being uniformly distributed around their mean frequency, have been recently presented by the first author. They are shown to have the near‐zero optimum average damping ratio (more precisely, for a given mass ratio there is an upper limit on the total number, beyond which the near‐zero optimum average damping ratio occurs). In this paper, the eight new MTMD models (i.e. the UM‐MTMD1～UM‐MTMD3, US‐MTMD1～US‐MTMD3, UD‐MTMD1 and UD‐MTMD2), with the system parameters (mass, stiffness and damping coefficient) being, respectively, uniformly distributed around their average values, have been, for the first time here, proposed to seek for the MTMD models without the near‐zero optimum average damping ratio. The structure is represented by the mode‐generalized system corresponding to the specific vibration mode that needs to be controlled. Through minimization of the minimum values of the maximum dynamic magnification factors (DMF) of the structure with the eight MTMD models (i.e. through the implementation of Min.Min.Max.DMF), the optimum parameters and values of Min.Min.Max.DMF for these eight MTMD models are investigated to evaluate and compare their control performance. The optimum parameters include the optimum mass spacing, stiffness spacing, damping coefficient spacing, frequency spacing, average damping ratio and tuning frequency ratio. The six MTMD models without the near‐zero optimum average damping ratio (i.e. the UM‐MTMD1～UM‐MTMD3, US‐MTMD1, US‐MTMD2 and UD‐MTMD2) are found through extensive numerical analyses. Likewise, the optimum UM‐MTMD3 offers the higher effectiveness and robustness and requires the smaller damping with respect to the rest of the MTMD models in reducing the responses of structures subjected to earthquakes. Additionally, it is interesting to note, by comparing the optimum UM‐MTMD3 with the optimum MTMD‐1 recently investigated by the first author, that the effectiveness and robustness for the optimum UM‐MTMD3 is almost identical to that for the optimum MTMD‐1 (without inclusion of the optimum MTMD‐1 with the near‐zero optimum average damping ratio). Recognizing these performance benefits, it is preferable to employ the optimum UM‐MTMD3 or the optimum MTMD‐1 without the near‐zero optimum average damping ratio, when installing the MTMD for the suppression of undesirable oscillations of structures under earthquakes. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Steel frames with bracing mechanism and hysteretic dampers     

M. C. Phocas  A. Pocanschi 《地震工程与结构动力学》2003,32(5):811-825

A new earthquake resistant structural system for multi‐storey frame structures, based on a dual function of its bracing components, is developed. This consists of a hysteretic damper device and a cross‐bracing mechanism with a kinetic closed circuit, working only in tension, so that cable members can be used for this purpose. Solutions are presented regarding the connections' design of three types of structural frame system, that are concerned throughout the study: braced moment free frame, braced moment resisting frame with moment free supports, and with moment resisting supports. The dynamic behaviour of the system is investigated on the basis of an SDOF model, and based on the response spectra method an approximate design approach of the controlled structures is shown. From the time history analysis of the structural systems for the El Centro earthquake the areas of appropriate stiffness relations of the frames to the hysteretic dampers and the cable braces are deduced, so that the energy dissipation of the system may be controlled by the damper‐cable bracing mechanism. Based on the results of these studies, a predesign approach is developed for the implementation of the control system in frame structures. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献