考虑弯曲转角的框剪结构-TMD减震体系数值优化设计

提出了一种适用于框剪结构的TMD减震体系优化设计方法。将结构简化为连续-离散的悬臂梁模型,该模型不但能体现结构的剪切变形,而且能充分考虑结构弯曲变形产生的弯曲转角对TMD动力特性的影响。使用Rayleigh-Ritz法分析结构动力特性,在此基础上,基于结构的性能目标使用遗传算法对TMD体系进行数值优化设计。最后,针对某框剪结构的TMD减震体系优化设计问题进行了研究,研究结果证明了将TMD质量比作为优化参数的正确性。通过与传统Den Hartog参数对比发现,此方法设计的TMD质量更小且控制效果更好。     

考虑土-结构动力相互作用的TMD结构减震控制

本文分析了TMD(Tuned mass damper)在刚性地基和柔性地基情况下的减震控制机理,以某6层钢筋混凝土框架结构为研究对象,分别考虑了土-结构动力相互作用对无TMD控制结构的影响,场地条件对TMD减震控制性能的影响和土-结构动力相互作用对TMD减震控制性能的影响。通过分析得出TMD控制系统的减震效果除了与输入地震动特性有关外,还与场地条件、上部结构和基础的动力特性等因素有关。如果土-结构动力相互作用体系的自振周期远离输入地震动的卓越周期,则相互作用体系的地震响应较小。地基土越软,框架建筑结构层间相对位移地震响应也就越小。如果考虑土-结构动力相互作用效应的影响设计TMD调频系统的自振周期,则TMD的控制效果会有一定程度的提高。     

粘滞阻尼器对空间结构的振动控制效应

采用三向地震波输入对西北高烈度地震带某体育馆进行非线性时程分析,研究粘滞阻尼器对大跨空间结构抗震加固的机理和效果。以节点水平向位移、构件内力作为屋盖振动控制目标,楼层位移及剪力作为下部结构振动控制目标。时程分析表明：不同地震波作用时上部屋盖减震控制效果均较好;但下部结构减震控制对地震波频谱特性较为敏感;设置粘滞阻尼器对不同地震烈度下整体结构的动力响应均能起到有效控制作用;屋盖结构上均匀布置阻尼器比集中布置减震效果好;空间结构振型复杂,减震分析须考虑上下部结构的耦合作用。研究成果可为大跨空间结构采用粘滞阻尼器减振控制提供参考。     

TMD基础隔震混合减震体系地震响应研究

针对基础隔震体系遭受强地震时隔震层位移较大问题,提出了将调谐质量阻尼器(TMD)与基础隔震技术联合应用,形成一种新型的混合减震体系,以此控制隔震层的位移,同时减小上部结构响应。以一栋七层基础隔震体系为仿真算例,分别分析地震激励下基础隔震结构、调谐质量阻尼器(TMD)设置于基础隔震结构底层和顶层的混合减震体系地震响应。仿真结果表明:附加调谐质量阻尼器(TMD)不但能够有效减小隔震层的地震响应,同时对上部结构的响应也有不同程度的减小;对于附加调谐质量阻尼器位于底层而言,质量调谐阻尼器(TMD)位于顶层能够更有效的减小基础隔震体系的地震响应。     

AP1000核电站屏蔽厂房BIS-TMD新型结构及其抗震性能研究

针对核电站传统结构在服役期间可能出现的地震破坏,应用建筑结构隔震减震技术,将AP 1000核电站的非能动安全理念推广到结构抗震领域,提出了屏蔽厂房基础隔震-调频质量阻尼(BIS-TMD)新型结构,大幅度地提高了屏蔽厂房的抗震安全。基于屏蔽厂房各部分的功能要求,修改了屏蔽厂房各部分的连接方式,在增加附加质量很小的情况下,实现了本新型结构。基于AP 1 000基础隔震结构的研究成果,构建了本新型结构的参数优化模型,给出了TMD支座的选型参数,研究了本新型结构的减震机理。通过与传统结构、基础-隔震结构和TMD结构等比较,表明了本新型结构综合了BIS和TMD的优点,能够很好地抵御地震大小和频谱、重力水箱水质量、TMD支座和BIS支座力学性能等因素变化对减震效果的影响;具有显著的减震效果,稳定的抗震鲁棒性和良好的场地适用性,能够很好地满足核电站抗震安全的要求。     

TMD对密频结构减震的参数优化及性能研究

就多模态密集频率结构的减震问题,建立分布式TMD(tuned mass dampers)对地震激励下结构多模态振动减震的力学模型进行研究,并将其表达为闭环静力反馈控制的形式。我们研究具有较高优化效率的基于H2性能的梯度法,实现对多模态调谐减震的TMD参数的整体优化。以构建的理想三自由度密频结构为例,定义无量纲响应指标,以扫频激励的方式求得具有相对普适性的优化控制权重,进而采用基于H2性能的梯度法优化得到分布式TMD的最优参数;针对具有不同谱特性的地震动激励进行减震分析,并与经典TMD方法对比,结果表明基于H2性能的梯度法优化所得的TMD针对多模态密频结构将具有更好的减震性能。     

考虑土与结构相互作用效应的结构减震控制大型振型台模型试验研究

本文设计并完成了考虑土与结构相互作用的结构减震控制大型振动台模型试验，通过对四种结构形式的对比试验。探讨了土与结构相互作用（SSI）效应对结构地震反应的影响以及调谐质量阻尼器（TMD）在刚性和柔性地基条件下对主体结构的减震效应。通过比较同一地震动作用下主体结构在刚性和柔性两种地基条件下的地震反应，可知：SS效应具有降低和提高结构减震控制效果的双重作用，其综合效果与输入地震动的频谱特性，加速度峰值大小有关。由于SSI效应在结构地震反应中发挥着双重的作用，因而使得基于刚性地基假定了设计的TMD减震控制系统在柔性地基条件下的控制效果不太理想，甚至会出现负面效应。本文还探讨了在生地基条件下影响减震控制效果的一些因素。     

带TMD的结构基于动力可靠性约束的优化设计

本文在运用复模态法求得多自由度带TMD结构随机地震响应解析解的基础上．采用基于动力可靠性约束的优化设计方法对TMD装置参数的优化取值进行了系统研究,以结构最大位移响应的期望值为目标函数,以TMD装置响应的动力可靠性为约束条件,运用罚函数法获得到TMD装置的优化设计参数．并给出了算例,从而建立了带TMD结构基于动力可靠性约束的抗震优化设计的一整套方法,本文方法也可用于基础隔震结构、带TLD减震结构以及带TMD和TLD抗风结构的优化设计。     

新型半主动调谐质量阻尼器减震性能的数值模拟

为了改良被动式调谐质量阻尼器(TMD)对建筑结构的减震效果,本文提出了一种新型的可实时调节频率和电涡流阻尼的半主动调谐质量阻尼器(SATMD)。由Hilbert-Huang变换(HHT)识别出结构的瞬时频率,通过基于HHT的控制算法实时调节SATMD的质量进行频率的调谐;通过基于线性二次型高斯(LQG)的控制算法实时调整磁导间距来调节电涡流阻尼系数。为了验证SATMD对建筑结构的减震效果,以一单自由度结构模型为例进行地震响应模拟,同时采用一经优化设计的被动TMD作为对比,并考虑由于主结构的累积损伤等引起自身频率下降而造成被动TMD的去谐效应。以主结构的加速度和位移时程峰值、整体均方根值及TMD的耗能性能作为评价指标,对比了SATMD在主结构发生损伤前后对被动TMD的改良效果。数值模拟结果表明,在主结构发生损伤前后,SATMD均比经优化设计的被动TMD有更好的减震效果及耗能能力。     

电磁耗能TMD结构减震效率的振动台试验研究

通过钢框架TMD减震的振动台模型试验，测试电磁耗能TMD新装置的减震耗能性能。大量试验结果表明：利用电磁涡流耗能原理的TMD新装置具有良好的结构减震效率。     

A Monte Carlo study of rainfall forecasting with a stochastic model

A procedure for short-term rainfall forecasting in real-time is developed and a study of the role of sampling on forecast ability is conducted. Ground level rainfall fields are forecasted using a stochastic space-time rainfall model in state-space form. Updating of the rainfall field in real-time is accomplished using a distributed parameter Kalman filter to optimally combine measurement information and forecast model estimates. The influence of sampling density on forecast accuracy is evaluated using a series of a simulated rainfall events generated with the same stochastic rainfall model. Sampling was conducted at five different network spatial densities. The results quantify the influence of sampling network density on real-time rainfall field forecasting. Statistical analyses of the rainfall field residuals illustrate improvement in one hour lead time forecasts at higher measurement densities.     

Earthquake Engineering and Engineering Vibration Aims And Scope

正This journal is established by the Institute of Engineering Mechanics(IEM),China Earthquake Administration,to promote scientific exchange between Chinese and foreign scientists and engineers so as to improve the theory and practice of earthquake hazards mitigation,preparedness,and recovery.To accomplish this purpose,the journal aims to attract a balanced number of papers between Chinese and     

Foreword

Destructive earthquakes have caused great damage in China and the United States and collapsing buildings havecaused many deaths and injuries. The field of earthquake engineering studies earthquake hazards, the occurrence ofearthquakes of various magnitudes, the nature of the ground shaking during an earthquake, the vibration of structuresduring earthquakes, the strengthening of existing structures and the design of new structures to be earthquake resistant,and finally, how to cope with earthquake damage and restore a city to normal functioning. Such efforts are in progressin both countries, but unfortunately, the language barrier interferes with the free flow of information between China andthe Untied States. It would be mutually beneficial if some means could be developed to promote the exchangeof information across the Pacific Ocean. This new journal has been established for this purpose and its success willbe an important step in promoting earthquake engineering in China and the United States.     

WORLD ASSOCIATION FOR SEDIMENTATION AND EROSION RESEARCH(WASER)

正President:Giampaolo Di Silvio,Italy Vice Presidents:Ulrich C.E.Zanke,Germany Zhao-yin Wang,China The World Association for Sedimentation and Erosion Research(WASER),inaugurated on Oct.19,2004,is an independent non-governmental,non-profit organization.The mission of WASER is to promote international co-operation on the study     

Enhancing remote sensing research on global change to improve our understanding on Earth system processes

正Global Change includes climate change and other environmental changes caused by the joint interaction among various layers of Earth. From the positive side, global change provides new opportunities to human and other living forms on Earth. In the meantime, it creates tremendous challenges and negative impact. At present, the negative impacts have reached all primary processes of the global ecosystem and every aspect of human society, especially causing degradation of the ecosystem. For instance, intensive deforestation causes decline of biodiversity; global warming causes sea level rise and increases     

Solute concentrations in the lower niger river and the source rock contribution

Water quality analyses for the Niger River for the 1980/81 hydrological year are presented. The samples were collected from the main river at Lokoja, and from two main tributaries, the Kaduna and the Benue Rivers. Different water types were distinguished by the concentrations of major ions. The type Ca > Na > Mg > K - HCO₃ > SO₄ > Cl was represented at all stations during at least part of the year. Chloride was found to dominate the sulphate ion in the Kaduna and Niger, while the Benue maintained a higher concentration of sulphate relative to chloride all year round. Distinct patterns of seasonal variation in the ion concentrations were observed, particularly for the samples collected at Lokoja. Low ion concentrations were prominent during periods of high discharge, while low flow periods coincided with high dissolved ion concentrations. The contribution of rainwater to the total dissolved solids in the river waters was assessed indirectly using rainwater chemistry data from the Gulf of Guinea. The estimated rainwater contribution to the Lower Niger amounts to 5.15 mg 1^?1. Geochemical weathering calculations involving reactions of the four major minerals of granitic rocks - anorthite, biotite, albite, and K-feldspar - with carbon dioxide and water, can account for the average water composition of the Lower Niger. The proportion of the ionic components was also related to the occurrence of the respective element in the minerals.