不同阻尼特性材料组合结构的弹塑性动力时程响应计算

本文提出一种不必形成与存储总阻尼矩阵的非线性结构动力时程分析的算法,用于计算非比例、非经典阻尼结构弹塑性动力响应。该算法的软件实现简单,对现有比例阻尼结构分析程序稍加修改即可。基于此算法的计算机程序满足了由两种阻尼特性材料建造的建筑结构非线性动力时程分析的需要。     

MCS自适应算法在非线性结构AMD控制中的应用

控制算法决定着振动控制的稳定性和减振效果,是结构AMD主动控制的核心组成部分。将最小控制综合(MCS)自适应算法运用于AMD控制结构系统,该算法不要求事先知道受控结构的精确力学模型和参数,且在受控结构进入非线性状态下也能达到很好的控制效果。利用拉格朗日方程推导了采用MCS算法的非线性结构AMD系统的控制方程;在小型振动台上对刚度突变结构进行了控制试验。试验结果表明:采用MCS自适应算法的AMD系统可以有效地减小刚度突变结构响应,并且可让实际结构响应与参考模型预期响应保持一致,达到满意的减振效果。     

基于有限测点模态信息的结构物理参数识别

研究了测试信息不完备情况下的结构参数识别问题,针对稀疏模态的结构系统,提出了基于有限测点模态信息的优化识别算法。该算法通过有限测点上的模态参数构造关于结构物理参数的目标函数,然后采用遗传算法进行参数识别。最后一数值算例说明了该算法的可行性。     

基于改进广义卡尔曼滤波的结构损伤识别方法

针对传统的广义卡尔曼滤波算法不能有效地追踪结构刚度的变化情况,本文以传统卡尔曼滤波理论为基础,得到了基于衰减记忆的广义卡尔曼滤波算法公式,利用该算法对所得到的地震响应信号进行分析,提取结构的特性,辨识结构的参数,并从中判断结构损伤发生的时刻、位置及程度,改善了广义卡尔曼滤波的效果。衰减记忆的广义卡尔曼滤波算法只能够判断出结构参数变化的时间并且容易出现振荡,因此采用了一种新的自适应追踪技术,用一个自适应因子矩阵代替了原有的遗忘因子,这种技术可以有效追踪结构参数变化的时间、位置和大小,从而能够在线识别出结构的损伤。     

环境激励下一种基于免疫机制的结构损伤诊断方法

结构状况发生改变时,结构的振动特性将发生变化。免疫算法能有效检测出振动特性的变化。本文将环境激励下的结构响应重构相空间,对其进行奇异值分解后,选择适当个数的奇异值构造特征参数集合,应用反向选择算法进行异常值检测,以ASCE学会提出的基准结构为对象进行研究,讨论了不同个数的特征参数对检测结果的影响。分析表明,该算法能有效地判断结构状况的变化。     

基于模拟植物生长算法的桁架结构截面与形状优化分析

针对桁架结构优化问题，给出基于改进的生长空间限定与并行搜索的模拟植物生长算法（GSL&PS-PGSA）优化模型，对典型平面桁架、空间桁架结构分别进行截面优化及形状优化分析，结果表明：改进GSL&PS-PGSA算法的优化效果显著，其优化所得结构经济高效；对于平面桁架截面优化，相比二级优化法、相对差商法及连续变量法，改进GSL&PS-PGSA所得结构较其减少了8%～15%的用钢量；对于空间桁架优化，截面优化所得结构总质量较序列两级算法轻约8.1%，较蚁群算法轻约3.6%，而形状优化所得结构总质量则分别较序列两级算法、蚁群算法轻约31.2%、22.4%。因此，改进的GSL&PS-PGSA算法对桁架结构优化问题具有良好的适用性。     

结构非弹性动力响应的力模拟法

提出了基于力模拟法研究受动力荷载作用的结构非线性特性的一种新的算法，与传统改变刚度矩阵的方法不同，该算法是通过改变结构位移场来进行非弹性分析。结构的每一个非弹性变形代表一个自由度，因而结构所有的非弹性特性可通过一个方程表示。这个算法在计算时间上是非常有效的，因为它仅需使用初始刚度矩阵，且当运动动力分析中的状态空间数值积分法时，可以达到很高的数值精度。而且，这个算法在分析结构应变硬化性质、弹塑性性质和应变软化性质时都是稳定的。通过将这种算法与已有的非弹性动力分析软件程序相比较，说明了这个算法是的、高效的。最后，通过对一个6层医院建筑动力响应分析的应用，演示了该算法在分析实际结构中的完整的非弹性分析过程。     

生命线工程系统抗震可靠度算法复杂性及简化原则

研究了生命线工程系统抗震可靠度常规算法的适用性，定义了算法的时间复杂性和结构复杂性，分析了使可行算法失效的原因，给出了回路分解公式，提出了优先降低结构复杂性的简化原则。     

地震下结构振动的最优控制算法模型比较与改进

模拟地震激励输入结构的过程,将控制目标函数化解到每个时间步长上。用激励所产生的脉冲响应重新构造控制目标函数,直接从泛函变分出发,推导出了一种改进的最优控制算法,并用状态转移的数值方法加以实现。从概念上讲,本算法是一种更为合理的结构最优控制算法。算例表明,在相同控制能量下,本算法能更有效地削减响应峰值,且稳定性良好。     

地震动作用下的结构瞬时开闭环最优控制算法

本文提出了瞬时开闭环最优控制算法，这是建立在时程分析基础上的最优控制算法，不需要实施结构的模态解耦，适合于地震动作用下非线性结构的控制分析，这种算法不仅可以区分开环，闭环和开闭环控制的不同效果，而且结构的位移，速度和加速度响应都能有效地得到控制。     

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     

Dissolved Carbohydrate Concentration,Composition, and Bioavailability to Microbial Heterotrophs in Stream Water

Dissolved total carbohydrates (DTCH), dissolved free monosaccharides (DFMS), dissolved organic carbon (DOC), biodegradable DOC (BDOC), and humic substances (HS) were measured in White Clay Creek (WCC), a stream in southeastern Pennsylvania Piedmont, USA. Samples were collected over different seasons and under baseflow and stormflow conditions. DOC concentrations ranged from 1.0 to 12.8 mg/L C with the highest concentrations associated with stormflows. Carbohydrates ranged from 0.42 to 12.4 μM and accounted for 2.9 to 12.7% of the DOC. Humic substances represented the major DOC fraction, accounting for 55 to 72% of the DOC pool under all flow conditions. The humic fraction had a lower carbohydrate content (4.4%) than the non-humic fraction of DOC (7.2%). Stormflow DOC was enriched in carbohydrates relative to baseflow DOC, but the percentage of humic-C changed little. Carbohydrates were primarily present as dissolved polysaccharides (55%), but a significant fraction was bound to humic substances (40%), while a small proportion was present as monosaccharides (5%). The major monosaccharides in stream water, listed in order of decreasing concentration, included glucose, galactose, rhamnose, xylose, arabinose, mannose, and fucose. On average (30.6 ± 7.4)% (n = 44) of the stream water DOC was biodegradable, and carbohydrates accounted for 9.9 to 17.7% of the BDOC.