基于试验测量的高层结构整体抗震损伤评估

结构的损伤模型可以从材料、构件和整体三个层次研究。整体结构损伤模型主要以结构整体为研究对象,从结构的整体反应参数变化研究结构整体性能的变化规律,并对在地震作用下结构的损伤、抗震性能进行分析。结构损伤时物理参数的变化,必将引起动力参数的变化。因此可以通过动力测试来捕捉结构动力参数的变化,如:结构损伤前后固有频率、模态振型和阻尼的变化,可以进行结构损伤诊断。结合在同济大学土木工程防灾国家重点实验室做过的几十个模拟地震振动台试验测试结果,统计和总结地震作用下高层建筑结构自振频率与阻尼比的变化规律,提出了一种新的损伤模型与损伤指标。该损伤模型综合考虑了高阶振型、振型参与系数、结构自振频率、阻尼比等影响因素。最后,用该损伤模型和损伤指标对其中3个典型的高层建筑结构模型模拟地震振动台试验数据进行验证,结果表明:该损伤模型与试验现象基本吻合。可对既有工程结构快速准确地进行动力损伤识别与评估。     

结构损伤动力识别技术的研究与进展

通过对结构损伤的动力识别技术近二十年来国内外研究成果的总结,阐述了结构损伤动力识别研究的发展历程。首先介绍了结构损伤动力识别技术的基本原理,然后从三个方面,即结构损伤的动力识别机理、结构损伤的动力识别参数和结构损伤的识别算法,分别探讨了结构损伤动力识别技术的发展现状和面临的问题,最后对结构损伤动力识别的未来研究趋势进行了展望。     

改进的灰色关联分析法在结构损伤识别中的应用

建议了一种基于改进的灰色关联度进行结构损伤识别的方法。该方法弥补了传统关联度的一些不足,并能较准确、快捷、简便地得到损伤结构的动力响应参数与完好结构对应参数之间的关联度,通过对关联度分析,可以方便地识别结构是否出现损伤,并能定性地给出损伤程度的大小。示例分析表明,利用本文建议方法的计算结果更符合实际。     

基于分形的结构损伤识别方法研究

分形在结构损伤识别中的应用还处于理论研究阶段,还有许多基本问题亟待解决.主要有两个值得深入探讨的问题:如何从理论上证明分形应用于结构损伤识别的合理性、敏感性和噪声鲁棒性;如何在理论分析的基础上研究可行的、有效的大型结构损伤预警参数.总结了目前分形在结构损伤识别中的研究现状,分析了结构动力分频段分形动力特征,提出了广义维数保证准则.最后,展望了分形在结构损伤识别中的应用前景.     

基于动力特性的工程结构损伤识别技术(一)

基于动力特性的损伤识别技术是结构损伤识别的有效方法.介绍了基于动力特性的损伤识别技术研究现状,对基于结构振动响应和系统动态特性参数进行损伤识别的方法和原理进行了评述,提出了结构动力特性的损伤识别技术有待于研究的问题.     

模态应变能法结构损伤检测研究

结合摄动理论，通过分析结构参数修改量高阶项的影响，推导了基于单元模态应变能的结构损伤评估方法；经数值仿真结果表明，其损伤定位准确、程度评估可靠，具有实际应用价值。     

振型平方差法判断结构损伤位置

针对振型是判断建筑物动力特性的主要参数,采用振型平方差法对结构的损伤进行定位,并就结构损伤对频率及振型的影响进行分析,找出结构损伤与动力特性参数间的关系,从而为判断结构损伤位置提供了参考.     

基于BP神经网络的融合参数结构损伤识别研究

1 概述 结构损伤识别及诊断是当前的研究热点。由于动力损伤诊断方法较传统的诊断方法(如目侧及外观检查、无破损或半破损试验、现场载荷试验等)具有较易实施、测试速度快、对结构不造成新的损伤、可在结构的层次上把握整体信息等优点,因而     

谈大跨度结构的损伤识别

综述了常用的几种动力特性损伤识别的方法,并对大跨度结构的损伤识别的研究新进展作了简要的阐述,在此基础之上,对行业界大型工程结构模态参数识别研究进行了展望,并提出指导性建议。     

模态分析的损伤诊断在桅杆结构中的应用

研究了桅杆结构的破坏原因和破坏机理,针对桅杆结构本身的结构动力特性和损伤后的动力特性改变,对应用模态分析方法在桅杆结构的损伤诊断的应用问题进行了分析,指出了模态分析的损伤诊断方法在桅杆结构中的应用方向。     

岩体力学参数取值方法对比研究

岩体材料最重要的特征是具有复杂的变异性,参数值具有显著的不确定性。岩体力学参数的合理取值是岩体力学研究中最困扰研究人员的瓶颈。本文对岩体参数的估计进行了有益讨论,分析了岩体力学参数取值问题多种不同方法的研究状况,这对促进岩体工程设计参数的测定和正确选择很有意义。     

批量计算多区域坐标转换参数的方法研究与实现

测绘地理信息成果常利用坐标转换的方法实现不同成果坐标的转换。利用区域高精度控制点平差成果进行坐标转换残差较小,一般均能通过内符合检查。对于需要对区域内多套控制点成果计算其相互转换关系,采用传统的方法计算过程烦琐,效率低下。本文提出利用坐标转换模型,通过统一坐标成果名称,配置其元数据信息,批量进行坐标转换参数计算的方法,大大提高了多套控制点成果坐标参数计算的效率。     

Identification of understrength and overstress parameters for RC buildings in Greece

The need for a simple, rational and instructive model of seismic capacity evaluation of existing buildings is stressed and the advantages of using understrength and overstress coefficients are illustrated.Identification and classification of understrength and overstress parameters of earthquake behaviour of RC buildings in Greece is presented, based on extensive surveys after the Volvi (1978), Magnissia (1980) and Alkyonides (1981) earthquakes. These parameters apply equally to RC buildings in other geographical areas. Distribution of frequencies for the different types and degrees of understrength and overstress problems in Greek RC buildings is also given.Tentative detailed criteria for the assessment of λ coefficients and weighting factors are developed. Based on ø and λ coefficients and on weighting factors, the general form of a self-contained model for seismic capacity evaluation of low to medium rise RC buildings is developed, which supplements the already existing models for the case of simplified modelling.It is concluded that, although a new self-contained model has been developed, more research is needed for reliable assessment of seismic capacity of RC buildings.     

导航型手持GPS接收机各参数的求解方法

文章主要介绍导航型手持GPS在运用过程中如何确定相关参数,并通过实例介绍帮助相关专业人员在不同区域工作时如何正确计算当地导航型手持GPS各参数,以达到正确使用的目的。     

Comparison of the microbiological and chemical characterization of harvested rainwater and reservoir water as alternative water resources

Rainwater harvesting (RWH) offers considerable potential as an alternative water supply. In this study, all of the harvested rainwater samples met the requirements for grey water but not for drinking water. In terms of microbiological parameters, total coliform (TC) and Escherichia coli (EC) were measured in 91.6% and 72%, respectively, of harvested rainwater samples at levels exceeding the guidelines for drinking water, consistent with rainfall events. In the case of the reservoir water samples, TC and EC were detected in 94.4% and 85.2%, respectively, of the samples at levels exceeding the guidelines for drinking water. Both indicators gradually increased in summer and fall. The highest median values of both TC and EC were detected during the fall. Chemical parameters such as common anions and major cations as well as metal ions in harvested rainwater were within the acceptable ranges for drinking water. By contrast, Al shows a notable increase to over 200 μg L^− 1 in the spring due to the intense periodic dust storms that can pass over the Gobi Desert in northern China. In terms of statistical analysis, the harvested rainwater quality showed that TC and EC exhibit high positive correlations with NO₃⁻ (ρ_TC = 0.786 and ρ_EC = 0.42) and PO₄⁻ (ρ_TC = 0.646 and ρ_EC = 0.653), which originally derive from catchment contamination, but strong negative correlations with Cl⁻ (ρ_TC = − 0.688 and ρ_EC = − 0.484) and Na⁺ (ρ_TC = − 0.469 and ρ_EC = − 0.418), which originate from seawater.     

Microbiological and chemical properties of litter from different chicken types and production systems

Chicken litter is produced in large quantities from all types of poultry raising activities. It is primarily used for land application, thus it is essential to analyze its properties before it is released to the environment. The objective of this study is to compare the microbiological and chemical properties of litter generated from layer and broiler chickens reared under intensive and free-range production systems. The microbiological analysis consisted of the enumeration of total bacteria, total coliforms, Staphylococcus species, Salmonella species and Clostridium perfringens. Chicken litter from layers reared under intensive and free range systems showed lower mean total bacterial count than the litter collected from chicken broilers reared under either of the two systems (P=0.0291). The litter from intensive layers had the lowest mean total coliform counts (P=0.0222) while the lowest Staphylococcus species count was observed in the litter from free-range layers (P=0.0077). The C. perfringens count was the lowest in chicken litter from intensively raised broilers and layers (P=0.0001). The chemical properties of litter from the different chicken types and production systems were compared based on determination of pH, electrical conductivity, carbon, nitrogen, phosphorus, potassium, cadmium and zinc. Litter from free-range broilers showed the highest pH value (P=0.0005); however, the electrical conductivity was higher in the litter from both intensive and free-range layers compared to the litter from both broiler production systems (P=0.0117). Chicken litter from intensive systems had higher nitrogen content than litter from free-range systems (P=0.0000). The total phosphorus was the lowest in free-range broiler litter (P=0.0001), while the total potassium was the lowest in litter from intensively managed broilers (P=0.0000). Zinc appeared higher in litter from layers compared to that from broilers (P=0.0101). The cadmium content was higher in the litter from free-range broilers and layers compared to that in the litter from intensively managed systems (P=0.0439). Staphylococcus species in the litter as well as cadmium concentrations seem to be the most critical parameters presenting risks on the environment and on human health. Based on the lowest coliform counts (an indication of water pollution), the high nutrient levels and the low cadmium values, litter from intensively managed layers appears as the most suitable for application on agricultural soils.     

给水厂高密度沉淀池沉淀效果三维数值模拟与优化

应用FLUENT流体力学软件对重庆某大型在建给水厂高密度沉淀池沉淀区的流速场和浓度场进行了三维数值模拟,分析了不同运行参数与结构参数对沉淀区水流流场与沉淀效果的影响。模拟结果表明,增加进水口流速在一定程度上缓解了异重流现象,但不能提高沉淀效果;选取进水口流速为0.016 m/s,将沉淀池的导流墙左侧改为弧形,在斜板沉淀区前端加上1 m的挡板,可使异重流现象减弱,且沉淀效果得到明显的改善。     

基于Hoek-Brown准则的山岭隧道围岩力学参数估计

将围岩岩体分级系统(Q系统)引入到Hoek-Brown强度准则中,引入节理粗糙度、节理充填物的抗剪强度及岩石所受应力3个指标,对地质强度指标(GSI)进行定量化修正,并基于围岩基本质量指标BQ、裂隙组数、围岩节理条件以及Q系统评分值,重新构建一种GSI的定量化分析方法,通过测量扰动前后围岩的纵波波速优化岩体的扰动参数D。基于修正后的Hoek-Brown强度准则与Mohr-Coulomb强度准则进行等效转化,估算岩体的力学参数,通过与实例工程中试验结果进行对比,得知此方法是合理、可行的。     

关于后置发动机式沥青洒布车几个重要技术参数的确定

本分析和讨论后置发动机式沥青洒布车的动力、沥青泵的匹配以及洒布精度、喷洒压力、洒布量等有关重要技术参数的确定，以期对设计和使用提供帮助。     

Mechanical properties and behaviour of soils under the triaxial test,the Yamauchi landslide,Japan

A series of consolidated undrained triaxial tests have been undertaken on material from the Yamauchi landslide in northern Kyushu. The samples were obtained from two specially drilled boreholes. Both the logging and the geotechnical test results indicate a wide variation which is probably attributable to the differing degree of weathering/hydrothermal alternation. Two types of stress strain and pore-water pressure responses were observed during the test. Two failure modes were identified – plastic and semiplastic. Electronic Publication