钢筋混凝土框架柱震损程度量化鉴定方法          下载免费PDF全文

曲博闻  张昊宇  毛晨曦  张亮泉 《世界地震工程》2018,34(3):085-93

钢筋混凝土结构震后损伤鉴定中,最常见的方式是鉴定者观察房屋破坏现象,根据经验给出震损等级。该方法直观高效,但对鉴定者的专业经验要求较高,且鉴定结果的主观差异较大。对此以RC框架柱为对象,开展了基于震损现象的震损量化鉴定方法研究:在RC框架柱震损现象量化试验基础上给出基于构件骨架曲线特征阶段的震损分级方法;对7个RC框架柱试件进行了改进Park-Ang损伤指数分析,建立了RC框架柱损伤指数-震损分级-震损现象的对应关系;基于RC框架柱的试验结果及典型震害编制了RC框架柱震损图集,并给出了使用图集进行框架柱震损鉴定的流程及方法。使用该方法对2个实际震害中的RC框架柱进行了震损鉴定,可为更加客观以及准确地开展钢筋混凝土结构的震损鉴定提供参考。  相似文献   

西辽河流域鱼类生物完整性指数评价及与环境因子的关系   总被引：3，自引：1，他引：2  

张浩  丁森  张远  贾晓波  孟伟  郭彪 《湖泊科学》2015,27(5):829-839

采用鱼类生物完整性指数(F-IBI)评估西辽河流域环境质量,利用相关分析筛选了影响F-IBI的环境因子,结合局部加权回归散点修匀法(LOWESS)估算了这些环境因子的保护限值.结果表明:20个候选参数指标中,鳅科鱼类物种百分比、底层鱼类物种数、耐受性鱼类个体数、杂食性鱼类物种数和筑巢产卵鱼类个体百分比适合作为西辽河流域F-IBI构建参数.采用比值法统一参数量纲,以参考点F-IBI值的95%分位数作为健康参考值,对全流域44个采样点进行健康评价,得到健康点位5个(11.4%),亚健康点位9个(20.5%),一般点位12个(27.3%),差点位11个(25.0%),极差点位7个(15.9%).电导率、氨氮浓度、碱度和泥沙比例与F-IBI呈显著负相关,坡降和草地比例与F-IBI呈显著正相关.经LOWESS和独立样本t检验发现,电导率、氨氮浓度、碱度、泥沙比例和草地比例等环境因子的保护限值分别为531μS/cm、0.55 mg/L、4.4 mmol/L、47.2%和37.0%,且限值两侧的F-IBI分值差异显著,该结果可作为西辽河流域环境管理中鱼类群落完整性保护的有益参考.  相似文献   

Changes in reference evapotranspiration over China during 1960–2012: Attributions and relationships with atmospheric circulation          下载免费PDF全文

Rongfan Chai  Shanlei Sun  Haishan Chen  Shujia Zhou 《水文研究》2018,32(19):3032-3048

This study investigates reference evapotranspiration (ET₀) trends in China from 1960 to 2012 based on the Penman–Monteith equation and gridded meteorological measurements. Under the combined impacts of factors influencing ET₀ (i.e., net radiation [RN], mean temperature [TAVE], vapour pressure deficit [VPD], and wind speed [WND]), both seasonal and annual ET₀ for the whole China and more than half of the grids decreased over the past 53 years. The attribution analyses suggest that for the whole China, the WND is responsible for annual and seasonal ET₀ decreases (excluding summer, where RN is responsible). Across China, the annual cause of WND with the largest spatial extent (43.1% of grids) mainly derives from north of the Changjiang River Basin (CJRB), whereas VPD (RN) as a cause is dispersedly distributed (within and to the south of the CJRB). In summer, RN is dominant in more than half of the grids, but the dominance of VPD and WND accounts for approximately 90% of grids during the remaining seasons. Finally, the correlation coefficients between ET₀ and the Atlantic Oscillation (AO), North AO, Indian Ocean Dipole (IOD), Pacific Decadal Oscillation (PDO), and El Niño Southern Oscillation (ENSO) indices with different lead times are calculated. For the whole China, annual and seasonal ET₀ always significantly correlate with these indices (excluding the IOD) but with varied lead times. Additionally, near half of the grids show significant and maximum (i.e., the largest one between ET₀ and a certain index with a lead time of 0–3 seasons) correlation coefficients of ET₀ with PDO in spring and summer, ENSO in autumn, and AO in winter. This study is not only significant for understanding ET₀ changes, but it also provides preliminary and fundamental reference information for ET₀ prediction.  相似文献   

应用底栖动物完整性指数评价太湖生态健康   总被引：16，自引：4，他引：12  

蔡琨  张杰  徐兆安  吴东浩  张咏  王备新 《湖泊科学》2014,26(1):74-82

依据2010年春季至2012年秋季,太湖32个样点的底栖动物和环境变量共11次的季节性调查结果,采用干扰程度最小系统法定义构建底栖动物生物完整性指数的参照系统,提出了确定参照系统的4个基本条件,进而按非湖心区和湖心区两个生态区分别构建太湖底栖动物完整性指数(LTB-IBI).通过对候选生物参数的分布范围筛选、判别能力分析、与理化因子的相关性和参数间的冗余分析,获得了非湖心区LTB-IBI的4个构成指数:总分类单元数、Simpson多样性指数、前3位优势单元%和BMWP指数,以及湖心区LTB-IBI的5个构成指数:总分类单元数、Simpson多样性指数、甲壳+软体分类单元数、前3位优势单元%和BMWP指数.采用比值法统一构成指数量纲,分别构建了非湖心区和湖心区LTBIBI指数,评价太湖水生态健康的等级.2010-2012年,太湖生态健康总体上呈现逐步提升的趋势.影响太湖底栖动物完整性的重要环境变量是水体中的氮含量.研究表明,连续观察数据可较大程度上提高太湖LTB-IBI指数的可靠性和评价结果的合理性.  相似文献   

地磁活动K指数自动计算FMI方法的改进   总被引：1，自引：1，他引：0       下载免费PDF全文

王建军  李琪  杨冬梅  陆镜辉 《地球物理学报》2017,60(7):2534-2544

将Kp指数与国际地磁学与高空物理学协会(International Association of Geomagnetism and Aeronomy,下文简称IAGA)推荐的FMI方法(V1.0)计算的K值对比分析后发现,二者的差值在中国区域内出现"不同台站之间K1~K8两头离散、K值整体高出K_p约0.5个单位、个别日期S_R计算错误、相邻日期S_R频繁出现跨天台阶"现象.针对这些现象,分析了可能产生的原因,并对原FMI算法进行了四处改进.用改进后的FMI算法计算了全球8个台站、中国5个台站在2003-2005年和2009年共4年的K指数数据,并将计算结果分别与Kp指数以及这些台站用其他方法计算的K值进行一致性比较,发现改进后的计算结果与二者更为接近,说明本文对FMI方法的改进是有效的.  相似文献   

Dunefield Activity and Interactions with Climatic Variability in the Southwest Kalahari Desert     

J. E. Bullard  D. S. G. Thomas  I. Livingstone  G. S. F. Wiggs 《地球表面变化过程与地形》1997,22(2):165-174

An analysis is undertaken of the temporal variability of climatic parameters that influence dunefield aeolian activity. Data from seven meteorological stations in the southwestern Kalahari Desert are used, spanning the period 1960–1992. Erosivity is considered through analysis of wind data, and erodibility through analysis of precipitation and potential evapotranspiration, which together influence dune surface plant growth. The data are integrated using Lancaster's ‘mobility’ index which provides a measure of potential dune surface sand transport. This is renamed ‘potential dune surface activity index’, to reflect the actual characteristic that is measured. The subsequent analysis indicates that dunefield activity is episodic and temporally variable, that both erosivity and erodibility vary through time, and that present levels of activity cannot be characterized by a single simple state. © 1997 by John Wiley & Sons, Ltd.  相似文献   

Effects of grain size distribution on mineralogical and chemical compositions: a case study from size‐fractional sediments of the Huanghe (Yellow River) and Changjiang (Yangtze River)     

Xiaojing Zhou  Anchun Li  Fuqing Jiang  Jian Lu 《Geological Journal》2015,50(4):414-433

The influence of hydrodynamics on the chemical composition of sediments is based on the uneven distribution of element abundances in different size fractions. In this study, 72 size‐fractional sediments from the Huanghe (Yellow River) and Changjiang (Yangtze River) riverbeds were measured with XRD, SEM, ICP‐AES and ICP‐MS. The analysis results show that the mineral and chemical characteristics change with grain size in the Huanghe and Changjiang sediments. According to the principal components analysis, three independent geochemical factors were found. The first factor elements, Zr, Hf, Th, U, Y, La and TiO₂ are influenced by the existence of heavy minerals. The second factor elements, Al₂O₃, alkalis, alkaline earth (excluding Ca and Sr) and most of the transitional metals are dominated by clay minerals. The third factor group includes Ca and Sr, which were controlled by calcium‐bearing mineral contents and chemical weathering intensities. The various grain size distributions greatly affect the mineralogical and chemical compositions of bulk sediments. Compared to other size fractions, the 5–6PHI size fractions of the Huanghe and Changjiang sediments have special mineralogical and chemical compositions, and intermediate volume percentages. Weight or volume percentage of each size fraction may be more suitable than mean grain‐size of the bulk sediment to elucidate the grain size effects. Chemical Index of Alteration (CIA) values increase steeply with decreasing grain size, while Weathering Index of Parker (WIP) values are relatively stable. Because of the big influence of the abundance of clay minerals on CIA values, it is questionable to use CIA as a proxy of weathering intensity. Considering the clay mineral effects, stability in values and heterogeneous material properties, WIP has the potential to indicate the chemical weathering intensity of sediments. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献