龙厦铁路石桥头隧道地表建筑物变形监测方法及计算分析     

封良泉  赵建三  时林军 《北京测绘》2009,(4):50-52

石桥头隧道横跨龙岩市区,隧道长、埋深浅、岩质差、地表建筑物密集。在隧道开挖初期,建筑物出现较大沉降、倾斜、拉裂和错裂,严重影响建筑物正常使用,危及居民安全。为此对建筑物进行了沉降监测、水平变形监测和倾斜监测,并计算建筑物的曲率,取得很好的效果,且对隧道施工起到很好的指导作用,本文简要的研究了其监测方法及计算分析。  相似文献   

Curvature of Flexibility Matrix for Damage Identification in Legs of Jacket Platforms     

陈立  马骏  赵德有  邬君 《中国海洋工程》2008,22(4):547-559

In this paper a new nondestructive damage identification method is introduced. The method based on flexibility matrix can be used to detect and locate structm＇al damage and evaluate the severity of damage in legs of jacket platforms by modal parameters of a structure. With the modal data for only the few lower modes in both the intact and damaged states, the one-dimensional and two-dimensional distributed curvatures can be used to analyze damage location and the severity. Instead of directly comparing the curvatures before and ＇after damage, the method here uses modal parameters only in the damaged structure to detect the damage and it consists of three parts. First, ilexibility matrix is obtained by use of the absolute maximum in each column. Second, because the legs of jacket platforms are the pipe-like structure, the circumferential flexibility curvature matrix is obtained by use of the circular curvature. At last, equivalent curvature ratio is defined and the curve meaning equivalent curvature ratio and the severity of damage relationship for one element is given through the data of damage severity from ten percent to ninety percent by numerical simulation. Many existing damage detection methods need two steps, locate the damage firstly and evaluate the severity of the damage. However, the method present- ed! in this paper can locate and then evaluate the severity of damage at the same time. The numerical analysis results in- dicate that the present method is effective, useful and only need the first and the second mode data of the structure.  相似文献   

基于模态曲率法的大跨度斜拉桥损伤识别   总被引：2，自引：0，他引：2  

李忠献  齐怀展  朱劲松 《地震工程与工程振动》2007,27(4):122-126

大跨度斜拉桥是重要的交通结构,研究其在主梁损伤条件下的损伤定位问题具有重要的工程价值。合理选择设计参数并对其进行敏感性分析,根据现场实测的桥梁动力特性数据,通过调整选定的设计参数对初始的有限元模型进行修正。在基准有限元模型的基础上,通过模拟不同位置和不同程度的主梁损伤,探讨了模态曲率法对结构损伤识别的有效性。结果表明,模态曲率法能够对大跨斜拉桥进行初步的损伤定位,确定主梁单处损伤和多处损伤的损伤位置;对于单处损伤,在噪声水平3%的情况下仍具有较好的适用性。从而为后期更为精确的桥梁结构损伤检测提供依据。  相似文献   

解平面质点问题之方法的新探讨     

林中和  梁德余 《广东海洋大学学报》1991,(1)

本文使三种平面坐标按一个固定关系互相配合,得到与此对应的一系列公式,为解大量的平面质点问题提供简便方法。  相似文献   

Hydrochemical framework of groundwater in the Ankobra Basin,Ghana   总被引：4，自引：0，他引：4  

Benony K. Kortatsi 《Aquatic Geochemistry》2007,13(1):41-74

Hydrochemical and stable isotope (¹⁸O and ²H) analyses of groundwater samples were used to establish the hydrochemistry of groundwater in the Ankobra Basin. The groundwater was generally mildly acidic, low in conductivity and undersaturated with respect to carbonate phases. Major ions except bicarbonate were low and dissolved silica was moderately high. Silicate minerals weathering is probably the main process through which major ions enter the groundwater. Groundwater samples clustered tightly along the Global Meteoric Water Line suggesting integrative, smooth and rapid recharge from meteoric origin. The majority of the boreholes and a few hand dug wells cluster towards the Ca–Mg–HCO₃ dominant section of the phase diagram, in conformity with the active recharge and short residence time shown by the isotope data. Aluminium, arsenic, manganese, iron and mercury were the only trace metals analysed with concentrations significantly above their respective detection limits. Approximately 20%, 5%, 40% and 25% respectively of boreholes had aluminium, arsenic, iron and manganese concentrations exceeding the respective WHO maximum acceptable limits for drinking water. The relatively large percentage of boreholes with high concentration of aluminium reflects the acidic nature of the groundwater.  相似文献   

Improving a digital elevation model by reducing source data errors and optimising interpolation algorithm parameters: An example in the Loess Plateau,China   总被引：1，自引：0，他引：1  

《International Journal of Applied Earth Observation and Geoinformation》2007,9(3):235-246

A hydrologically correct digital elevation model (DEM) forms a basis for realistic environmental modelling, especially in complex terrain. We have performed a study in the Coarse Sandy Hilly Catchments (CSHC) of the Loess Plateau, China, which demonstrates pragmatic, yet effective methods for improving the quality of the DEM by: (1) identifying and correcting source topographic data errors and (2) optimising ANUDEM algorithm parameters. Improvement in the DEM based on fixing over 1100 errors in the input topographic data, and optimising key ANUDEM parameters was assessed using higher accuracy independent validation of 32 contributing areas and 1474 spot heights, and by semi-quantitative analysis of DEM derivatives produced from ANUDEM and Triangular Irregular Network (TIN) algorithms. Improvement in the ANUDEM DEM over the original TIN DEM was shown where the percentage of the total absolute difference in contributing areas reduced from 10.43 to 3.51%, and the bias between the spot heights and DEM elevations reduced from 45 to 32 m. Large improvement in DEM quality was gained by using ANUDEM instead of TIN, with smaller improvement gained by fixing source data errors, and optimising ANUDEM parameters.  相似文献   

基于小波分析的线状要素压缩优化的综合性研究     

王玉海  朱长青 《武汉大学学报(信息科学版)》2007,32(7):630-632,653

利用小波分析理论、Douglas算法、曲率分析算法，对线状要素的压缩优化进行了深入的研究，并在建立线状要素压缩优化的自适应模型的基础上，对实际数据进行了试验。结果表明，此方法不仅能够保持高的压缩比，而且能够很好地保持原数据的特征。  相似文献   

Modeling and Simulation of Supercavity with Inertial Force in the Horizontal Curvilinear Motion简     

邹望  于开平  张广 《中国海洋工程》2014,28(1):31-42

To make a curvilinear motion in the horizontal plane is one of the most contents for realizing the maneuverability of the supercavitating vehicle. It is significant to achieve the controllability and maneuverability of the vehicle in three dimensions both theoretically and practically on research. Models of angle of attack, gravity and inertial force effects on the supercavity in the horizontal curvilinear motion are established, respectively. The supercavity is simulated based on these models in combination with Logvinovich model and the unsteady gas-leakage rate model at the given ventilation rate, and the effect of the inertial force on it is analyzed numerically. Results show that the maximum deviation of the center line of the cross section of supercavity towards the outward normal direction of its trajectory increases as the cavitation number or curvature radius decrease and always occur in the tail because of the increase of inertial effects along the axis of supercavity from the cavitator when other models and flow parameters are constant for the given trajectory curvature. For the variable curvature, the supercavity sheds due to its instability caused by the time-varying angle of attack. The deviation increases along the length of supercavity if the curvature remains the same sign.  相似文献   

A comparative study of the ATC-40 recommended and numerically derived M-(ψ) relationship     

Sifat Sharmeen Muin  Tahsin Reza Hossain 《地震工程与工程振动(英文版)》2011,10(4)

Nonlinear static analysis procedures are key tools in evaluating the performance of existing buildings and verifying the design of seismic retrofits in seismically active regions.In this procedure,nonlinear force-displacement or moment-curvature (M-(4)) behavior needs to be defined.In the ATC-40 document,values of M-~ have been proposed to model elements in a nonlinear procedure.However,these values need to be investigated to determine if they are representative of actual values.In this paper,an attempt has been made to numerically derive M-（4） curves to simulate actual performance.Then,these curves are compared with the ATC-40 recommended curves with respect to various parameters.The study indicated that ATC-40 suggested values are conservative in nature in most situations.  相似文献   

山坡地形曲率分布特征及其水文效应分析——真实流域的野外实验及相关分析研究   总被引：2，自引：0，他引：2       下载免费PDF全文

刘金涛  冯德锃  陈喜  吴吉春  顾卫明 《水科学进展》2011,22(1):1-6

研究了山坡地形曲率的空间分布特征,发现流域略呈现出微凹、发散的形状特征,平均的剖面和水平曲率分别为-4.62×10-4和3.49×10-4。通过划分源头型和边坡型山坡,发现源头山坡多是收敛的,边坡型山坡则多为发散的;在山坡内部收敛、发散、凹和凸等地形地貌类型是同时存在的,即山坡一般由相互组合的各种坡型所组成。基于野外采样观测的成果,分析了和睦桥子流域90个采样点的土壤含水量及其对应曲率的相互关系。结果显示:一般来说,凹形山坡、收敛形山坡对应的土壤含水量更高,而凸形和发散形山坡对应的土壤含水量较低;不论是收敛的凹坡,还是发散的凸坡,其采样点土壤含水量都有随高程下降而升高的趋势,即愈靠近沟谷土壤含水量愈大。  相似文献