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101.
Zhao-Dong Xu Ya-Peng Shen Hong-Tie Zhao 《Soil Dynamics and Earthquake Engineering》2003,23(8):683-689
The paper introduces a synthetic optimization analysis method of structures with viscoelastic (VE) dampers, namely the simplex method. The optimal parameters and location of VE dampers can be determined by this method. Numerical example and a shaking table test about reinforced concrete structures with VE dampers show that the seismic responses of structures will be reduced more effectively when the parameters and location of VE dampers are designed in accordance with the results calculated by the simplex method. 相似文献
102.
In this research, a reliable Cone Penetration Test data set was gathered with a wide range of parameters. This data was incorporated in a Neural-Networks computer software called STATISTICA Neural-Networks. The back propagation algorithm with a multilayer perceptron network is utilized to analyze the liquefaction occurrence in different sites. In this study, different sets of effective parameters for the neural-network analyses are selected such that to reduce the noise and to obtain more accurate results.Considering the relative importance of effective parameters in liquefaction assessment, it is indicated that σ0, σ′0 together play a more important role than what previously was assumed and hence the relative importance of the qc and seismic parameters are decreased compared with the previous works. The results presented here have more accuracy than previous works while at the same time, the range of the parameters used in this study is much wider than what was previously used. This range of parameters makes the proposed method applicable for practical purposes. 相似文献
103.
104.
During the past three decades, damage due to swelling action of Ankara Clay has been observed more clearly in some parts of Ankara where rapid expansion of the city led to the construction of various kinds of structures. In this study, a comprehensive research program has been conducted (i) to investigate the effect of remoulding and desiccation on the swelling behavior of Ankara Clay and its swelling anisotropy, (ii) to estimate depth of active zone, (iii) to develop a simple technique in determining the magnitude of swelling based on water content of the soaked specimen after 24 and 72 h (wmax24,72), and (iv) to produce predictive models which could be used to estimate the swelling potential of Ankara Clay from its mineralogical and simply measured engineering characteristics. A laboratory testing program was carried out using both undisturbed, and remoulded and desiccated samples selected from 20 different locations. Montmorillonite was identified as being the main clay mineral present. Based on the moisture content variation with depth, the active expansive zone was considered to be about 2 m. The test results suggest that swelling pressure of the clay considerably decreases and/or dies out when the water content is greater than 30%. It is also noted that the measured lateral swelling is significantly in excess of the vertical equivalent indicating an anisotropy with respect to swelling. Statistical assessments indicate that a new parameter (wmax24,72) from a simple test, suggested in this study, is a very strong parameter for predicting swelling parameters of Ankara Clay. Based on 60 empirical predictive equations with coefficients of correlation between 0.96 and 0.66 from multiple regression analyses, wmax24,72, methylene blue value, liquid limit, dry unit weight and smectite content are the most important index and mineralogical properties to predict the swelling parameters of Ankara clay with small deviations from the measured values. 相似文献
105.
Recent Precipitation Trends in Hungary in the Context of Larger Scale Climatic Changes 总被引:1,自引:0,他引:1
The time series of monthly precipitation totals from 14 Hungarian observing stations (1901–1998) were analysed to reveal the long term changes in precipitation characteristics occurred in the 20th century. A particular attention was given to the changes in the recent decades and their links with the larger scale climatic and circulation changes over Europe and the Atlantic.The statistical significancesof systematic changes are controlled by linear trend analysis and the Mann–Kendall test. The long term fluctuations are illustrated applying a 15-point Gaussian filter on the time series. The Standardised Precipitation Index is used to evaluate the changes in the drought event frequency. The relationships with larger scale changes are mostly discussed relying on contemporary papers, and the Grosswetterlagen Catalogue is used as well.The annual precipitation total decreased by 15–20% in Hungary during the 20th century. The decline is substantial in both halves of the century, but the precipitation sums in the transition seasons declined in the first 50 years, and the winter precipitation decreased in the latest decades. The precipitation total of the period November–February declined significantly in the last 50 years. In the same time the mean winter value of the North Atlantic Oscillation Index (NAOI) increased, the positions of the main pressure patterns over the Atlantic are shifted northeastward, and lot of other coherent changes detected in the winter climate of the European–Atlantic region. The mean summer precipitation total has hardly changed, but the frequency of summer drought events increased. There are some signs of a shift of the Hungarian summer climate towards a Mediterranean like climate. 相似文献
106.
Daniel G. Gavin W. Wyatt Oswald Eugene R. Wahl John W. Williams 《Quaternary Research》2003,60(3):356-367
The modern analog technique typically uses a distance metric to determine the dissimilarity between fossil and modern biological assemblages. Despite this quantitative approach, interpretation of distance metrics is usually qualitative and rules for selection of analogs tend to be ad hoc. We present a statistical tool, the receiver operating characteristic (ROC) curve, which provides a framework for identifying analogs from distance metrics. If modern assemblages are placed into groups (e.g., biomes), this method can (1) evaluate the ability of different distance metrics to distinguish among groups, (2) objectively identify thresholds of the distance metric for determining analogs, and (3) compute a likelihood ratio and a Bayesian probability that a modern group is an analog for an unknown (fossil) assemblage. Applied to a set of 1689 modern pollen assemblages from eastern North America classified into eight biomes, ROC analysis confirmed that the squared-chord distance (SCD) outperforms most other distance metrics. The optimal threshold increased when more dissimilar biomes were compared. The probability of an analog vs no-analog result (a likelihood ratio) increased sharply when SCD decreased below the optimal threshold, indicating a nonlinear relationship between SCD and the probability of analog. Probabilities of analog computed for a postglacial pollen record at Tannersville Bog (Pennsylvania, USA) identified transitions between biomes and periods of no analog. 相似文献
107.
108.
109.
岩体工程质量分级应用研究 总被引:1,自引:0,他引:1
岩体质量评价采用的测试技术包括地质勘察、弹性波检测和室内岩石力学试验。结合水布垭水利枢纽大坝建基岩体工程质量评价实例,对岩体工程质量分级的应用进行了研究。 相似文献
110.
平板载荷试验应思考的几个问题 总被引:3,自引:0,他引:3
提出了平板载荷试验中的几个问题:(1)复合地基平板载荷试验垫层的重要性;(2)复合地基平板载荷试验存在尺寸效应;(3)单墩或单桩平板载荷试验不完善。重点对目前广泛使用的复合地基荷载试验进行了讨论,以引起检测人员注意。 相似文献