Categorisation and Harmonisation of Probabilistic Earthquake Hazard Assessments with Respect to Statistic Representation of Input Data     

V. Schenk  Z. SchenkovÁ  P. Kottnauer 《Natural Hazards》1997,15(2-3):121-137

Probabilistic hazard calculations were tested with respect to input data uncertainties. Statistical approximations of input data allow the regression coefficients and their standard deviations to be determined. Since inaccuracies of the regressions closely depend on the input data uncertainties, the standard deviations of the individual coefficients were used as a measure of input data parametrisation. Differences in the hazard outputs, caused only by various combinations of the regression coefficients and their standard deviations determined for the cumulative recurrence graph and the attenuation law, were studied. It was concluded that the hazard calculation conditions should be (a) strictly defined and always quoted with every hazard assessment, and (b) standardized in order to establish a common liability of earthquake hazard calculations. The established categorisation of the earthquake hazard assessments divides the probabilistic hazard calculations according to their reliability and helps users to apply them in earthquake engineering practice. The credible hazard assessments corresponding to 90% probability can be recommended for common structures whereas the maximum credible hazard assessments coinciding with 95% probability yield values close to hazard assessments of important structures, hospitals, bridges, etc.  相似文献   

Duration of strong ground motion during Mexican earthquakes in terms of magnitude,distance to the rupture area and dominant site period     

Eduardo Reinoso  Mario Ordaz 《地震工程与结构动力学》2001,30(5):653-673

A study of the duration of strong ground motion using accelerometric data of subduction and normal‐faulting Mexican earthquakes is presented. Duration is obtained based on the time between 2.5 and 97.5 per cent of the Arias intensity. An expression to predict this duration in terms of the magnitude, distance to the rupture area and site period is proposed and compared with predictions available in the literature. The effect of large duration for very distant sites and the contribution of soft soils to the duration of strong ground motion are widely discussed. We have found that large magnitude not only yields long duration at the source, but also proportionally longer duration with distance and with dominant site period compared to small magnitude. The duration obtained from the regression is used as a parameter to obtain input and hysteretic energy and on the use of damage models available in the literature. Finally, duration is used together with the random vibration theory to predict response spectra. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Alkalinity buildup during silicate weathering under a snow cover     

Robert A. Berner  Ji-Long Rao 《Aquatic Geochemistry》1996,2(4):301-312

Results from the study of experimental plots at Hubbard Brook, New Hampshire for the years 1987, 1988, 1993, 1994, 1995, and 1996 show that the water draining from under a plot planted with pine trees exhibits its highest alkalinity during the year at about the time of spring snowmelt. This high alkalinity is believed to be due to buildup during the winter under a snow cover. The soil solutions are protected from acidic precipitation by the snow, and the natural process of the reaction of organic acids and carbonic acid with minerals and exchange complexes to form dissolved HCO₃ ^– (and organic anions) proceeds with an increase in alkalinity through the winter. When the snow melts the acidic meltwater mixes with, neutralizes and displaces the water previously occupying the soil interstices. This leads to a decided drop in alkalinity of the drainage water. The alkalinity buildup under the pine plot was found to be two to ten times greater than under a similar plot containing no higher plants. This strongly emphasizes the important role of plants, in their ability to produce organic acids and high levels of CO₂, in accelerating the weathering of silicate minerals.  相似文献   

Sediment and heavy metal accumulation in the Cauvery basin   总被引：2，自引：0，他引：2  

A. L. Ramanathan  V. Subramanian  B. K. Das 《Environmental Geology》1996,27(3):155-163

Eleven cores were collected from the Cauvery basin. Radiometric dates were used to determine modern sediment accumulation rates. Sediment accumulation rates ranged from 0.4 to 4 mm yr^–. Heavy metal concentration decreases with the increase of depth. The heavy metal concentrations at certain depths are attributed to the irregular input of metals and their remobilization. Heavy metal accumulations have been computed using sediment accumulation rates, and accumulation rates show an additional anthropogenic input of metals and sediments in the recent past. Factor analysis and correlation analysis show the diverse source and accumulation mechanism influencing the metal distribution in the basin.  相似文献   

一种随时间变化的近区稀释的半解析解     

兰健 《中国海洋大学学报(自然科学版)》1996,(3)

根据基本的扩散方程，以污染物质输入量为已知条件，给出了一种近区稀释的半解析解。该半解析解摆脱了流速是单向的、持续的和定常的条件限制，反映了近区稀释在以潮流场为背景场的状态下，随时间的可变性。  相似文献   

Temporal-moment matching for truncated breakthrough curves for step or step-pulse injection     

Jian Luo  Olaf A. Cirpka  Peter K. Kitanidis 《Advances in water resources》2006

The method of temporal moments is an efficient approach for analyzing breakthrough curves (BTCs). By matching the moments of the BTCs computed through parametric transfer-function models or one-dimensional transport models to those of the data, one can estimate the parameters characterizing the transfer function or apparent transport parameters. The classical method of moments presumes infinite duration. However, the measurement of BTCs is usually terminated prematurely, before the concentration has reached zero. Unless this truncation of the BTCs has been taken into account, the estimates of the parameters may be in error. Truncated measured BTCs are sometimes extrapolated assuming exponential decay. In this study, we use the concept of moments of the truncated impulse–response function [Jawitz JW. Moments of truncated continuous univariate distributions. Adv Water Res 2004;27:269–81] in the analysis of truncated BTCs corresponding to the commonly encountered step and step-pulse injection modes. The method is straightforward, based on the relation, which we derive, between truncated moments of the impulse–response function and the measured BTC. It is practical to apply and does not require the extrapolation of the measured BTC. The method is also accurate. In a numerical study we discuss how short a step-pulse injection may be so that we can approximate it as instantaneous. Finally, we apply the method to the analysis of a field-scale tracer test.  相似文献   

Effects of column axial force – bending moment interaction on inelastic seismic response of steel frames     

Marina Como  Mario De Stefano  Roberto Ramasco 《地震工程与结构动力学》2003,32(12):1833-1852

It is well known that axial force – bending moment interaction (N–M interaction) affects to a large extent the cyclic inelastic behaviour of structural elements, especially columns in framed structures, with reduction in bending capacity and loss of available ductility. A few studies have also shown that significant inelastic axial shortening affects the response of column elements subjected to medium–high levels of axial loads and cyclic bending. This paper is primarily aimed at evaluating the effects of column N–M interaction on the inelastic seismic response of steel frames. By considering the contemporaneous action of vertical loads, due to gravity, and of horizontal seismic excitation, it is shown that the progressive axial shortening of adjacent columns may differ substantially, thus inducing significant relative settlements at the ends of the connecting beams and, then, remarkable amplifications in beam plastic rotations. An evaluation of additional beam plastic rotations induced by column N–M interaction is carried out for real structures by investigating the inelastic response of steel frames designed according to European standards under horizontal and vertical earthquake excitations. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Structural Earthquake Resistance Design Using Energy Method     

HuRongrong 《中国地质大学学报(英文版)》2003,14(2):166-168

A summary of status of researches in the field of structural earthquake resistance design on energy concept is presented in three parts: earthquake input, demands on the structure and supplied capacity of the structure. A new approach is proposed for analysis of the seismic response and damage criteria based on the momentary input energy.  相似文献   

观光农业、农业生产与资金投入的非线性动力学关系--以南京市丹阳镇七仙山玫瑰园为例   总被引：1，自引：0，他引：1  

井玮薇  沙润  林振山  陶卓民 《地理与地理信息科学》2003,19(3):109-112

该文以南京江宁区丹阳镇七仙山玫瑰园为例，建立观光农业、农业生产与资金投入的非线性动力学模式，讨论观光农业、农业生产系统的稳定性问题，研究结果表明：观光农业、农业生产与资金投入三者之间的关系是一种非常复杂的非线性关系，盲目、不切实际的农业生产投资将减小观光农业的规模，而提高农业生产资源的使用价值，将有助于观光农业的发展；在低效率使用农业生产资源的情况下，盲目增加农业生产投入，对农业生产的再扩大和该地区观光农业的发展都是不利的；只有在提高观光农业资源的使用效率和降低农业生产的平均单位投资的前提下，才有可能达到增加农业生产的投入后获得优化该地区的农业生产结构和扩大观光农业规模的目的。  相似文献   

Pseudo‐dynamic testing of bridges using non‐linear substructuring     

A. V. Pinto  P. Pegon  G. Magonette  G. Tsionis 《地震工程与结构动力学》2004,33(11):1125-1146

Pseudo‐dynamic tests on a large‐scale model of an existing six‐pier bridge were performed at the ELSA laboratory using the substructuring technique. Two physical pier models were constructed and tested in the laboratory, while the deck, the abutments and the remaining four piers were numerically modeled on‐line. These tests on a large‐scale model of an existing bridge are the first to have been performed considering non‐linear behavior for the modeled substructure. Asynchronous input motion, generated for the specific bridge site, was used for the abutments and the pier bases. Three earthquake tests with increasing intensities were carried out, aimed at the assessment of the seismic vulnerability of a typical European motorway bridge designed prior to the modern generation of seismic codes. The experimental results confirm the poor seismic behavior of the bridge, evidenced by irregular distribution of damage, limited deformation capacity, tension shift effects and undesirable failure locations. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献