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231.
Existing design procedures for determining the separation distance between adjacent buildings subjected to seismic pounding risk are based on approximations of the buildings' peak relative displacement. These procedures are characterized by unknown safety levels and thus are not suitable for use within a performance‐based earthquake engineering framework. This paper introduces an innovative reliability‐based methodology for the design of the separation distance between adjacent buildings. The proposed methodology, which is naturally integrated into modern performance‐based design procedures, provides the value of the separation distance corresponding to a target probability of pounding during the design life of the buildings. It recasts the inverse reliability problem of the determination of the design separation distance as a zero‐finding problem and involves the use of analytical techniques in order to evaluate the statistics of the dynamic response of the buildings. Both uncertainty in the seismic intensity and record‐to‐record variability are taken into account. The proposed methodology is applied to several different buildings modeled as linear elastic single‐degree‐of‐freedom (SDOF) and multi‐degree‐of‐freedom (MDOF) systems, as well as SDOF nonlinear hysteretic systems. The design separation distances obtained are compared with the corresponding estimates that are based on several response combination rules suggested in the seismic design codes and in the literature. In contrast to current seismic code design procedures, the newly proposed methodology provides consistent safety levels for different building properties and different seismic hazard conditions. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
232.
To study the effect of uncertain factors on the temperature field of frozen soil, we propose a method to calculate the spatial average
variance from just the point variance based on the local average theory of random fields. We model the heat transfer coefficient
and specific heat capacity as spatially random fields instead of traditional random variables. An analysis for calculating the random
temperature field of seasonal frozen soil is suggested by the Neumann stochastic finite element method, and here we provide the
computational formulae of mathematical expectation, variance and variable coefficient. As shown in the calculation flow chart, the
stochastic finite element calculation program for solving the random temperature field, as compiled by Matrix Laboratory
(MATLAB) software, can directly output the statistical results of the temperature field of frozen soil. An example is presented to
demonstrate the random effects from random field parameters, and the feasibility of the proposed approach is proven by comparing
these results with the results derived when the random parameters are only modeled as random variables. The results show that
the Neumann stochastic finite element method can efficiently solve the problem of random temperature fields of frozen soil based
on random field theory, and it can reduce the variability of calculation results when the random parameters are modeled as spatially
random fields. 相似文献
233.
基于环境激励的结构振动测试的方法中ERA方法是重要的时域分析方法.本文主要是以随机减量法(RD)和NExT两种数据处理方法结合ERA算法,对绥化学院正在建的网架结构的基本模态参数进行测试.通过分析比较得出RD/ERA和NExT/ERA较直接ERA有更高的精度,且实测分析结果与有限元分析结果较吻合.为网架结构在环境激励下用ERA方法测试模态参数提供了实验依据. 相似文献
234.
W. H. Ward 《水文科学杂志》2013,58(1):85-101
AbstractA new method is presented to generate stationary multi-site hydrological time series. The proposed method can handle flexible time-step length, and it can be applied to both continuous and intermittent input series. The algorithm is a departure from standard decomposition models and the Box-Jenkins approach. It relies instead on the recent advances in statistical science that deal with generation of correlated random variables with arbitrary statistical distribution functions. The proposed method has been tested on 11 historic weekly input series, of which the first seven contain flow data and the last four have precipitation data. The article contains an extensive review of the results.Editor D. KoutsoyiannisCitation Ilich, N., 2014. An effective three-step algorithm for multi-site generation of stochastic weekly hydrological time series. Hydrological Sciences Journal, 59 (1), 85–98. 相似文献
235.
D.L. De Luca 《水文科学杂志》2013,58(8):1536-1558
AbstractThe spatial and temporal variability of the scaling properties and correlation structure of a data set of rainfall time series, aggregated over different temporal resolutions, and observed in 70 raingauges across the Basilicata and Calabria regions of southern Italy, is investigated. Two types of random cascade model, namely canonical and microcanonical models, were used for each raingauge and selected season. For both models, different hypotheses concerning dependency of parameters on time scale and rainfall height can be adopted. In particular, a new approach is proposed which consists of several combinations of models with a different scale dependence of parameters for different temporal resolutions. The goal is to improve the modelling of the main features of rainfall time series, especially for cases where the variability of rainfall changes irregularly with temporal aggregation. The results obtained with the new methodology showed good agreement with the observed data, in particular, for the summer months. In fact, during this season, rainfall heights aggregated at fine temporal resolutions (from 5 to 20 min) are more similar (relative to the winter season) to the values cumulated on 1 or 3 h (due to convective phenomena) and, consequently, the process of rainfall breakdown is nearly stationary for a range of finer temporal resolutions.
Editor D. Koutsoyiannis; Associate editor A. Montanari 相似文献
236.
李曦凌 《测绘与空间地理信息》2013,(9)
基于Casio fx-9860 G SD型计算器的特性,笔者利用VS2008开发出能够读取、处理维地道路系统生成的Excel直曲表,并能生成计算器能读取的线元串列数据库文件的软件。然后利用生成的串列文件在计算器中进行线路任意里程正反算。实现了公路平面设计参数的自动转换、输入。本文着重介绍软件开发、工程实例中遇到的问题和解决方法。通过多个工程实践证明,该系统可以很好地帮助测量技术人员快速、准确地进行横断面测量、线路中边桩放样、线路地形图等工作,提高了线路测量的效率和规范性。 相似文献
237.
《International Journal of Digital Earth》2013,6(12):1253-1269
ABSTRACTThis study investigates misregistration issues between Landsat-8/ Operational Land Imager and Sentinel-2A/ Multi-Spectral Instrument at 30?m resolution, and between multi-temporal Sentinel-2A images at 10?m resolution using a phase-correlation approach and multiple transformation functions. Co-registration of 45 Landsat-8 to Sentinel-2A pairs and 37 Sentinel-2A to Sentinel-2A pairs were analyzed. Phase correlation proved to be a robust approach that allowed us to identify hundreds and thousands of control points on images acquired more than 100 days apart. Overall, misregistration of up to 1.6 pixels at 30?m resolution between Landsat-8 and Sentinel-2A images, and 1.2 pixels and 2.8 pixels at 10?m resolution between multi-temporal Sentinel-2A images from the same and different orbits, respectively, were observed. The non-linear random forest regression used for constructing the mapping function showed best results in terms of root mean square error (RMSE), yielding an average RMSE error of 0.07?±?0.02 pixels at 30?m resolution, and 0.09?±?0.05 and 0.15?±?0.06 pixels at 10?m resolution for the same and adjacent Sentinel-2A orbits, respectively, for multiple tiles and multiple conditions. A simpler 1st order polynomial function (affine transformation) yielded RMSE of 0.08?±?0.02 pixels at 30?m resolution and 0.12?±?0.06 (same Sentinel-2A orbits) and 0.20?±?0.09 (adjacent orbits) pixels at 10?m resolution. 相似文献
238.
This paper introduces the principle of genetic algorithm and the basic method of solving Markov random field parameters. Focusing on the shortcomings in present methods, a new method based on genetic algorithms is proposed to solve the parameters in the Markov random field. The detailed procedure is discussed. On the basis of the parameters solved by genetic algorithms, some experiments on classification of aerial images are given. Experimental results show that the proposed method is effective and the classification results are satisfactory. 相似文献
239.
针对剩余静校正问题,讨论了统计方法中的蒙特卡罗法用于反射波能量最大化剩余静校正的方法。分别论述了反射波叠加能量最大化法和蒙特卡罗方法,以及蒙特卡罗方法如何应用于剩余静校正的计算中,并用实例说明了该方法的效果。通过实际应用蒙特卡罗剩余静校正方法,解决了经野外静校正后残留的剩余静校正问题,并通过与其他剩余静校正方法的实际应用对比,说明了蒙特卡罗剩余静校正方法的优势。对于大剩余量的静校正问题,蒙特卡罗剩余静校正方法仍然可以很好的解决,并且不会产生串相位问题,说明蒙特卡罗剩余静校正方法是可靠的。 相似文献
240.