Highway bridge seismic design: Summary of FHWA/MCEER project on seismic vulnerability of new highway construction   总被引：2，自引：0，他引：2  

Ian?M.?FriedlandEmail author  Ian?G.?Buckle  George?C.?Lee 《地震工程与工程振动(英文版)》2002,1(1):10-19

The Federal Highway Administration (FHWA) sponsored a large, multi-year project conducted by the Multidisciplinary Center for Earthquake Engineering Research (MCEER) titled “Seismic Vulnerability of New Highway Construction” (MCEER Project 112), which was completed in 1998. MCEER coordinated the work of many researchers, who performed studies on the seismic design and vulnerability analysis of highway bridges, tunnels, and retaining structures. Extensive research was conducted to provide revisions and improvements to current design and detailing approaches and national design specifications for highway bridges. The program included both analytical and experimental studies, and addressed seismic hazard exposure and ground motion input for the U.S. highway system; foundation design and soil behavior; structural importance, analysis, and response; structural design issues and details; and structural design criteria. Supported by: the Federal Highway Administration under contract number DTFH61-92-C-00112.  相似文献   

Effects of Soil Composition on Zn Speciation in Drainage Waters from Agricultural Soils     

Hanbin?XueEmail author  Phan?Hong?Nhat  Laura?Sigg 《Aquatic Geochemistry》2005,11(3):303-318

The influence of Zn speciation on Zn transport by drainage from different soils to surface water is examined in a stream catchment in an agricultural area. Drainage waters were collected from two types of soils, a mineral soil (MS) and a soil rich in organic matter (OS) by means of artificial drainage pipes. The speciation of dissolved Zn in the stream and the drainage waters was determined using ligand-exchange and voltammetry. About 50–95% of dissolved Zn is bound in strong complexes, and the free Zn²⁺ ion concentration is in the range of 1–16% of dissolved Zn. A substantial part of Zn is present in weaker organic or inorganic complexes. The simulated Zn speciation using the WHAM VI model is compared to the determined speciation. Free Zn²⁺ concentrations predicted by the WHAM VI model are generally higher than the analytically determined free Zn²⁺, but are mostly within the same order of magnitude. Effects of different soil organic matter content on Zn speciation and transport are discussed. Zn speciation in the drainage at the OS site is influenced by the distribution of organic matter between the solid and solution phase. The abundant organic Zn complexes in solution contribute to facilitate Zn transport from soil into surface waters, through the drainage at the OS site. Drainage from the OS site contributes about twice as much Zn input to the receiving water as the MS soil, as related to specific area. The mineral soil contains much lower organic matter, and a part of Zn bound with inorganic phases can hardly be released by dissolved organic ligands, leading to much higher Zn retention at the MS site.  相似文献   

Modal model identification of structures under unmeasured seismic excitations     

Vincenzo Sepe  Danilo Capecchi  Maurizio De Angelis 《地震工程与结构动力学》2005,34(7):807-824

Techniques developed for structural identification of a structural model are typically based on information regarding the response and the forcing actions. However, in some situations it can be necessary, or simply useful, to refer only to the measured responses. In this paper we describe a technique suitable for identifying the modal model of a spatial frame in the frequency domain when the seismic input is unknown both in time contents and direction. In some previous theoretical works we established that this identification problem has a unique solution when at least three time‐history responses are known. Here numerical techniques are developed which allow the evaluation of the modal quantities in practice. Numerical applications are carried out on plane and spatial framed structures by using a modal model which may be complete, including all the structure's modes, or incomplete, including only the lowest modes. In most cases the obtained results are satisfactory. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Estimate of input energy for elasto‐plastic SDOF systems during earthquakes based on discrete wavelet coefficients     

Jun Iyama 《地震工程与结构动力学》2005,34(15):1799-1815

The response of an elasto‐plastic single degree of freedom (SDOF) system to ground motion is estimated based on wavelet coefficients calculated by discrete wavelet transform. Wavelet coefficients represent both the time and frequency characteristics of input ground motion, and thus can be considered to be directly related to the dynamic response of a non‐linear system. This relationship between the energy input into an elastic SDOF system and wavelet coefficients is derived based on the assumption that wavelets deliver energy to the structure instantaneously and the quantity of energy is constant regardless of yielding. These assumptions are shown to be valid when the natural period of the system is in the predominant period range of the wavelet, the most common scenario for real structures, through dynamic response analysis of a single wavelet. The wavelet‐based estimation of elastic and plastic energy transferred by earthquake ground motion is thus shown to be in good agreement with the dynamic response analysis when the natural period is in the predominant range of the input. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Bound of earthquake input energy to soil–structure interaction systems     

Izuru Takewaki   《Soil Dynamics and Earthquake Engineering》2005,25(7-10):741-752

A new critical excitation method is developed for soil–structure interaction systems. In contrast to previous studies considering amplitude nonstationarity only, no special constraint of input motions is needed on nonstationarity. The input energy to the soil–structure interaction system during an earthquake is introduced as a new measure of criticality. It is demonstrated that the input energy expression can be of a compact form via the frequency integration of the product between the input component (Fourier amplitude spectrum) and the structural model component (so-called energy transfer function). With the help of this compact form, it is shown that the formulation of earthquake input energy in the frequency domain is essential for solving the critical excitation problem and deriving a bound on the earthquake input energy for a class of ground motions. The extension of the concept to MDOF systems is also presented.  相似文献   

1∶25万修测区数字地质填图前人剖面资料录入、验证的工作方法——以广西1∶25万玉林市幅为例     

覃小锋  周开华  胡贵昂  周府生  李广宁  谢凌峰 《华南地质与矿产》2005,(1)

进行过大量 1∶5万区调填图、研究程度较高地区的 1∶25万区域地质调查,其核心任务是充分挖掘利用前人资料及二次开发,在广西 1∶25万玉林市幅PRB数字填图试点过程中,经过两年多来的摸索研究,初步总结出一套前人剖面资料录入、验证、批注、修测和成图过程的工作方法,已基本上达到了在 1∶25万区调修测区推广应用的“实战性”要求。  相似文献   

地震分析中人工边界处理与地震动输入方法研究   总被引：8，自引：0，他引：8  

邱流潮  金峰 《岩土力学》2006,27(9):1501-1504

基于柱面波波动方程,推导建立了适用于土-结构地震动力相互作用分析的地震动输入和人工边界的处理方法.其中,地震动的输入是通过在人工边界上施加等效节点力来实现的,等效节点力的大小与入射地震波波速成正比;而人工边界的处理方法使得人工边界条件不仅在时间上是局部的,而且在空间上也是局部的.这种处理方法简单、有效,物理意义清晰,且很容易在有限元法中实现,结合Newmark时间积分是无条件稳定的.为了验证方法的有效性和精度,给出了两个算例,分别用于检验人工边界条件的性能以及地震动输入方法的正确性.算例分析结果表明,所提出的方法是十分有效的.  相似文献   

中国化肥投入管制的时空演化及影响因素分析   总被引：1，自引：0，他引：1  

杨建辉 《地理科学》2018,38(9):1516-1524

运用脱钩弹性方程,分析了1980~2015年中国各地区（除港澳台地区外）的化肥投入与农业增长耦合关系和化肥投入变动的管制效果;通过LMDI模型,将化肥投入变动影响因素分解为产值规模效应、化肥效益效应和科技效应。研究表明：随着农业经济的迅速发展,中国的化肥投入可以分为“增量管制”和“减量管制”2个阶段,减量管制阶段的化肥投入增速明显低于增量管制阶段,其中东部地区的化肥投入率先减量;脱钩弹性系数在增量管制阶段末期达到最高值后,呈现出逐渐降低的趋势,各地区的管制效果与化肥投入管制方向基本相同;科技效应驱动了各地区化肥投入的减少,化肥效益效应是化肥投入增加的推动力,各效应在增量管制和减量管制阶段的驱动方向保持一致,其中东部地区的化肥效益效应贡献率较大,同时科技效应贡献率的绝对值也相对高,西部地区农业增产模式较为粗放。随着化肥投入减量管制的深入,要在重视空间差异的基础上,不断提高化肥增产效率、增强现代农业的外部替代作用。  相似文献   

珠江口盆地Site4B柱状沉积物中脂肪醇分子化合物分布及其来源分析     

茅晟懿  朱小畏  孙永革  管红香  吴能友 《海洋与湖沼》2014,45(6):1202-1217

本研究采用色谱质谱(GC-MS)和色谱-同位素质谱(GC-IRMS)方法,对珠江口盆地Site4B沉积物中脂肪醇分子化合物分布以及单体碳同位素组成进行了研究。结果表明:长链脂肪醇碳优势指数(CPIC26—34:9.41—24.56)、平均碳链长度(ACLC26—34:28.85—29.99)以及n C26—n C30脂肪醇平均碳同位素组成(?29.13‰±0.87‰、?32.98‰±1.28‰和?32.73‰±1.61‰)均揭示了n C26—n C34脂肪醇属于陆源高等植物来源,n C16—n C20和n C24脂肪醇较正的碳同位素组成反映了化合物的海洋细菌来源,而n C22脂肪醇偏负的碳同位素特征(平均?33.26‰±1.51‰)反映了化学自养细菌来源。Site4B沉积物中的陆源输入主要来自南海周边河流,从12.7ka BP至今的沉积时期(0—80cm,文中深度均为埋深)和末次冰盛期(102—120cm),其陆源输入主要来自台湾岛河流,而在19.3—12.7ka BP沉积时期(80—102cm)和更新世沉积时期(120—300cm),台湾岛、吕宋岛和珠江口河流的陆源贡献普遍较低。Site4B沉积物中的海洋生产力主要来自海洋微生物输入的贡献,并主要受到海水温差影响;其中在35—150cm层位,海洋输入和南海暖流的强弱带来的海水温度的高低有关,而在150—300cm层位,则主要和冰期-间冰期的冷暖气候带来的海水温差有关。  相似文献   

输出非线性方程误差类系统递推最小二乘辨识方法     

丁锋  陈启佳 《南京气象学院学报》2015,7(3):193-213

随着控制技术的发展,控制对象的规模越来越大,使得辨识算法的计算量也越来越大.对于结构复杂的非线性系统,特别是包含未知参数乘积的非线性系统,使得过参数化辨识方法的参数数目大幅度增加,辨识算法的计算量也急剧增加,因此探索计算量小的参数估计方法势在必行.针对输出非线性方程误差类系统,讨论了基于过参数化模型的递推最小二乘类辨识方法;为减小过参数化辨识算法的计算量和提高辨识精度,分别利用分解技术和数据滤波技术,研究和提出了基于模型分解的递推最小二乘辨识方法和基于数据滤波的递推最小二乘辨识方法.最后给出了几个典型辨识算法的计算量、计算步骤、流程图.  相似文献