数值模拟在土木工程中的应用（英文）

本文针对当前土木工程领域数值模拟是否进一步应用的争议进行了深入剖析,介绍了国内数值模拟在以下方面的应用现状:评价和预测混凝土结构的寿命、抗连续倒塌、基坑工程、抗震、火灾下的结构演化、桥梁、结构动力分析、风荷载效应、钢结构等。本文还指出了数值模拟在土木工程应用中现存的问题及解决办法,总结了数值模拟的应用特点,指明了研究方向。     

土木工程随机风场数值模拟研究的进展

风荷载是大跨空间结构、高层和高耸结构、桅式结构、大跨度桥梁等土木工程结构的主要设计荷载之一.风荷载的确定手段主要有风洞试验、现场实测、数值模拟等.但前两类风荷载确定手段均较为复杂,且耗时耗资巨大,因而仅仅针对特定的工程结构才进行.通过数值模拟方法得到的风速时程满足风主要统计特性的任意性, 而且比实际记录更具有代表性, 因而在实际工程中被广泛使用.首先简要介绍大气边界层风的特性与风荷载的作用特点,接着重点讨论了土木工程风工程中平稳高斯、非平稳高斯、非高斯随机风场的模拟技术,最后对该领域的进展情况给出了一些展望.     

土与结构物接触面特性研究

土与结构接触面力学特性和数值模拟的研究，是土木工程中的一个重要课题，本文系统简述了接触面力学性和数值模拟的研究现状，指出了接触研究中存在的问题，并提出了接触面研究可能的发展方向。     

调谐型颗粒阻尼器简化力学模型及其参数计算方法研究与减震桥梁试验

介绍了调谐型颗粒阻尼器, 进行了基于该阻尼器减震高架连续梁桥缩尺模型的振动台试验;建立了该阻尼器的数值分析简化力学模型, 提出了该模型等效阻尼比的能量估算方法, 并对该阻尼器的减震控制效果进行了有限元数值模拟. 试验与数值模拟结果表明:调谐型颗粒阻尼器可以有效降低高架连续梁桥的地震响应;上述简化力学模型和参数估算方法可以有效模拟调谐型颗粒阻尼器的减震控制效果, 可为基于颗粒阻尼器的土木工程结构减震设计参考.     

颗粒阻尼技术的研究综述

介绍了颗粒阻尼技术的基本概念,耗能机理,以及国内外的应用情况和研究概况;系统阐述了颗粒阻尼的理论分析、数值模拟以及试验研究的发展,指出了其优缺点,并简述了多自由度结构附加颗粒阻尼器的离散元模拟方法;重点介绍了颗粒阻尼技术应用于土木工程的实例以及相应的研究情况,指出其在应用中的诸多优点及使用潜力,同时也明确了目前研究中的难点和不足,并提出了建议。     

利用振动模态参数对一空间复合结构梁的损伤检测的探讨

利用振动模态识别法对结构损伤进行诊断作为一种无损检验的方法,现已广泛应用在航天、航空、机械、造船、土木工程等多个领域.本文将对振动参数识别法做进一步的讨论和验证.文中将通过改变模型单元刚度模拟其结构损伤,利用有限元结构动力分析程序对该模型在“损伤”前后进行了结构动力分析.数值仿真计算结果表明：不同程度的损伤对结构各阶的频率、振动模态具有不同程度的影响;结构损伤前后的振动模态变化对“损伤”较为敏感,利用其模态的变化能对结构损伤实现有效定位.     

耦合离子与水化产物间相互作用的水泥基材料氯离子传输模型

钢筋混凝土结构为土木工程领域应用最广泛的结构形式,而氯离子诱发的钢筋锈蚀为降低混凝土结构耐久性的主要原因之一。在以往的研究中,基于Nernst-Planck方程的数值模型通常被用来模拟混凝土中离子的传输,进一步预测混凝土结构的服役寿命,然而这些数值模型并未考虑传输过程中离子与水化产物之间的热力学作用。因此,本文基于离子传输的物理化学作用的本质过程,建立了饱水状态下水泥基材料中多离子传输的数值模型。首先,采用表面络合模型和相平衡模型,建立了孔溶液中离子与水化产物间的热力学数值模型;然后,借助于算子分裂算法,求解了耦合热力学作用的Nernst-Planck方程多离子传输的有限元模型,得到了水化产物中各相成分、孔隙率及孔溶液中各自由离子浓度的演化规律。最后,通过已有文献的试验研究验证了本文建立的数值模型的准确性。     

土木工程结构损伤诊断的几种方法探究

在我国,土木工程结构的应用范围最广,土木结构具有尺寸大、总量轻等特点,这使得土木工程结构存在先天缺陷。土木工程结构在使用中极容易受到环境和非结构构件等因素的影响,在这些因素的作用下,土木工程结构会出现损伤。为了确保土木工程结构的安全,必须要及时的对这些损伤进行识别和诊断,避免因土木工程结构稳定性问题导致质量和安全事故。本文主要分析了土木工程结构损伤的危害及损伤诊断的内涵,并详细介绍了几种损伤诊断方法。     

量测模态数量对结构损伤识别影响数值模拟研究

基于不完备信息开展土木工程结构损伤识别研究是一个热点、难点问题。利用结构部分节点振型分量以及低阶固有频率对一两层框架结构进行了损伤识别数值模拟研究,着重考察了量测模态数量对损伤识别精度的影响,为实际结构损伤识别信息的选取提供了一定依据。     

小波变换在密集模态结构参数识别中的应用

系统研究了小波变换在具有低频密集模态的土木工程结构参数识别中的应用。采用Morlet小波，首先阐述了该方法识别模态频率和模态阻尼比的基本原理；分析了其时间和频率分辨率，针对土木工程结构中低频模态密集的情况，提出了选择小波参数的具体方法。通过三自由度结构的数值分析验证了该方法的正确性和优越性。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.     

新闻(英文)

正China and Greece Sign the Standardization Cooperation Agreement Witnessed by Chinese Premier Li Keqiang and Greek Prime Minister Antonis Samaras,AQSIQ Minister Zhi Shuping and ELOT Chairman and Executive Director Angelos Tolkas signed the SAC-ELOT Standardization Cooperation Agreement.The Agreement is one of the critical cooperation documents signed during Li Keqiang’s visit in Greece,encouraging China and Greece to