钢桥面板焊接应力分析

焊接钢桥越来越广泛应用,焊接残余应力、变形是对桥梁结构质量与耐久性影响较大。焊接过程中产生残余应力可能会降低桥梁的承载能力和疲劳强度甚至诱发裂纹导致灾难性事故,本文通过有限元方法计算了某大桥桥面板焊接应力和分布情况。     

焊接残余应力对网架负荷加固的影响分析

负荷条件下对网架结构进行加固时,焊接残余应力对网架结构的内力、变形有较大影响。本文结合某网架负荷加固工程,通过运用ANSYS有限元软件对焊接杆件施加等效温度荷载的方式,模拟网架负荷加固杆件焊接时的热胀冷缩。通过相应的应力、变形分析,得出焊接残余应力对网架结构负荷加固的影响。     

大型海洋船舶和巨型门式起重机结构焊接节点的应力分析及焊接方式探讨

对受动载荷作用的船体舯剖面和主机基座以及巨型门式起重机箱形梁、腿的关键结构节点的应力情况及焊接方式进行了分析;并对深熔焊在船舶入级与建造规范标准中的规定和船体结构中的实例运用以及在焊接试验研究的具体情况进行了说明,希望对建筑钢结构工程节点的焊接应用有所启发与帮助,共促发展与提高。     

谈焊接残余应力对结构的影响

综述了焊接残余应力产生的原因、影响因素及其对焊接结构承载力、疲劳强度、刚度、稳定性能和应力腐蚀开裂的影响。最后,对一些减少焊接残余应力的措施进行了探讨,以指导实践。     

深圳京基100大厦441.8m伸臂桁架安装技术

深圳京基100大厦伸臂桁架采用一端刚接、一端铰接的连接方式,避免了由于施工阶段内外筒结构的竖向变形差在伸臂结构中产生过大的初始应力的影响。通过内外筒变形和应力监测结果分析,该连接方式能消除内外筒的竖向变形差,但焊接残余应力对伸臂桁架影响较大。     

损伤和残余应力对钢构件性能的影响

研究累积损伤、厚度方向和纵向残余应力对焊接组合厚板钢构件承载力和刚度的影响,对不同尺寸参数的构件的滞回性能进行了分析比较。结果表明,在静力作用下,累积损伤模型和残余应力对极限承载力的影响微小,对于刚度的影响较大,在低周往复荷载作用下,累积损伤模型和残余应力会使厚度偏大的构件滞回性能减退更加明显。所以采用合理的损伤模型和残余应力有利于正确分析焊接组合厚板钢构件的力学性能,从而增加整体结构的可靠度。     

不同焊接工艺钢结构焊接件的残余应力分析

通过实验测试了不同焊接工艺钢结构焊接件的残余应力,并对实验结果进行了分析。通过分析得出了较大的焊接电流对焊接件产生较大的残余应力的结论,其实验结果对焊接技术工艺实践有指导意义。     

奥氏体316不锈钢焊接工字形截面残余应力的试验研究

不锈钢在建筑结构中的应用逐渐增多,其中包括不锈钢屋盖结构、不锈钢桥梁、不锈钢墙面等结构中的应用。目前国内对不锈钢力学性能的研究相对较少,其中焊接残余应力是影响不锈钢构件焊接影响的一个重要因素,焊接残余应力的分布规律成为迫切需要研究的内容之一。采用分割条带法对奥氏体不锈钢316(06Cr17Ni12Mo2)包括6种截面的焊接工字型钢的纵向残余应力进行测量,通过对测量数据的分析,得到其残余应力的大小和分布特点,为进一步总结焊接不锈钢构件残余应力的分布和残余应力对不锈钢构件的承载力的影响提供了基础。     

用热浸锌部分消除焊接钢管结构残余应力试验研究

焊接钢结构中的残余应力对结构延性有害,一般采用多种附加措施来部分消除残余应力.为考察热浸锌对部分消除残余应力的作用,利用盲孔法,对比测量了焊接钢管结构中3种典型的焊接节点在热浸锌前后的残余应力,介绍了衡量残余应力消除效果的3个评价指标,分析了热浸锌前后残余应力的变化及其原因.研究表明,热浸锌对部分消除构件焊接残余应力具有积极作用,且不要附加投资.最后,给出了钢结构加工过程中的一些建议.     

焊接残余应力对焊接结构的影响

焊接残余应力是焊件产生变形和开裂等缺陷的主要原因,由于其影响因素众多,本文分别从焊接残余应力对结构的刚度、受压杆件稳定性、静载强度、疲劳强度、构件脆性、焊件加工精度和尺寸稳定性等方面进行分析研究残余应力对焊接结构产生的影响。     

张拉应力对ANSYS计算应力强度因子的影响研究

结合有限元裂纹模型,研究了张拉应力的变化对裂纹尖端应力强度因子数值以及最大应力强度和等效应力的影响,并对结构的稳定性进行了数值化分析,指出了模型的危险区域及其变形情况。     

粒间应力、土骨架应力和有效应力

有效应力的概念和有效应力原理对于土力学具有奠基性的意义。但对于诸如"有效应力是虚拟的应力还是真实应力","有效应力方程是否需要修正"等问题在土力学界一直存有争议,尚没有形成共识。在明确有效应力就是不包含孔隙流体压强作用的土骨架应力的基础上,由土颗粒间力的平衡分析和土骨架单元体的平衡分析得到有效应力与总应力以及孔隙流体压强关系的表达式。对于饱和土,这一表达式就是Terzaghi的有效应力方程。表明Terzaghi的有效应力是真实的物理量,具有明确的物理意义,Terzaghi的有效应力方程不需要做任何修正。文中阐明了有效应力、粒间应力和土骨架应力的物理意义及其相互关系。说明在分离考虑孔隙流体压强作用的情况下,有效应力、粒间应力和土骨架应力三者可以是一致的,即不包含孔隙水压强作用的粒间应力和土骨架应力就是有效应力。土骨架应力可以分成孔隙流体压强产生的土骨架应力和有效应力两部分,两者都对土体的变形和强度有贡献,但是作用效果不同。在孔隙流体压强作用对土体的变形和强度的贡献可以忽略的条件下,有效应力决定土的变形和强度。     

Investigation of the stress state of micropiles

Results are presented for monitoring of the stress state of micropiles installed to strengthen the foundations of an industrial building. It is recommended to correct the design of the reinforcing cage of a pile in conformity with its actual serviceability at various depths. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 9–12, September–October, 2008.     

Determination of stress fields in the elastic lithosphere by methods based on stress orientations

Theoretical reconstruction of the stress fields in tectonic plates or particular tectonic regions is an important geophysical problem. Conventional approaches for solving this vital issue are based on classical formulations of boundary value problems of elasticity. In these approaches, stress fields are calculated for diverse boundary conditions defined on the margins of the region in order to fit the experimentally observed orientations of principal stresses inside the region.The present article identifies the major flaw in the conventional approach, which is the impossibility of obtaining a unique and reliable stress field, and suggests alternative methods based on the analysis of orientations of principal stresses. Three methods for determining the elastic state of stress in relatively stable blocks of the lithosphere are described and applied to particular tectonic domains. All of the methods are based on the direct use of experimental data on the stress orientations as input information. The first method exploits direct integration of the equations of elasticity when the field of principal stress trajectories is prescribed within a region. The second one utilizes the non-classical boundary value problem of elasticity, which uses experimentally obtained stress orientations at the region margins as boundary conditions. The third method is aimed at the numerical determination of the stress field from a given set of spatially discrete principal stress orientations.In contrast to the conventional approach, the methods suggested here do not require knowledge of the boundary stress magnitudes. As a consequence, the general solution of the problem becomes non-unique. However, in the case of an elastic medium, only a certain (finite) number of arbitrary parameters control the general solutions. These parameters can be determined from in situ stress measurements within the region under study. Therefore, for the selected spatial scale, the unique stress field can be singled out. In the second method, the number of parameters (and, thus, the minimum number of field measurements) is determined from an analysis of boundary stress orientations alone. In other methods, this number depends upon the harmonicity or non-harmonicity of inclination of the prescribed stress trajectories (for the second method) and the calculated stress trajectories (for the third method).To illustrate the essence of the proposed methods, they are applied to the determination of first-order stress fields in the West European and Australian platforms. These platforms represent two basically different types of stress domains. The stress field for the West European platform reflects nearly homogeneous stress orientations throughout the extent of the region, whereas the Australian platform is characterized by rotation of the principal stress axes while traversing the region margins. In the case of Australia, an important result is the existence (at the chosen spatial scale) of a singular point inside the Australian continent at which the curvature of the stress trajectories is infinite. The local state of stress near such a point has important geophysical and engineering implications.The proposed approaches can be applied not only for the determination of regional stress fields but also at other spatial scales, depending on the scale at which the stress indicators have been characterized.     

论有效应力原理与有效应力

有效应力原理是土力学区别于一般固体力学的基础,是土力学的核心基石。Terzaghi有效应力原理从提出至今就一直饱受争议,特别是有关Terzaghi有效应力的近似性问题是争议的焦点。从有效应力原理的任务出发,阐明有效应力原理的内涵是土体可量测荷载效应—外荷载间的一般规律。指出有效应力的作用是联接土体强度、变形等可量测荷载效应与外荷载间的纽带,定义对土体强度特性和变形行为等可量测荷载效应产生直接影响的土体应力为有效应力,因此,有效应力不是唯一的,它们是土体中真实存在应力的名义表述,可以依据应力平衡原理和流体压力与土颗粒间的相互作用关系给出,不同的有效应力定义就对应不同的有效应力计算公式,从而解释了Terzaghi有效应力原理近似性的原因。提出了强度相关有效应力和变形相关有效应力(Terzaghi有效应力)的概念,严格推导了他们的计算表达式,阐述了强度相关有效应力与土体剪切强度、变形相关有效应力与土体变形的一般关系。进一步,基于莫尔库仑强度准则,推导了土体抗剪强度与Terzaghi有效应力和孔压的关系。     

Life in the fast lane [work stress and stress reduction methods]

This article begins by defining work related stress and outlining stress effects on different employment groups and how they cope with it. It then states that research has found that the relationship between an employee and his/her manager is the single biggest predictor of satisfaction, length of working life, age-work ability and productivity. It concludes by proposing various measures that managers can take in order to reduce employee stress.     

论混凝土温度应力的检测

论述了混凝土温度应力的类型及造成的后果，阐述了温度应力检测与评价的基本原理，结合工程实例，详细介绍了温度应力检测的步骤、方法，提出了检测温度应力并采取相应措施，对于确保工程质量和降低造价具有重大意义。     

Don't stress! [work-related stress]

This article explains how to tackle stress in the workplace. It discusses the causes of stress and the signs and signals to look out for to identify when an individual is suffering from it. It then details a company's responsibilities under the management of health and safety at work regulations and the risk assessment it should carry out to minimize work-induced stress. It concludes by outlining stress management measures that can be taken to alleviate the problem.     

圬工拱桥受力特性仿真分析

以洛泽河桥为分析实例,分别以板单元和实体单元建立了该桥的有限元分析模型,采用不同的分析方法对其进行仿真分析,比较了两种分析方法的合理性及优缺点,并提出合理的圬工拱桥的结构分析方法.