输电线路覆冰灾害分析及防治

介绍了覆冰的形成和分类以及国内外关于覆冰模型的研究,总结出覆冰对于输电线路的危害,推算了覆冰作用下输电塔所受风荷载、导地线荷载。在此基础上,从现场处置措施和安全管理方面,对输电线路覆冰灾害的防治提出了几点建议,以减少不必要的损失。     

输电线路覆冰研究综述

输电线路覆冰是一种严重的自然灾害,可引发输电线路过荷载、导线舞动、绝缘子串闪络等事故,严重危害电力系统的安全运行。总结和分析了国内外输电线路典型覆冰事故、覆冰的种类与性质、影响覆冰的因素、绝缘子冰闪特性的研究以及输电线路覆冰机理的研究。分析结果表明:绝缘子覆冰闪络问题日渐突出;影响绝缘子覆冰的因素很多,其中电场对绝缘子覆冰的影响不容忽视。     

输电铁塔风荷载作用下剩余寿命的计算方法分析

鉴于输电铁塔在强风作用下，非线性特征影响较大，对风荷载作用下的输电铁塔进行了疲劳分析。给出了工程应用实例，结果合理。     

输电线路覆冰过大对输电铁塔的强度影响

覆冰会导致输电铁塔的荷载增大,影响电网正常运行,严重时还会引起铁塔倒塌。针对由于覆冰过大引起的垂直荷载与横向荷载,分析输电导线覆冰过大情况下对输电导线的安全性影响,对覆冰厚度逐渐增大时输电铁塔的强度影响行进研究,为输电线路设计和安全提供了参考。     

谈铁塔荷载组合

介绍了作用在输电线路杆塔上的荷载的类型,着重对风速取值、杆塔荷载、杆塔角度风分配进行了计算分析,并对直线塔与转角塔的荷载组合工况进行了阐述,以供参考。     

特高压输电线路重冰区荷载及荷载组合研究

分析研究了±800 k V线路输电杆塔的荷载作用特点,总结了特高压输电铁塔的荷载计算方法和荷载组合。在保证输电线路工程安全运行的前提下,经济合理的解决了重冰线路设计难题。     

断线张力下覆冰输电塔极限承载力研究

冰冻灾害下,覆冰荷载导致输电塔架的破坏较为严重,而断线张力是引起倒塔的主要因素.利用非线性有限元理论,针对覆冰500kV猫头式输电塔,研究了10种加载模式下的极限承载力和破坏形式.计算结果表明,不同的加载模式下输电塔的破坏形式可以分为塔架局部弯曲失稳破坏、加载点位置的强度破坏和整体失稳破坏3种.论述了覆冰荷载的增加对不...     

220 kV猫头型输电塔在覆冰与断线耦合作用下的响应研究

利用弧长法有限元分析了猫头型输电塔在覆冰与断线耦合作用下的响应,研究了杆塔受弯、受扭及受弯扭的承载力变化规律、内力分布与变化规律、应力分布规律及斜材面外变形分布与变化规律,分析了不同塔型的破坏特征及覆冰厚度对杆塔承载力的影响。研究结果表明：杆塔在覆冰与断线耦合作用下,受弯使得受压侧主材及刚度突变处杆件屈服;受扭时塔头与塔身顶层横隔受力较大,使得其下方斜材屈曲;受弯扭导致塔底受压侧主材屈服及塔身斜材屈曲;杆塔覆冰后自重的增加会加剧其受压侧主材屈服及斜材屈曲,降低杆塔在断线荷载下的抗侧能力,在设计中应考虑覆冰与断线耦合作用对杆塔性能的影响。     

跨越高速铁路输电杆塔可靠度分析

研究了跨越高速铁路输电杆塔可靠度水平,对跨越高铁电力线路安全可靠性进行评价。根据实际工程,采用ABAQUS有限元分析软件,建立了包含两基直线塔、两基耐张塔与三跨输电线的输电塔-线体系三维有限元模型。采用改进的一次二阶矩法(JC法)计算输电杆塔单根杆件可靠指标,利用窄界限法对杆塔体系可靠指标进行分析。综合考虑了0°,45°,60°以及90°风等荷载与覆冰荷载共同作用的影响,基于MATLAB软件编制的计算程序,分别计算了各工况下杆塔的可靠指标。研究结果表明:在设计风速下,考虑覆冰荷载时,呼高48,51 m的杆塔中可靠度水平最低的杆件均位于塔的横担处;呼高48,51 m的输电杆塔的整体可靠指标分别为3. 518与3. 590,稍低于跨越高铁线路输电线路杆塔目标可靠指标3. 7的要求。     

输电铁塔结构受冰雪荷载作用的破坏原因

冰冻雨雪天气引起超过设计标准的覆冰荷载,使铁塔破坏和倒塌,在具体作用方式上又有所不同,可以大致分为将铁塔压坏、拉坏、扭坏、屈曲失稳破坏以及拉扭共同破坏等几种形式。从输电塔结构的结构形式着手,论述了其在冰雪荷载作用下产生破坏的原因及其力学角度的基本防护措施。     

风荷载作用下输电塔结构体系可靠度分析

用荷载增量法结合有限元分析技术,通过枚举列出输电塔体系的主要失效路径,提出了蒙特卡洛概率方法,并通过Matlab软件计算出各输电塔体系的失效概率,最后以一大型输电塔进行了可靠度计算。     

超高压输电杆塔结构体系可靠性研究

应用载荷增量最小准则法识别超高压输电杆塔结构体系的主要失效模式,同时结合blatlab优化工具箱。编制可靠度计算程序,工程算例计算结果表明现行超高压输电杆塔结构体系可靠度指标偏低,应适当提高。     

风载作用下四角钻塔的有限元分析

介绍了钻塔的基本概况及ANSYS软件的应用，分析比较了应用ANSYS有限元软件和图解法对钻塔的设计，说明了应用ANSYS有限元软件用于铁塔的设计是可行的，而且精度很高。     

An incremental load formulation for limit states in the reliability analysis of nonlinear systems

The present paper outlines a method for system reliability analysis of framed structures considering nonlinear structural behaviour. Limit states are formulated using an incremental load formulation in differential form considering both random strengths and stiffnesses. The first order partial derivatives thus obtained can directly be used in the First Order Reliability Methods.

A simple example study is presented to illustrate the formulation and the importance of the refinements included compared to earlier formulation. The application of the approach to more general non-linear structures is outlined.     

高压输电塔地震作用下的连续性倒塌分析

利用大型有限元分析软件ABAQUS和开发的子程序,分别对某输电塔进行了单向地震作用和三向地震作用下的连续性倒塌分析,研究了输电塔的薄弱部位和连续性倒塌全过程。分析结果表明,采用编制的子程序可以确定输电塔的薄弱部位,可以清晰地得到输电塔在地震作用下的连续性倒塌全过程,输电塔在三向输入作用下更容易发生倒塌。     

组合载荷作用下冷却塔的应力分析

针对某工程组合荷载对冷却塔应力分布的影响问题，用一般的薄壳有限元分析方法，计算了某冷却塔在风载和温度载荷作用下冷却塔应力的分布，对塔的安全性进行了评估。     

Performance evaluation of a transmission tower by substructure test

In this paper, a half-scaled substructure test was performed to evaluate the failure mode of an existing transmission tower subjected to wind load. A loading scheme was devised to reproduce the dead and wind loads acting on the prototype transmission tower. The load was enforced on the model structure using two actuators and a triangular jig mounted on the reduced model. Preliminary numerical analysis was carried out to evaluate the stability and member force of the specimen for the design load. When the substructured transmission tower was loaded by 270% of its maximum allowable buckling load, local buckling occurred in joints of leg members with weak constraints. From the experimental results, such as load-displacement curves, displacements, and strains of members, it was concluded that the local buckling was due to the additional eccentric force caused by unbalanced deformation of the specimen.     

输电塔架与输电塔-线耦联体系风振响应风洞试验研究

为研究高压输电塔-线耦联体系与输电塔架的风振动力响应特点,以某典型500kV高压输电线路结构为原型,设计制作了单塔与塔-线体系的完全气弹模型,进行了多个风向角、多级风速下的单塔和塔-线体系在紊流风场中的完全气弹模型风洞试验。试验结果表明:在紊流风场中,输电塔结构的顺风向响应和横风向响应处于同一数量级,塔-线体系与单塔相比,其风致敏感性增强,塔-线模型中输电塔的振动较单塔振动复杂,塔顶位移响应较单塔增加幅度较大,强风时塔-线体系的耦合振动现象较为明显,其振动响应表现出非线性系统特有的动力现象,振动过程中系统自振特性不断变化,风致振动激起了线性系统未有的振动频率。输电塔-线体系的结构设计需合理考虑输电塔与输电线的耦合振动对结构动力特性的影响。     

Failure mechanism and retrofitting strategy of transmission tower structures under ice load

An experimental study was conducted on two pairs of subassemblages of a typical 500 kV transmission tower of the same type as those suffered the most severe damage during ice disaster in South China in 2008. The objectives are to study the failure mechanism of transmission towers under extreme load of freezing rain and to investigate the pertinent retrofitting strategy for increasing the load-carrying capacity of towers so as to prevent their collapse. The difference between specimens in each pair is that one had an additional diaphragm as measures of retrofitting while the other did not. The mechanical behavior, failure mode, strain and deformation at critical points, of the specimens were studied. The test results revealed that buckling of the main leg was the predominant failure mode of structures. For the two subassemblages without diaphragm, the out-of-plane deformations in the joints of diagonal bracings were relatively large and the buckled main angle members exhibited apparent torsion, which significantly decreased the load-carrying capacity of specimens. But for the two subassemblages with diaphragms, the out-of-plane deformations of cross-bracings were markedly inhibited by the added diaphragms and the buckling mode of the main member approached flexural buckling without torsion. As a result, the ultimate strength was increased by 18.3% and 17.6% for the single-panel and double-panel tower subassemblages respectively. It shows that the addition of the diaphragm significantly improved the mechanical performance of transmission towers by reducing the torsional effect on main members and inhibiting the out-of-plane deformation of diagonal braces.     

First-order reliability method-based system reliability analyses of corroding pipelines considering multiple defects and failure modes

A methodology that employs the first-order reliability method is proposed to evaluate the time-dependent system reliability of a segment of a pressurised steel pipeline containing multiple active corrosion defects. The methodology considers the leak and burst failure modes of the pipe segment and takes into account the correlations among limit state functions at different corrosion defects. The methodology involves first constructing two linearised equivalent limit state functions for the pipe segment in the standard normal space and then evaluating the probabilities of leak and burst of the segment incrementally over time based on the equivalent limit state functions. The applicability and accuracy of the proposed methodology is illustrated through system reliability analyses of three pipeline examples, each containing ten active corrosion defects whose growth over time is characterised by the linear, nonlinear and homogeneous gamma process-based models.