风荷载下在役焊接空间网格结构疲劳性能研究

发布时间：2018-04-27 23:59

本文选题：空间网格结构 + 风荷载　；参考：《东南大学》2015年硕士论文

【摘要】：大跨空间网格结构在风荷载等交变荷载的作用下,结构部分构件的应力变化幅值会很大,可能形成结构的疲劳损伤。同时,工程结构服役的环境往往具有一定程度的腐蚀性,结构构件腐蚀加速了结构构件的疲劳过程,带来的后果往往是灾难性的。因此,对在役大跨空间网格结构进行风荷载作用下的疲劳分析和冗余度评价具有重要的现实意义。风荷载作用下,大跨空间网格结构构件易出现疲劳。本文依据课题组测压风洞模型试验数据确定结构承受的风压时程；应用ANSYS软件,采用梁单元整体模型与壳单元节点模型即局部模型相结合的方式,实现了风致振动响应时程分析,运用雨流计数法统计焊接球节点焊趾处应力循环历程；根据挪威船级社规范提供的相应S-N曲线,结合Miner线性累计损伤理论,计算出空间网格结构构件的疲劳损伤值。若干算例证明了该计算流程的正确性。计算结果表明,结构中最先出现疲劳构件的位置为平均正风压与脉动风压均最大的球壳迎风面；结构中疲劳构件的疲劳损伤值随平均正风压、脉动风压的增大而增大。结构敏感度是用来描述结构行为与设计参数之间关系的响应函数,冗余特性是影响结构鲁棒性的重要因素,体现了损伤情况下的结构安全性。本文借鉴P. C. Pandey方法,认为结构的冗余度与其结构单元的敏感度成反比,以单元的材料弹性模量作为结构参数,将结构参数敏感度定义为荷载作用下的结构响应对材料弹性模量的导数；然后以结构响应敏感度为基础,对风荷载作用下的单层球面网壳的冗余特性进行分析,识别结构的关键构件；并通过与单层球面网壳风荷载疲劳分析结果对比,验证本章分析方法的正确性和有效性。若干算例表明风荷载作用下的低冗余度杆件既包含了疲劳损伤最大的杆件,也包含了应力最大的杆件,低冗余度杆件是结构在荷载作用下易发生破坏的薄弱杆件和关键杆件,结构的冗余度特性能很好地体现结构在荷载作用下的结构薄弱部位。钢结构极易出现锈蚀现象。本文结合文献试验数据,以锈蚀率和最大点蚀深度为基础,对点蚀孔深度、直径及分布情况作出适当假定,提出点腐蚀构件力学性能劣化分析方法,确定不同锈蚀率下点蚀构件的等效弹性模量,并建立试验室和自然大气条件下锈蚀构件力学性能参数的转换关系,提出自然环境下点蚀构件力学性能分析的实用计算方法。最后,对在役空间网格结构分别进行疲劳分析和冗余度评价。结果表明,考虑大气腐蚀作用的影响,结构表面平均正风压与脉动风压最大处易出现疲劳构件；在相同风荷载历程作用下,随着大气腐蚀作用的加重,结构中疲劳杆件数目增加,疲劳杆件疲劳损伤量增大,即大气腐蚀作用对网格结构构件疲劳效应具有促进作用；随着大气腐蚀作用的加重,风荷载下结构构件的冗余度越来越低,但低冗余度杆件和应力及疲劳损伤较大构件仍具有良好的对应性。本文主要创新点：1.将热点应力法应用于风荷载作用下的空间网格结构疲劳分析。2.提出基于点蚀孔深度、直径及分布的腐蚀构件力学性能劣化分析方法。3.实现在役空间网格结构的疲劳分析和冗余度评价,得到其在风荷载下的破坏模式。
[Abstract]:Under the action of alternating load such as wind load, the large span space grid structure can cause a large amplitude of stress variation of structural components, and may form structural fatigue damage. At the same time, the environment of construction service often has a certain degree of corrosiveness, and the corrosion of structural members accelerates the fatigue process of structural members, and the consequences are often the result. Therefore, the fatigue analysis and redundancy evaluation of a large span space grid structure under wind load is of great practical significance. Under wind load, the structural members of large span space grid are prone to fatigue. In this paper, the wind pressure time history of the structure subjected to the wind tunnel test is determined according to the number of wind tunnel test. The application of ANS In YS software, the wind induced response time history analysis is realized by combining the integral model of beam element and the node model of the shell element, that is, the local model, and the stress cycle process of welding joints at welding joints is calculated by using the rain flow counting method. According to the corresponding S-N curve provided by the Norway classification society standard, combined with the theory of Miner linear cumulative damage, the calculation is combined with the theory of linear cumulative damage. The calculation results show that the first fatigue component in the structure is the spherical shell with the highest average positive pressure and fluctuating wind pressure, and the fatigue damage value of the fatigue component increases with the average positive pressure and the fluctuating wind pressure in the structure. Structural sensitivity is a response function used to describe the relationship between structural behavior and design parameters. Redundancy is an important factor affecting the robustness of the structure. It embodies the structural security in the case of damage. This paper uses the P. C. Pandey method as a reference for the structural redundancy inversely proportional to its structural unit sensitivity. The elastic modulus of the material is used as the structural parameter, and the structural parameter sensitivity is defined as the derivative of the elastic modulus of the material under the load action. Then, based on the response sensitivity of the structure, the redundancy characteristics of the single-layer spherical reticulated shell under the wind load are analyzed, and the key members of the structure are identified and through the single layer ball. Comparison of wind load fatigue analysis results of surface reticulated shells verify the correctness and effectiveness of the analysis method in this chapter. Some examples show that the low redundancy rod under wind load includes both the maximum fatigue damage rod and the maximum stress bar, and the low redundancy rod is a weak rod which is easily damaged by the load. The redundancy characteristics of the structure can well reflect the weak structural parts of the structure under the load of the structure. The steel structure is easily corroded. Based on the literature test data, the corrosion rate and the maximum pitting depth are taken as the basis to make the proper assumption on the depth, diameter and distribution of the pitting hole, and the mechanics of the point corrosion component are put forward. The method of performance degradation is used to determine the equivalent elastic modulus of pitting components under different corrosion rates, and to establish the relationship between the mechanical performance parameters of the corroded component under the test room and the natural atmosphere, and put forward a practical calculation method for the analysis of the mechanical properties of the pitting members under natural environment. The results show that, considering the effect of atmospheric corrosion, the average positive pressure of the structure surface and the maximum pressure of the fluctuating wind pressure are easy to appear. Under the action of the same wind load, the number of fatigue bars in the structure increases with the aggravation of the atmospheric corrosion, and the fatigue damage of the fatigue bar increases, that is, atmospheric corrosion. It can promote the fatigue effect of the structural members of the grid. With the aggravation of the atmospheric corrosion, the redundancy of structural members is getting lower and lower, but the low redundancy rod and the stress and fatigue damage component still have good correspondence. The main innovation of this paper is: 1. the hot stress method is applied to the wind load. The fatigue analysis of space grid structure.2. presents a method of deterioration analysis based on the depth, diameter and distribution of pitting holes,.3., to achieve the fatigue analysis and redundancy evaluation of the active space grid structure, and to get the failure mode under the wind load.

【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU312;TU39

【参考文献】