【作者】 张建丽；

【导师】 雷宏刚；

【作者基本信息】 太原理工大学 ， 结构工程， 2019， 博士

【摘要】 网架结构广泛应用在带悬挂吊车的工业厂房中。随着悬挂吊车数量和吨位的增加,网架结构的疲劳问题日趋凸显。由于相关的理论与试验研究较少,至今国内外规范中均未确定与之相对的疲劳设计方法,严重制约了网架结构在工业厂房中的推广应用。网架结构的疲劳关键是节点连接的疲劳。在国家自然科学基金项目(51578357)的资助下,本文针对网架结构焊接空心球节点钢管焊趾处的疲劳性能开展了试验及理论研究,主要研究工作及结论如下:1、借助焊接空心球节点的静力试验和有限元分析,得到了焊接空心球节点的表面应力分布规律以及节点钢管焊趾处热点应力集中系数的数值解,为以热点应力幅为参量建立钢管焊趾处的疲劳设计方法奠定了基础。2、借助美国MTS疲劳试验机开展了38个足尺焊接空心球节点的常幅疲劳试验,得到了24个有效数据点。通过对数据的回归分析得到了焊接空心球节点钢管焊趾处的疲劳曲线。基于此疲劳曲线,分别以名义应力幅和热点应力幅为参量,建立了焊接空心球节点钢管焊趾处的疲劳设计方法。3、将红外热像法应用于足尺焊接空心球节点的疲劳试验研究中。通过分析试件表面的温升预测节点的疲劳破坏位置,得到裂纹贯穿壁厚对应的循环次数。4、在对33个疲劳断口进行宏观分析的基础上,借助扫描电镜对11个典型疲劳断口进行微观分析,得到了焊接空心球节点钢管焊趾处疲劳断口的形貌特征,揭示了焊接空心球节点钢管焊趾处的疲劳破坏机理。5、选择合适的断裂力学参数,采用Paris公式估算焊接空心球节点钢管焊趾处的疲劳寿命。对于具有焊接缺陷的试件,公式估算的疲劳寿命与试验疲劳寿命几乎接近。对于无明显焊接缺陷试件,公式估算的疲劳寿命与试验疲劳寿命规律性一致。本文的研究成果为焊接空心球节点相关疲劳设计规范的修订提供了参考依据,对焊接空心球节点网架结构在工业建筑中的应用起到推动作用。更多还原

【Abstract】 Grid structures have been widely used in industrial buildings with suspending cranes.With the increasing of suspending cranes in quantity and size,the fatigue problem of grid structures has been more and more highlighted.Since the related theoretical and experimental researches are limited,fatigue design methods for grid structures are currently lacking at home and abroad.Hence,the applications of grid structures in industrial buildings have been seriously restricted.The fatigue of joints is very important to the fatigue of grid structures.Funded by Chinese National Science Foundation Project(51578357),the experimental and theoretical research on the fatigue properties of the weld toe in steel tube of welded hollow spherical joints in grid structures was conducted.The main research work and conclusions are as follows:1.The stress distribution of the welded hollow spherical joints was obtained by the static loading tests and finite element analysis.Then,the formula of the hot spot stress concentration factor of the weld toe in steel tube was derived.It provided the foundation for fatigue design methods of the weld toe in steel tube of welded hollow spherical joints on the basis of hot spot stress amplitude.2.The constant amplitude fatigue tests of 38 full scale welded hollow spherical joints were conducted using the MTS fatigue testing machine system.24 effective test data were obtained and fitted to a fatigue curve for the weld toe in steel tube by regession analysis.Based on the curve,the fatigue design methods were established by adopting the nominal stress and the hot spot stress respectively.3.The infrared thermal method was applied to the fatigue test of full scale welded hollow spherical joints.The fatigue damage position of the joint was predicted by analyzing the temperature rise of the surface of the joint.The cycle numbers were obtained when the crack penetrated the wall thickness of the joint.4.Macroscopic analysis of 33 fatigue fractures and microscopic analysis of 11 typical fatigue fractures by scanning electron microscopy were conducted.Morphological features of fatigue fracture of the weld toe in steel tube of welded hollow spherical joints were obtained.Then,the fatigue failure mechanism of the weld toe in steel tube of welded hollow spherical joint was revealed.5.By selecting the appropriate fracture mechanics parameters,Paris formula was used to estimate the fatigue life of the weld toe in steel tube of the welded hollow spherical joints.For the specimens with welding defects,the fatigue life could be estimated accurately.For specimens without obvious welding defect,the regularity is consistent between estimated fatigue life and experimental fatigue life.The research results of this paper will provide references for the revision of fatigue design methods of welded hollow spherical joints and promote the development of grid structures with welded hollow spherical joints in the industrial buildings.更多还原