基于断裂力学的钢框架梁柱节点抗震性能分析
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摘要
介绍了8个足尺节点试验的结果与连接焊缝断裂破坏的现象。采用二维有限元断裂模型,研究了抗弯钢框架梁柱节点的断裂行为。以I型裂纹尖端应力强度因子KI和J积分为定量评价指标,分析了焊接孔形式、初始缺陷尺寸及位置、焊接垫板、角焊缝补强等设计细节对节点材料断裂韧性需求的影响。弹性分析表明,切除垫板并以角焊缝补强的措施,能最有效地降低对材料韧性的要求。弹塑性分析表明,焊接高匹配时热影响区裂纹比界面裂纹对材料韧性的要求更高,且局部塑性应变累积使材料的断裂韧性降低;解释了节点试验中断裂易发生在梁下翼缘焊缝热影响区的现象。基于断裂分析得到的节点抗弯承载力与试验中节点的极限弯矩吻合较好,该文的研究为钢框架梁柱节点的防断设计提供了参考。
Experimental results of eight full-scale beam-to-column connections are presented.Two dimensional finite element fracture models are used to simulate the fracture behaviors of the connections which are commonly applied in steel moment resisting frames.Mode I elastic stress intensity factor(KI) and inelastic J-integral(JI) at the crack tip are calculated to provide quantitative estimates of fracture toughness demands of the connections with different design details,such as weld access hole types,initial flaw size & locations,weld backing bars,fillet reinforcement and other configurations.The elastic analyses indicate that the measure of removing the backing bar and reinforcing a fillet weld,is effective to reduce the toughness demand.The inelastic analyses show that the initial crack at weld heat affected zone(HAZ) causes larger toughness demands than the crack at column flange and weld interface when the weld is over matched.The analyses have confirmed the observation in former connection tests that the fractures are more likely to occur at the beam bottom flange weld HAZ area where extensive plastic strains accumulate resulting in low material toughness.The evaluated moments by fracture model analyses agree well with the ultimate moments obtained by the connection tests.This study provides valuable references for the fracture resistant design of beam-to-column connections in steel moment resisting frames.
Experimental results of eight full-scale beam-to-column connections are presented.Two dimensional finite element fracture models are used to simulate the fracture behaviors of the connections which are commonly applied in steel moment resisting frames.Mode I elastic stress intensity factor(KI) and inelastic J-integral(JI) at the crack tip are calculated to provide quantitative estimates of fracture toughness demands of the connections with different design details,such as weld access hole types,initial flaw size & locations,weld backing bars,fillet reinforcement and other configurations.The elastic analyses indicate that the measure of removing the backing bar and reinforcing a fillet weld,is effective to reduce the toughness demand.The inelastic analyses show that the initial crack at weld heat affected zone(HAZ) causes larger toughness demands than the crack at column flange and weld interface when the weld is over matched.The analyses have confirmed the observation in former connection tests that the fractures are more likely to occur at the beam bottom flange weld HAZ area where extensive plastic strains accumulate resulting in low material toughness.The evaluated moments by fracture model analyses agree well with the ultimate moments obtained by the connection tests.This study provides valuable references for the fracture resistant design of beam-to-column connections in steel moment resisting frames.
引文
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[2]Kuwamura H.Classification of material and welding infracture consideration of seismic steel frames[J].Engineering Structures,2003,25(5):547―563.
[3]Kuwamura H,Iyama J,Matsui K.Effects of materialtoughness and plate thickness on brittle fracture of steelmembers[J].Journal of Structural Engineering,ASCE,2003,129(11):1475―1483.
[4]石永久,李兆凡,陈宏,等.高层钢框架新型梁柱节点抗震性能试验研究[J].建筑结构学报,2002,23(3):2―7.Shi Yongjiu,Li Zhaofan,Chen Hong,et al.Experimentalresearch on cyclic behavior of new types ofbeam-column connections in highrise steel frames[J].Journal of Building Structures,2002,23(3):2―7.(inChinese)
[5]Chi W M,Deierlein G G,Ingraffea A.Fracturetoughness demands in welded beam-column momentconnections[J].Journal of Structural Engineering,ASCE,2000,126(1):88―97.
[6]Matos C G,Dodds R H Jr.Probabilistic modeling ofweld fracture in steel frame connections part I:quasi-static loading[J].Engineering Structures,2001,23(8):1011―1030.
[7]Matos C G,Dodds R H Jr.Probabilistic modeling ofweld fracture in steel frame connections part II:seismicloading[J].Engineering Structures,2002,24(6):687―705.
[8]Chi W M,Kanvinde A M,Deierlein G G.Prediction ofductile fracture in steel connections using SMCScriterion[J].Journal of Structural Engineering,ASCE,2006,132(2):171―181.
[9]Wu Y M,Wang Y Q,Shi Y J,et al.Effects of lowtemperature on properties of structural steels[J].Journalof University of Science and Technology Beijing,2004,11(5):442―448.
[10]李杰.地震循环载荷下钢结构梁柱焊接节点耗能与损伤行为的研究[D].天津:天津大学,2002.Li Jie.Investigation on energy dissipation andaccumulative damage of welded beam-to-columnconnection under earthquake cyclic loading[D].Tianjin:Tianjin University,2002.(in Chinese)
[11]张莉.钢结构刚性梁柱节点抗震性能的研究[D].天津:天津大学,2004.Zhang Li.Study on earthquake resistance of rigidbeam-to-column connection of steel structure[D].Tianjin:Tianjin University,2004.(in Chinese)
[12]郁有升,王燕.钢框架梁翼缘削弱型节点力学性能的试验研究[J].工程力学,2009,26(2):168―175.Yu Yousheng,Wang Yan.Experimental study on themechanical property of reduced beam sectionconnections of steel frames[J].Engineering Mechanics,2009,26(2):168―175.(in Chinese)
[13]Chen H,Shi Y J,Wang Y Q.Fracture toughness pro-perties of moment resistant column-beam connections-Part I:elastic analysis[J].International Journal of SteelStructures,2004;4(1):1―7.
[14]Chen H,Shi Y J,Wang Y Q.Fracture toughness prop-erties of moment resistant column-beam connections-Part II:inelastic analysis[J].International Journal ofSteel Structures,2004,4(1):9―14.
[15]Wang Y Q,Zhou H,Shi Y J,Chen H.Study on fracturetoughness indices of Chinese structural steel and weldmetal[C].The 20th International Offshore(Ocean)andPolar Engineering Conference,Beijing,China,June20-26,2010.
[16]ABAQUS.Analysis User’s Manual Version 6.5[M].Providence,RI:Hibbitt,Karlsson and Sorenson,Inc.,2005.
[17]Paret T F.The W1 issue I:Extent of weld fracturingduring Northridge earthquake[J].Journal of StructuralEngineering,2000,126(1):10―18.
[18]王元清,武延民,石永久,等.钢结构构件抗断裂分析理论与实用方法研究[J].湖南大学学报(自然科学版),2006,33(1):11―15.Wang Yuanqing,Wu Yanmin,Shi Yongjiu,et al.Research on the theory and design method for thefracture resistance of steel components[J].Journal ofHunan University(Natural Sciences),2006,33(1):11―15.(in Chinese)
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