混凝土细观结构动态力学特性CT试验研究
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摘要
混凝土材料在动载作用下具有与静载不同的特性。从实时CT扫描试验出发,以素混凝土圆柱体试样为研究对象,分析了正弦波动压和动拉荷载作用下,混凝土的细观结构变化对动态力学特性中诸如强度、变形和破损形态的影响。通过CT差值图像研究,得出动压荷载作用下混凝土裂纹具有发展迅速,破坏过程短,破坏裂纹多,破坏面积大等特点;通过CT数等密度分割图研究,得出动拉荷载作用下混凝土微裂纹突然合并形成一条主裂纹贯穿试件,试件突然断裂;通过加载过程中CT数变化规律研究,得出动压荷载作用下混凝土的密度经历了一个先增大后减小的过程,试件经历了压密、扩容、裂纹贯通直至最后破坏的过程,而动拉荷载后试件的密度持续减小直至断裂,荷载初期无压密现象。混凝土试件形成单位面积的压、拉裂纹面所需的能量基本相同,形成单位面积的动力裂纹面所需的能量略大于静力裂纹面所需能量。混凝土动压、动拉的应力状态不同,导致其破坏程度不同,所形成的裂纹面积不同,所需的总能量也不同,最终导致测定的强度不同,应力状态不同是动压、动拉强度差异的根本原因。
Concrete material under dynamic loads has different characteristics comparing with those under static loads. Here,CT tests of concrete material were investigated taking,plain concrete specimens under dynamic loading as study objects. The effects of concrete meso structure change on its dynamic characteristics,such as,strength,deformation and damage morphology under the sine wave dynamic pressure and dynamic tensile load were analyzed. Through studying CT difference images,it was shown that cracks in concrete under compressive loads grow rapidly,their failure process is short,failure cracks have many,damage area is large,etc. Through CT number equidensity segmentation image study,it was shown that under dynamic tensile loading,concrete micro cracks suddenly merge to form a main crack passing through the specimen,the specimen breaks suddenly. Through studying the CT number change law in loading process it was shown that the concrete density decreases after a first increase under the dynamic compressive loads,specimens experience a process of compaction,expansion,crack coalescence until final failure,and under the dynamic tensile load the specimen density continuously drops until its fracture,early without compaction; different stress states of concrete under dynamic compressive loads and dynamic tensile loads lead to its different damage levels,different crack areas formed,different total energy required,and its different strengths neasured finally; different stress states are the essential cause to cause the difference between dynamic tensile strength and dynamic compression one.
Concrete material under dynamic loads has different characteristics comparing with those under static loads. Here,CT tests of concrete material were investigated taking,plain concrete specimens under dynamic loading as study objects. The effects of concrete meso structure change on its dynamic characteristics,such as,strength,deformation and damage morphology under the sine wave dynamic pressure and dynamic tensile load were analyzed. Through studying CT difference images,it was shown that cracks in concrete under compressive loads grow rapidly,their failure process is short,failure cracks have many,damage area is large,etc. Through CT number equidensity segmentation image study,it was shown that under dynamic tensile loading,concrete micro cracks suddenly merge to form a main crack passing through the specimen,the specimen breaks suddenly. Through studying the CT number change law in loading process it was shown that the concrete density decreases after a first increase under the dynamic compressive loads,specimens experience a process of compaction,expansion,crack coalescence until final failure,and under the dynamic tensile load the specimen density continuously drops until its fracture,early without compaction; different stress states of concrete under dynamic compressive loads and dynamic tensile loads lead to its different damage levels,different crack areas formed,different total energy required,and its different strengths neasured finally; different stress states are the essential cause to cause the difference between dynamic tensile strength and dynamic compression one.
引文
[1]陈厚群,吴胜兴,党发宁著.高拱坝抗震安全[M].北京:中国电力出版社,2012.
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[3]王海龙,李庆斌.不同加载速率下干燥与饱和混凝土抗压性能试验研究分析[J].水力发电学报,2007,26(1):84-89.WANG Hai-long,LI Qing-bin.Experiments of the compressive properties of dry and saturated concrete under different loading rates[J].Journal of Hydroelectric Engineering,2007,26(1):84-89.
[4]肖诗云,张剑.荷载历史对混凝土动态受压损伤特性影响试验研究[J].水利学报,2010,41(8):943-952.XIAO Shi-yun,ZHANG Jian.Experiment study on effect of load histories on dynamic compressive damage behaviors of concrete[J].Journal of Hydraulic Engineering,2010,41(8):943-952.
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[9]李庆斌,郑丹.混凝土动力强度提高的机理探讨[J].工程力学,2005,22(s):188-193.LI Qing-bin,ZHENG Dan.Micro-mechanism on the enhancement of dynamic strength for concrete[J].Engineering Mechanics,2005,22(s):188-193.
[10]Bischoff P H,Perry S H.Comparessive behaviour of concrete at high strain rates[J].Materials and Structures,1991,24:425-450.
[11]闫东明,林皋,徐平.三向应力状态下混凝土动态强度和变形特性研究[J].工程力学,2007,24(3):58-64.YAN Dong-ming,LIN Gao,XU Ping.Dynamic strength and deformation of concrete in triaxial stress states[J].Engineering Mechanics,2007,24(3):58-64.
[12]Buyukozturk O.Imaging of concrete structures[J].NDT&E International,1998,31(4):233-243.
[13]陈厚群,丁卫华,蒲毅彬,等.单轴压缩条件下混凝土细观破裂过程的X射线CT实时观测[J].水利学报,2006,37(9):1044-1050.CHEN Hou-qun,DING Wei-hua,PU Yi-bing,et al.Real time observation on meso fracture process of concrete using Xray CT under uniaxial compressive condition[J].Journal of Hydraulic Engineering,2006,37(9):1044-1050.
[14]党发宁,刘彦文,丁卫华,等.基于破损演化理论的混凝土CT图像定量分析[J].岩石力学与工程学报,2007,26(8):1588-1594.DANG Fa-ning,LIU Yan-wen,DING Wei-hua,et al.Quantitative analysis of concrete CT images based on damage fracture evolution theory[J].Chinese Journal of Rock Mechanics and Engineering,2007,26(8):1588-1594.
[15]田威,党发宁,丁卫华,等,适于CT试验的动态加载设备研制及其应用[J].岩土力学,2010,31(1):309-313.TIAN Wei,DANG Fa-ning,DING Wei-hua,et al.Development of a dynamic loading apparatus for CT experiment and its application[J],Rock and soil Mechanics,2010,31(1):309-313.
[16]田威,党发宁,陈厚群.动力荷载作用下混凝土破裂特征的CT试验研究[J].地震工程与工程振动,2011,31(1):30-34.TIAN Wei,DANG Fa-ning,CHEN Hou-qun.CT experimental study on failure characteristics of concrete under dynamic loading[J].Journal of Earthquake Engineering and Engineering Vibration,2011,31(1):30-34.
[17]梁昕宇.基于最小能量原理混凝土强度细观力学研究[D].西安:西安理工大学,2013.
[2]马怀发著.全级配大坝混凝土动态损伤破坏机理研究及其细观力学分析方法[M].北京:中国水利水电出版社,2008.
[3]王海龙,李庆斌.不同加载速率下干燥与饱和混凝土抗压性能试验研究分析[J].水力发电学报,2007,26(1):84-89.WANG Hai-long,LI Qing-bin.Experiments of the compressive properties of dry and saturated concrete under different loading rates[J].Journal of Hydroelectric Engineering,2007,26(1):84-89.
[4]肖诗云,张剑.荷载历史对混凝土动态受压损伤特性影响试验研究[J].水利学报,2010,41(8):943-952.XIAO Shi-yun,ZHANG Jian.Experiment study on effect of load histories on dynamic compressive damage behaviors of concrete[J].Journal of Hydraulic Engineering,2010,41(8):943-952.
[5]吴胜兴,周继凯,陈厚群.基于微观结构特征的混凝土动态抗拉强度提高机理及其统一模型[J].水利学报,2010,41(4):419-428.WU Sheng-xing,ZHOU Ji-kai,CHEN Hou-qun.Unified model and mechanism for dynamic tensile strength increase of concrete base on its microstructure characteristics[J].Journal of Hydraulic Engineering,2010,41(4):419-428.
[6]马怀发,王立涛,陈厚群,等.混凝土动态损伤的滞后特性[J].水利学报,2010,41(6):659-664.MA Huai-fa,WANG Li-tao,CHEN Hou-qun,et al.Mechanism of dynamic damage delay characteristic of concrete[J].Journal of Hydraulic Engineering,2010,41(6):659-664.
[7]Harris D W,Mohorovic C E,Dolen T P.Dynamic properties of mass concrete obtained from dam cores[J].ACI Material Journal,2000(97):290-296.
[8]刘传雄,李玉龙,吴子燕,等.混凝土材料的动态压缩破坏机理及本构关系[J].振动与冲击,2011,30(5):1-5.LIU Chuan-xiong,LI Yu-long,WU Zi-yan,et al.Failure mechanism and constitutive model of a concrete material under dynamic compressive oads[J].Journal of Vibration and Shock,2011,30(5):1-5.
[9]李庆斌,郑丹.混凝土动力强度提高的机理探讨[J].工程力学,2005,22(s):188-193.LI Qing-bin,ZHENG Dan.Micro-mechanism on the enhancement of dynamic strength for concrete[J].Engineering Mechanics,2005,22(s):188-193.
[10]Bischoff P H,Perry S H.Comparessive behaviour of concrete at high strain rates[J].Materials and Structures,1991,24:425-450.
[11]闫东明,林皋,徐平.三向应力状态下混凝土动态强度和变形特性研究[J].工程力学,2007,24(3):58-64.YAN Dong-ming,LIN Gao,XU Ping.Dynamic strength and deformation of concrete in triaxial stress states[J].Engineering Mechanics,2007,24(3):58-64.
[12]Buyukozturk O.Imaging of concrete structures[J].NDT&E International,1998,31(4):233-243.
[13]陈厚群,丁卫华,蒲毅彬,等.单轴压缩条件下混凝土细观破裂过程的X射线CT实时观测[J].水利学报,2006,37(9):1044-1050.CHEN Hou-qun,DING Wei-hua,PU Yi-bing,et al.Real time observation on meso fracture process of concrete using Xray CT under uniaxial compressive condition[J].Journal of Hydraulic Engineering,2006,37(9):1044-1050.
[14]党发宁,刘彦文,丁卫华,等.基于破损演化理论的混凝土CT图像定量分析[J].岩石力学与工程学报,2007,26(8):1588-1594.DANG Fa-ning,LIU Yan-wen,DING Wei-hua,et al.Quantitative analysis of concrete CT images based on damage fracture evolution theory[J].Chinese Journal of Rock Mechanics and Engineering,2007,26(8):1588-1594.
[15]田威,党发宁,丁卫华,等,适于CT试验的动态加载设备研制及其应用[J].岩土力学,2010,31(1):309-313.TIAN Wei,DANG Fa-ning,DING Wei-hua,et al.Development of a dynamic loading apparatus for CT experiment and its application[J],Rock and soil Mechanics,2010,31(1):309-313.
[16]田威,党发宁,陈厚群.动力荷载作用下混凝土破裂特征的CT试验研究[J].地震工程与工程振动,2011,31(1):30-34.TIAN Wei,DANG Fa-ning,CHEN Hou-qun.CT experimental study on failure characteristics of concrete under dynamic loading[J].Journal of Earthquake Engineering and Engineering Vibration,2011,31(1):30-34.
[17]梁昕宇.基于最小能量原理混凝土强度细观力学研究[D].西安:西安理工大学,2013.
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