全级配混凝土梁动强度提高机理研究
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摘要
基于细观力学方法对全级配混凝土梁的动强度提高机理进行研究.假定混凝土由骨料、砂浆和界面三相材料组成,按全级配混凝土实际配比生成随机混凝土骨料模型.采用塑性损伤模型并考虑材料的应变软化,利用全级配混凝土梁的静弯拉(破坏)试验标定骨料、砂浆和界面的参数.在此基础上对冲击荷载下全级配混凝土梁的动弯拉破坏过程进行数值模拟,重点讨论惯性效应和应变率效应对混凝土材料强度增强因子的影响.研究结果表明:(a)当应变率小于8s-1时,材料惯性对梁的极限荷载影响可以忽略不计;当应变率大于8s-1时,材料惯性对全级配混凝土强度的动力增强因子(SDIF)影响增大.(b)当应变率小于20s-1时,率效应对SDIF影响较大,在高应变率区SDIF主要受材料惯性的影响.此外,探讨了初始缺陷(损伤)对全级配混凝土梁破坏荷载的影响.
The dynamic strength enhancement mechanism of a fullygraded concrete beam was studied based on mesomechanics.Assuming that the concrete composites are composed of aggregate particles,cement matrix,and an interface transitional zone(ITZ),the numerical aggregate models were generated randomly based on the actual aggregate grade of fully-graded concrete.A plastic-damage model for concrete,in which strain softening was taken into consideration,was adopted.The material parameters of the aggregate particles,cement matrix,and ITZ were identified through a static flexural-tension experiment.Based on the identified parameters,the dynamic flexural-tension failure process of the fully-graded concrete beam was numerically simulated under an impact load.The effects of inertia and strain rate on the dynamic increase factor(SDIF) were analyzed.The results show the following:(a) The inertial effect on the limited load could be neglected when the strain rate was lower than 8 s-1;when the strain rate was greater than 8 s-1,the inertial effect on SDIF of the fully-graded concrete beam increased.(b) When the strain rate was lower than 20 s-1,the strain rate had a significant effect on SDIF,whereas the SDIF was mainly controlled by the inertia effect.In addition,the effect of initial damage on the failure load of the fully-graded concrete beam was studied.
The dynamic strength enhancement mechanism of a fullygraded concrete beam was studied based on mesomechanics.Assuming that the concrete composites are composed of aggregate particles,cement matrix,and an interface transitional zone(ITZ),the numerical aggregate models were generated randomly based on the actual aggregate grade of fully-graded concrete.A plastic-damage model for concrete,in which strain softening was taken into consideration,was adopted.The material parameters of the aggregate particles,cement matrix,and ITZ were identified through a static flexural-tension experiment.Based on the identified parameters,the dynamic flexural-tension failure process of the fully-graded concrete beam was numerically simulated under an impact load.The effects of inertia and strain rate on the dynamic increase factor(SDIF) were analyzed.The results show the following:(a) The inertial effect on the limited load could be neglected when the strain rate was lower than 8 s-1;when the strain rate was greater than 8 s-1,the inertial effect on SDIF of the fully-graded concrete beam increased.(b) When the strain rate was lower than 20 s-1,the strain rate had a significant effect on SDIF,whereas the SDIF was mainly controlled by the inertia effect.In addition,the effect of initial damage on the failure load of the fully-graded concrete beam was studied.
引文
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[9]LUBLINER J,OLIVER J,OLLERR S,et al.A plastic-damage model for concrete[J].International Journal of Solids and Structures,1989,25(3):229-326.
[10]LEE J,FENVES G L.Plastic-damage model for cyclic loading of concrete structures[J].Journal of Engineering Mechanics,1998,124(8):892-900.
[11]HILLERBORG A,MODEER M,PETERSSON P E.Analysis of crack formation and crack growth in concrete by means of fracturemechanics and finite elements[J].Cement and Concrete Research,1976,6(6):773-782.
[12]CEB-FIPModel Code 1990 Redwood Books[S].
[2]马怀发,陈厚群,黎保琨.应变率效应对混凝土动弯拉强度的影响[J].水利学报,2005,36(1):69-76.(MA Hua-i fa,CHEN Hou-qun,LI Bao-kun.Influence of strain rate effect on dynamic bending strength of concrete[J].Journal of HydraulicEngineering,2005,36(1):69-76.(in Chinese))
[3]杜修力,田瑞俊,彭一江.预静载对全级配混凝土梁动弯拉强度的影响[J].地震工程与工程振动,2009,29(2):98-102.(DU Xiu-li,TIAN Ru-i jun,PENG Y-i jiang.Influence of initial static loading on dynamical bending strength of fully-graded concretebeam[J].Journal of Earthquake Engineering and Engineering Vibration,2009,29(2):98-102.(in Chinese))
[4]王怀亮,宋玉普,王宝庭.用刚体弹簧元法研究全级配混凝土力学性能[J].大连理工大学学报,2006,46(增刊):105-117.(WANG Hua-i liang,SONG Yu-pu,WANG Bao-ting.Numerical simulation ofmechanical behavior offully-grade concrete based on rigidbody spring model[J].Journal of Dalian University ofTechnology,2006,46(Sup):105-117.(in Chinese))
[5]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 Hua-i fa,WANG L-i tao,CHEN Hou-qun,et al.Mechanism of dynamic damage delay characteristic of concrete[J].Journal ofHydraulic Engineering,2010,41(6):659-664.(in Chinese))
[6]杜成斌,江守燕,徐海荣,等.基于细观力学的湿筛混凝土试件动弯拉破坏研究[J].河海大学学报:自然科学版,2012,40(2):195-200.(DU Cheng-bin,JIANG Shou-yan,XU Ha-i rong,et al.Study on static and dynamic failure of we-t screened concretespecimen[J].Journal ofHohai University:Natural Science,2012,40(2):195-200.(in Chinese))
[7]DL/T5150—2001水工混凝土试验规程[S].
[8]杜成斌,孙立国.任意形状混凝土骨料的数值模拟及其应用[J].水利学报,2006,37(6):662-667.(DU Cheng-bin,SUN L-iguo.Numerical simulation of concrete aggregates with arbitrary shapes and its application[J].Journal ofHydraulic Engineering,2006,37(6):662-667.(in Chinese))
[9]LUBLINER J,OLIVER J,OLLERR S,et al.A plastic-damage model for concrete[J].International Journal of Solids and Structures,1989,25(3):229-326.
[10]LEE J,FENVES G L.Plastic-damage model for cyclic loading of concrete structures[J].Journal of Engineering Mechanics,1998,124(8):892-900.
[11]HILLERBORG A,MODEER M,PETERSSON P E.Analysis of crack formation and crack growth in concrete by means of fracturemechanics and finite elements[J].Cement and Concrete Research,1976,6(6):773-782.
[12]CEB-FIPModel Code 1990 Redwood Books[S].
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