高温后混凝土软化本构曲线的确定
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摘要
结合高温后混凝土楔入劈拉法试验,采用3种常温下混凝土双线性软化本构曲线,借鉴常温下双K断裂模型中失稳韧度KIC,un,T与黏聚韧度KIC,c,T,起裂韧度KIC,ini,T间的定量关系,对高温后混凝土断裂韧度间的关系进行研究.结果表明:高温后黏聚韧度KIC,c,T的计算分为2种情况,用不同软化曲线计算得到的黏聚韧度值相近;由3种常温下的软化曲线计算得到的失稳断裂韧度值与实测失稳断裂韧度值能够较好吻合,现有软化曲线能较好地反映高温后混凝土断裂性能;同时验证了双K断裂模型对高温后混凝土的适用性.
Wedge-splitting tests of the concrete specimens after exposure to high temperature were conducted.Adopting three bilinear softening curves at room temperature and taking account of the quantitative relationship among unstable fracture toughness KIC,un,T,initial fracture toughness KIC,ini,T and cohesive fracture toughness KIC,c,T from the double-Kfracture model,the relationship of these three parameters for the concrete after exposure to high temperature was investigated.There are two cases of calculation of cohesive fracture toughness KIC,c,T,and the similar values of KIC,c,T are obtained from the calculation using different softening curves.The calculated unstable fracture toughness KIC,un,T based on the three softening curves has a good coincidence with the experimental value,which shows that the softening curves could well reflect the real fracture feature of the concrete after exposure to high temperature and the adaptability of application of double-Kfracture model to the concrete after exposure to high temperature is proved.
Wedge-splitting tests of the concrete specimens after exposure to high temperature were conducted.Adopting three bilinear softening curves at room temperature and taking account of the quantitative relationship among unstable fracture toughness KIC,un,T,initial fracture toughness KIC,ini,T and cohesive fracture toughness KIC,c,T from the double-Kfracture model,the relationship of these three parameters for the concrete after exposure to high temperature was investigated.There are two cases of calculation of cohesive fracture toughness KIC,c,T,and the similar values of KIC,c,T are obtained from the calculation using different softening curves.The calculated unstable fracture toughness KIC,un,T based on the three softening curves has a good coincidence with the experimental value,which shows that the softening curves could well reflect the real fracture feature of the concrete after exposure to high temperature and the adaptability of application of double-Kfracture model to the concrete after exposure to high temperature is proved.
引文
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[4]GOPALARATNAM V S,SHAH S P.Softening response of plain concrete in direct tension[J].ACI Journal,1985,82(3):310-323.
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[9]PROKOPSKI G.Fracture toughness of concretes at high temperature[J].Journal of Materials Science,1995,30(6):1609-1612.
[10]ABDEL-FATTAH H,HAMOUSH S A.Variation of the fracture toughness of concrete with temperature[J].Construction and Building Materials,1997,11(2):105-108.
[11]余江滔.火灾后混凝土构件损伤评估的试验及理论研究[D].上海:同济大学,2007.YU Jiang-tao.Experimental and theoretical research on damage assessment of reinforced concrete member after fire[D].Shanghai:Tongji University,2007.(in Chinese)
[12]XU S L,REINHART H W.Determination of double-K criterion for crack propagation in quasi-brittle fracture(PartⅢ):Compact tension specimens and wedge splitting specimens[J].International Journal of Fracture,1999,98(2):179-193.
[13]中国航空研究院.应力强度因子手册[M].北京:科学出版社,1981:151.Aviation Institute of China.Stress intensity factor handbook[M].Beijing:Science Press,1981:151.(in Chinese)
[14]JENQ Y S,SHAH S P.Two parameter fracture model for concrete[J].Journal of Engineering Mechanics,1985,111(10):1227-1241.
[2]CEB-Comite Euro-international du Beton CEB-FIP model code 1990,Bulletin Dinformation,No.213/214[S].
[3]XU S L,REINHART H W.Determination of double-K criterion for crack propagation in quasi-brittle fracture(PartⅡ):Analytical evaluating and practical measuring methods for three-point bending notched beam[J].International Journal of Fracture,1999,98(2):151-177.
[4]GOPALARATNAM V S,SHAH S P.Softening response of plain concrete in direct tension[J].ACI Journal,1985,82(3):310-323.
[5]REINHART H W,CORNELISSEN H A W,HORDIJK D A.Tensile tests and failure analysis of concrete[J].Journal of Structure Engineering,1986,112(11):2461-2477.
[6]BAKER G.The effect of exposure to elevated temperatures on the fracture energy of plain concrete[J].RILEM Materials and Structures,1996,29(6):383-388.
[7]ZHANG B,BICANIC N,PEARCEC J,et al.Residual fracture properties of normal and high-strength concrete subject to elevated temperatures[J].Magazine of Concrete Research,2000,52(2):123-136.
[8]NIELSEN C V,BICANIC N.Residual fracture energy of high-performance and normal concrete subject to high temperatures[J].RILEM Materials and Structures,2003,36(8):515-521.
[9]PROKOPSKI G.Fracture toughness of concretes at high temperature[J].Journal of Materials Science,1995,30(6):1609-1612.
[10]ABDEL-FATTAH H,HAMOUSH S A.Variation of the fracture toughness of concrete with temperature[J].Construction and Building Materials,1997,11(2):105-108.
[11]余江滔.火灾后混凝土构件损伤评估的试验及理论研究[D].上海:同济大学,2007.YU Jiang-tao.Experimental and theoretical research on damage assessment of reinforced concrete member after fire[D].Shanghai:Tongji University,2007.(in Chinese)
[12]XU S L,REINHART H W.Determination of double-K criterion for crack propagation in quasi-brittle fracture(PartⅢ):Compact tension specimens and wedge splitting specimens[J].International Journal of Fracture,1999,98(2):179-193.
[13]中国航空研究院.应力强度因子手册[M].北京:科学出版社,1981:151.Aviation Institute of China.Stress intensity factor handbook[M].Beijing:Science Press,1981:151.(in Chinese)
[14]JENQ Y S,SHAH S P.Two parameter fracture model for concrete[J].Journal of Engineering Mechanics,1985,111(10):1227-1241.