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摘要：
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目前混凝土和钢筋混凝土建筑物多是以单轴强度为标准设计的,但实际上,大多数建筑物均处于多轴应力状态。文中从细观层次上分析了混凝土的内部结构,对混凝土试块在双轴应力作用下的力学特性进行了较为全面的随机骨料模型数值模拟。试验成果表明,试件的双轴强度与单轴强度相比有显著区别,而且与应力比有很大的关系,混凝土的非均质性表现的更为突出。通过模拟试件在双轴应力作用下的强度包络图可以看出,常规混凝土的薄弱环节是骨料与砂浆基质之间的粘结面,裂纹沿界面扩展并最终导致试件的破坏,这与室内实验所得结果是相似的,试件的破坏形态也基本与实验中观察到的一致。因此在结构设计中如果考虑到这些情况,则可以避免浪费材料或者受力考虑不足造成结构处于危险状态。
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At present,concretes and reinforced concretes are designed in uniaxial strength,but actually most of buildings are under biaxial stress.In this paper,the inner structure of concrete specimens is analyzed on meso-level,the mechanics charac-teristic on concrete specimen under biaxial stress can be carried out with the random aggregate structures the numerical experi-ment.The experiment result shows that biaxial strength is difference from the uniaxial strength,and related with the stress ratio,concrete heterogeneity display to emphasize.Through the strength envelope map by simulation specimens under biaxial stress,it is observed that the weak location of common concretes is the interfacial bonding between aggregate and mortar;the cracks ex-pand along the interface,lead to damage of specimen finally.It is similar to the result in the lab.The damage form of specimens is consistent with the form in the experiment.If taking these circumstances into account,it will avoid wasting materials or the structure in danger caused by lack of consideration of stress.
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基金项目：
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国家科技支撑计划项目(2008BAJ08B00)
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作者简介：
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参考文献：
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[1]Kupfer H B,Gerstle K H.Behavior of concrete under multiaxialstress[J].Journal of Engineering Mechanics Division,ASCE,1973,99(EM4):852-866.
[2]GB50010—2002,混凝土结构设计规范[S].
[3]Walraven J C,Reinhardt H W.Theory and experiments on themechanical behavior of cracks in plain and reinforced concretesubjected to shear loading[J].HERON,1991,26(1A).
[4]Schlangen E,Van Mier J G M.Lattice model for numericalsimulation of concrete fracture[C]//International Conference onDam Fracture Denver.Colorado,1991:214-231.
[5]刘光珽,王宗敏.用随机骨料模型数值模拟混凝土材料的断裂[J].清华大学学报(自然科学版),1996,36(1):84-89.
[6]过镇海,王传志.多轴应力下混凝土的强度和破坏准则研究[J].土木工程学报,1991,24(3):1-14.
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