Application Research On Statistical Damage Model Of Concrete

Concrete is one of the largest and most versatile building materials in the world today,and it is closely related to our lives.Therefore,how to accurately describe the deformation and failure of concrete materials is particularly important.Compared with the wide application background of concrete,the research on the constitutive relationship of concrete lags behind the needs of engineering development.Therefore,it is imperative to establish the constitutive model of concrete and reveal the damage and failure mechanism of concrete.Based on statistical damage theory,the statistical damage constitutive model of concrete is studied in this paper.The contents are as follows:(1)Statistical damage constitutive model of concrete under uniaxial tension and uniaxial compression considering the influence of strength grade is established.Different mix ratios of concrete with different strength grades lead to obvious differences in the mechanical properties of concrete microstructures,the morphology of crack initiation and propagation and the cumulative evolution of damage during loading.The above effects can be characterized by the characteristic parameters in the model.The constitutive model is used to fit the uniaxial tension stress-strain curves of concrete with strength grade C15-C40 and strength grade C20—C80 in the Code for Design of Concrete Structures(GB50010-2010).The meso-damage evolution mechanism of deterioration of concrete with different strength grades under uniaxial tension and uniaxial compression is discussed.The intrinsic relationship between macroscopic non-linear mechanical behavior.The results show that there are significant differences in the cumulative evolution of meso-damage of concrete with different strength grades during uniaxial tension and uniaxial compression,and with the increase of concrete strength grade,its characteristic parameters show obvious regular changes.(2)Based on the statistical damage theory,the statistical damage model for concrete under uniaxial compression is proposed,which considers the impact of high temperature.The effect of high temperature changes the component and mechanical characteristics in microstructure of concrete,and then changes the initation and propagation process of micro-crack.The analysis results show that with the increase of temperature,the mechanical characteristics in micro structure and the meso-damage cumulative evolution process of concrete would be significantly changed under uniaxial compression,eventually causes concrete to show the macro-mechanical phenomenon of "weakening".The high temperature environment is divided into two sections:low-middle temperature zone(100?—400?)and high temperature zone(400?—800?),in which the degradation is dominated by different physical and chemical reactions.The different evolution law of meso-damage could be reflected by the characteristic parameters in damage model.(3)Based on the concrete orthotropic statistical damage model established by Weifeng Bai,the secondary development was carried out in the large-scale finite element calculation software ANSYS,and the whole deformation and failure process of concrete materials was refined and numerically simulated.The uniaxial tensile test and the uniaxial compression test of the concrete cube test block were simulated,and the whole process of the three-point bending beam of the concrete with different initial crack lengths from the initial loading to the final instability failure was simulated.The expansion mechanism of cracks in concrete three-point bending beams.The results show that the numerical simulation results are in good agreement with the double K fracture criterion test results and the virtual crack model test results,and the validity of the model is verified.