Concrete Mesoscopic Model Considering The Quadratic Weibull Distribution Of Material Properties

Concrete is a complex mixture composed of multiple components.Macroscopic experiments are used to study its mechanical properties,which consumes a lot of manpower and material resources.Therefore,in recent years,a method of establishing a mesoscopic concrete model to simulate its mechanical properties has emerged.The meso-level model can simulate the initiation,development and even the whole process of cracks when concrete is destroyed from the meso-level,which is of great significance.In most mesoscopic models,the consideration of the random distribution of the material parameters of each phase material is mostly based on the unit,ignoring the difference in material properties between individuals,which makes the model results deviate from the experimental phenomenon.Therefore,this article compares the traditional concrete The mesoscopic model has been improved,and a concrete mesoscopic model considering the secondary random distribution of material properties is proposed.The main results of the thesis are as follows:(1)The establishment process of the improved mesoscopic model is introduced.First,the size of the representative volume unit of the model is determined,and then the random aggregate is put in.The most suitable aggregate and mortar constitutive are selected according to the research focus of this article.The combination of traversal method and interval method realizes the individual random distribution of aggregate material properties and the secondary random distribution of ITZ layer material properties.(2)The improved model and the traditional homogeneous model were established respectively.After comparing the results of the two,it is found that the load-displacement curves of the two are basically the same,but the failure modes are different.In addition to the damage of the innermost ITZ layer of the improved model,part of the outer ITZ layer was damaged at the same time,that is,the improved model can better reflect the heterogeneous characteristics of the material than the traditional model.(3)The influence of each element of the improved model on the model result is studied.The study found that the combination of the layered treatment of the ITZ layer and the secondary random distribution of material properties can better simulate the failure process of concrete.The larger the volume fraction of aggregate,the faster the start and development of concrete damage,resulting in a decrease in the strength of concrete;the larger the proportion of coarse aggregates with large particle sizes in the model,the lower the strength of the model,but a good gradation can Improve the strength of concrete.Although the strength of mortar cannot determine the initial stage of concrete damage,it determines the final stage of concrete damage.Its strength directly determines the strength of the model;the lower the ITZ layer strength,the lower the strength of the concrete;the random distribution parameters of the model The smaller the value,the greater the degree of dispersion of material properties in the model,and the lower the strength of the model.When the parameter increases to a certain value,the model result is more stable.