A Research on the Macroscopic and Mesoscopic Parameters of Concrete Based on an Experimental Design Method.

Hui Su,Baowen Hu,Hongliang Li,Jiaqi Yang

doi:10.3390/ma14071627

Hui Su, Baowen Hu + Show 2 more

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https://doi.org/10.3390/ma14071627

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Abstract

Concrete is a composite material that has complex mechanical properties. The mechanical properties of each of its components are different at the mesoscopic scale. Studying the relationship between the macroscopic and mesoscopic parameters of concrete can help better understand its mechanical properties at these levels. When using the discrete element method to model the macro-mesoscopic parameters of concrete, their calibration is the first challenge. This paper proposes a numerical model of concrete using the particle discrete element software particle flow code (PFC). The mesoscopic parameters required by the model need to be set within a certain range for an orthogonal experimental design. We used the proposed model to perform numerical simulations as well as response surface design and analysis. This involved fitting a set of mapping relationships between the macro–micro parameters of concrete. An optimization model was established in the MATLAB environment. The program used to calibrate the mesoscopic parameters of concrete was written using the genetic algorithm, and its macro-micro parameters were inverted. The following three conclusions can be drawn from the orthogonal test: First, the tensile strength and shear strength of the parallel bond between the particles of mortar had a significant influence on the peak compressive strength of concrete, whereas the influence of the other parameters was not significant. Second, the elastic modulus of the parallel bonding between particles of mortar, their stiffness ratio and friction coefficient, and the elastic modulus and stiffness ratio of contact bonding in the interfacial transition zone had a significant influence on the elastic modulus, whereas the influence of the other parameters was not significant. Third, the elastic modulus, stiffness ratio, and friction coefficient of the particles of mortar as well as the ratio of the contact adhesive stiffness in their interfacial transition zone had a significant influence on Poisson’s ratio, whereas the influence of the other parameters was not significant. The fitting effect of the response surface design was good.

Highlights

IntroductionNo unified method is available to describe the macroscopic parameters of particles of geotechnical materials by using their microscopic parameters
This paper proposes a discrete element method (DEM) based on the discrete element software PFC2D
The results show that σc and τ c had a significant influence on σu because their sizes determined the difficulty of relative sliding between particles after bond failure

Summary

Introduction

No unified method is available to describe the macroscopic parameters of particles of geotechnical materials by using their microscopic parameters. Laboratory experiments are a feasible approach, they have such problems as low efficiency, high cost, and a large dispersion in the results. Cundall established the discrete element method (DEM) to solve this problem [1]. The DEM is a numerical method to examine the mechanics of discontinuous media based on Newton’s second law of motion. It represents the given geotechnical material as a rigid particle model in which its mesoscopic and macroscopic parameters can be related. It is directly related to the geometrical characteristics of the assignment particles and particle contact between mesoscopic mechanics parameters of the

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