PARAMETRIC INVESTIGATIONS AND THE DEVELOPMENT OF MESOSCALE MODELLING APPROACHES FOR CONCRETE

  • Jiaming Wang

Student thesis: Phd

Abstract

Concrete, as the most widely used construction material, has been applied in a variety of engineering structures. To fully understand the mechanisms of macroscopic behaviour and improve concrete design, it is important to carry out numerical modelling of concrete under complex loadings. The highly heterogeneous composition of concrete needs to be considered in order to better understand its mechanical response and damage evolution at macro-scale. A novel computational technology, which models the damage and failure of quasi-brittle materials, e.g. concrete, at meso-scale provides a powerful tool to realistically predict the mechanical behaviour and failure of concrete. The concrete meso-structure includes coarse aggregates, mortar with small sand and aggregates embedded, the interfacial transition zones (ITZ) and air voids. Therefore, the main target of this thesis is to develop an effective and efficient mesoscale modelling framework to represent the constituents of concrete realistically and to better describe the damage and failure process of concrete. Three-dimensional concrete meso-structures with varied shape, size and phase particle size distribution, either generated synthetically or obtained from X-ray Computed Tomography (XCT) scanning, can be meshed in the same image-based modelling approach, which makes it efficient for concrete meso-structure generation. To compare concrete meso-structures with physically realistic and randomly prescribed aggregates and voids, both image-based and parametric (or synthetic) models are generated. They yield mechanical behaviour in good agreement with experimental data only except that the distribution of damage differs between the two models. Concrete models with various representations of ITZ are investigated and compared with experimental data. The combined modelling considering damage-plasticity model for mortar and cohesive zone model for ITZ, whose material properties are calibrated from experiment, is demonstrated to be efficient and reliable. To better understand the effect of ITZ cohesive parameters and clarify the argument on ratio of shear to normal cohesive strength and fracture energy, parametric study is carried out for meso-scale concrete models subject to various loadings. Mortar plasticity and damage dominate the overall energy dissipation, which is linked to stress-strain curve and crack pattern. Localisation of damage in both tension and compression is governed by mortar damage dissipation and concentrated by the presence of ITZ.
Date of Award31 Dec 2020
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorDirk Engelberg (Supervisor), Qing Li (Supervisor) & Andrey Jivkov (Supervisor)

Keywords

  • mesoscale concrete
  • cohesive zone model
  • concrete damage plasticity
  • finite element method

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