Concrete is a predominant construction material due to several advantages; however, the pure cementitious composites have shown quasi-brittle behavior with undesirable typical large cracks under tensile loading conditions. Thus, the addition of a small volume of short fibers is a well-known strategy to increase the ductility and toughness of cementitious matrices besides optimization of the crack opening. Strain-hardening cement-based composites (SHCCs) is a particular class of fiber-reinforced concretes (FRCC) that can develop controlled multiple cracks while subjected to incremental tensile loading conditions. However, a proper composition design, especially concerning fiber and bond properties, still follows a trial and error approach.
This work presents a newly developed model to simulate SHCC at the meso-scale level. This model is based on Finite-Element-Method and allows for nonlinear behavior for cement matrix, fiber material, and bond laws. Concerning three complexities of target FRCC, i.e., crack formation in the cement matrix, a large number of explicit fibers with arbitrary random distribution, and fibers’ interaction with the cement matrix via the bond, extra features are added to standard FE consist of:
• Further development of the Strong Discontinuity Approach (SDA) to model discrete cracking of continuum elements on the element level
• Discretization of single fibers by truss elements with truss nodes independently placed of continuum nodes
• Connecting SDA elements to explicit truss elements by particular bond elements.
In this research study, first, theoretical basics and special implementation issues were described. Later, this newly developed model was calibrated with several simple configurations. The bond law utilized in the simulation was derived from single fiber pullout test and calibrated with several analyses. In the next step, 2D SHCC dumbbell specimens under tensile loading condition were simulated, and a series of numerical case studies were performed to assess the quality, credibility, and limitations of the numerical model. It should be noted that cracking patterns could not be directly compared to experimental cracking patterns as the simulation model’s current state is deterministic by random material properties that influence the experimental specimen behavior. Taking the effect of random field and other simplifying assumptions into account, the simulation model seems to describe enumerated SHCC behavior at an acceptable level.
In summary, a further base is given for the target-oriented design of FRCC material composition to reach the given objectives of material properties. The concepts and methods presented in this study can simulate short and thin polymer fibers in a random position and steel fibers and structures with long reinforcement in a regular arrangement.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:74170 |
| Date | 15 March 2021 |
| Creators | Shehni, Alaleh |
| Contributors | Häussler-Combe, Ulrich, Di Prisco, Marco, Scheffler, Christina, Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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