Damage Processes in Ultra-High Performance Fiber-Reinforced Concrete Under Cyclic Tensile Loading



Projekt description

The currently used ultra-high strength fibre-reinforced concretes (UHPFRC) usually have very high fibre contents to counteract failure with brittle fracture. Under tensile loading, the high fibre addition leads to a supercritical tensile load-bearing behaviour with high post-cracking tensile strength, which has a significant influence on the load-bearing and deformation behaviour of UHPFRC components under bending, shear force and torsion. UHPFRC is preferably used for slender and thin-walled as well as weight- and performance-optimised components due to the very high strengths that can be achieved compared to normal concrete, which are, however, particularly susceptible to vibration due to their high slenderness. It is unclear to what extent cyclic stresses affect the fibre load-bearing capacity or the post-cracking tensile strength. The degradation behaviour of UHPFRC under fatigue loading is only rudimentarily understood due to the few existing investigations. Therefore, the course of damage and the damage mechanisms of UHPFRC under cyclic tensile loading are to be fundamentally investigated experimentally and numerically in the proposed research project. On the one hand, systematically graded experimental investigations are to be carried out on small-format specimens, such as fibre tensile tests, fibre pull-out tests and UHPFRC tensile tests. The tests will be evaluated, analysed and documented with the aid of mechanical measuring procedures and imaging methods, such as digital microscopy (DM), scanning electron microscopy (SEM), computer tomography (CT) and photogrammetric measuring systems (GOM). On the other hand, the stress-deformation behaviour of UHPFRC is to be modelled mathematically-numerically consistently on the mesoscale. Continuum mechanical models with consideration of inelastic deformation behaviour and damage will be extended for the description of the material behaviour of the individual components under fatigue loading. The composite behaviour of fibre and concrete matrix is to be considered discretely in finite element analyses with the help of a composite model that is to be further developed.

The aim of the research project is to record, describe and model the degradation behaviour of fibre-reinforced ultra-high performance concrete under cyclic tensile loading with consistent attention to damage development and mechanisms on the micro and meso scales.

Publications of the project

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