Understanding the Improved Structural Behaviour of Confined Concrete

PhD defence, Friday 17 November 2017, Lise Kjær Andersen.

2017.11.17 | Trine Berndt Turtiainen Scheelke

Lise Kjær Andersen

Principal drawing of the proposed sub-macroscopic model of compressive failure of actively confined concrete: An idealised concrete cross section is shown, consisting of circular aggregate particles embedded in hardened cement paste. The prism is subjected to a vertical load and supported by an external lateral compressive stress (active confinement). By searching for the critical/weakest path of failure line through the cross section (consisting of two different parts: (i) straight failure lines through bulk cement paste and (ii) interface cracks along the perimeter of hard aggregate particles encountered), the capacity of the structure is determined as the load which will cause this failure mode to initiate.

Two highly important properties of concrete structures are the compressive strength and the ability of the structure to deform without breaking. Both properties are known to be significantly improved if a concrete structure is confined. Confinement covers two fundamentally different types of lateral support: active (external pressure) and passive (reinforcing arrangement). Seeking to better understand the material behaviour of both actively and passively confined concrete, a sub-macroscopic mechanical model of the compressive failure of confined concrete is proposed. The model combines the theory of plasticity with existing knowledge of the heterogeneity of the concrete material, assuming concrete as a two phase material of hard spherical aggregate particles embedded in a softer matrix of hardened cement paste. The proposed model allows for a solid qualitative investigation of how the concrete mix design affects the strength and the compressive failure process of both actively and passively confined concrete.

The PhD degree was completed at the Department of Engineering, Science and Technology, Aarhus University.

This résumé was prepared by the PhD student.

Time: Friday 17 November 2017 at 11.00
Place: Building 3210 (Navitas), room  05.060, Department of Engineering, Aarhus University
Title of dissertation: Strength of Confined Concrete – Applying Theory of Plasticity including Sub-Macroscopic Composite Structure of Concrete
Contact information: Lise Kjær Andersen, e-mail: lian@eng.au.dk, tel.: +45 61 76 30 05
Members of the assessment committee:
Professor Aurelio Muttoni, Head of the Structural Concrete Laboratory, École Polytechnique Fédérale de Lausanne, Switzerland
Associate Professor Gregor Fischer, Department of Civil Engineering, Technical University of Denmark
Associate Professor Steffen Petersen, Department of Engineering, Aarhus University (chair)
Main supervisor:
Professor Lars German Hagsten, Department of Engineering, Aarhus University
Co-supervisor:
Professor Rune Brincker, Department of Civil Engineering, Technical University of Denmark
Language: The PhD dissertation will be defended in English

The defence is public.
The dissertation is available for reading at the Graduate School of Science and Technology/GSST,
Ny Munkegade 120, building 1520, rooms 128-134, 8000 Aarhus C.

PhD defence
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Revised 23.11.2017