Abstract
The present paper shows the results of three-dimensional (3D) meso-scale numerical simulations that were performed on unconfined and Carbon Fibre Reinforced Polymer (CFRP)-confined concrete specimens under uniaxial compression. The numerical results are compared with available experimental data. The meso-scale structure of concrete is composed by two phases, namely: the coarse aggregate and the mortar matrix. The presence of Interfacial Transition Zone (ITZ) is neglected. A simple generation procedure is used to randomly place the coarse aggregate inside the concrete specimens. The finite element code MASA is used to perform the three-dimensional (3D) Finite Element meso-scale simulations. The constitutive laws for mortar and epoxy resin are based on the microplane model, while an elastic-brittle behavior is assumed for the fibers. Aggregate in concrete is considered to be linear elastic. The adopted meso-scale model for concrete can realistically reproduce the mechanical behavior of both unconfined and CFRP-confined specimens. However, in the case of small corner radius, the effect of confinement predicted by the model is overestimated with respect to the experimental results. This is partially related to the simplifications introduced in the model in terms of aggregate volumetric fraction (10%) and aggregate size distribution. It is shown that a more detailed meso-scale model, which is characterized by 30% of the coarse aggregate and realistic aggregate size distribution, can better capture the interaction between the concrete heterogeneity and the confining effect provided by CFRP.
Highlights
The use of composites, such as Carbon Fibre Reinforced Polymer (CFRP), as external strengthening material for concrete and reinforced concrete (RC) structural elements, is becoming very popular.The main reason is the improved performance of the retrofitted members, in terms of enhanced strength and ductility
The present study focuses on the application of CFRP as confining material for relatively small concrete columns subjected to uniaxial compressive load where the specimens are fully wrapped along the entire height
The general trend of the trend of the numerical curves confirms the experimental evidences, i.e. the confining effect numerical curves confirms the experimental evidences, i.e. the confining effect provided by CFRP
Summary
The use of composites, such as Carbon Fibre Reinforced Polymer (CFRP), as external strengthening material for concrete and reinforced concrete (RC) structural elements, is becoming very popular.The main reason is the improved performance of the retrofitted members, in terms of enhanced strength and ductility. CFRP is frequently used for confining of compressed concrete columns, and for shear [1,2,3] and bending [4,5] strengthening of flexural elements, e.g. beams. The shear strengthening with externally bonded CFRP sheets and laminates is one common application for reinforced concrete beams. The presence of the slab can prevent the full wrapping and/or the sufficient end anchorage of the externally bonded material [1]. In such cases, the bond performance of the interface between concrete and CFRP is fundamental for preventing a premature de-bonding, i.e. brittle failure of the strengthened element
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