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Propagation of cracks in reinforced concrete beams cracked and repaired by composite materials

Benarbia D., Benguediab M.

Mechanics and Mechanical Engineering

2017

Vol. 21, nr 3

591--601

Strengthening and repairing existing reinforced concrete structures is often more economical and sustainable than rebuilding them. Today the most commonly used techniques based on reparation by externally bonded Carbon Fiber Reinforced Polymers (CFRP). However, bonding concrete beams, particularly damaged beams, suffer from the pre-existing of open cracks at the bottom face of the beams. This paper presents an investigation by finite element method using the general purpose FE software Abaqus to study the flexural behavior of initially damaged concrete beams repaired with FRP plates. In this study, it is aimed to simulate the phenomenon of propagations of cracks where the beam is initially loaded to introduce damage, then, after bonding the FRP plates. The linear elastic fracture mechanics (LEFM) approach is adopted to pursue the stress intensity factor’s evolution in 3-points bending before and after reparation of RC beams. Many parameters were taken account, such us the thickness of the adhesive layer and reinforcing plate, the stiffness, and young’s modulus. Results were identified and discussed.

An analysis of the evaluation of the fracture energy using the DCB-specimen

Biel A., Stigh U.

Archives of Mechanics

2007

Vol. 59, nr 4-5

311-327

The methods to estimate the fracture energy using DCB-specimens as advocated in common standards. For instance, ASTM D 3433 and BS 7991:2001 are based on a compliance method, i.e. on linear elastic fracture mechanics (LEFM). Since the mechanical properties of almost all adhesives are non-linear, errors are generated. In some of the standards, the non-linear behaviour is compensated for by the use of correction terms generated from the experiments. An analysis of the methods of evaluation the fracture energy from experiments is performed. This analysis is performed first by simulating an experiment using realistic data for an engineering adhesive and then, by analysing the results with different methods. In this way, the correct fracture energy is known beforehand and the error in the evaluated fracture energy can be determined. In the present work it is shown that the magnitude of this error depends on the length of the crack. The results show that some commonly used methods generate substantial errors when a large region of non-linear deformation precedes the crack tip. It is also shown that methods based on nonlinear fracture methods do not produce this kind of error.