Influence of frost-damage on reinforced concrete beams Material properties and FE analyses of mechanical behaviour
Tutor / director / evaluadorLundgren, Karin
Tipo de documentoProyecto/Trabajo final de carrera
Condiciones de accesoAcceso restringido por acuerdo de confidencialidad
In the last years, knowledge about how frost-damage affects the behaviour of concrete structures has been developed and presently some related studies can be found. It has been generally proved in all tests and analyses carried out since now, that when concrete is severely damaged by freezing, a reduction of the load-carrying capacity and stiffness of the structure and a possible change of the failure mode are detected. Due to the change in the micro and macro structure of concrete, the material properties of frost-damaged concrete may not be the same as for undamaged concrete. The aim of this master thesis is to study the influence of frost-damage on reinforced concrete beams and to analyse the mechanical behaviour of the beams. Material and bond properties of frost-damaged specimens have been tested by Zandi Hanjari (2008). The results from these experiments were used to choose the input data for non-linear analysis of twelve beams, with different geometries and reinforcement content. Six beams were analysed with undamaged concrete properties and the other six with damaged concrete properties, in order to study the effect of frost-damage on the beams. The stress-strain and bond-slip curves, the Young’s modulus of elasticity and the fracture energy were introduced in the analyses for both undamaged and damaged concrete. Results from experiments on the same frost-damaged reinforced concrete beams, performed by Hassanzadeh and Fagerlund (2006), were compared with the numerical results. Moreover, the results obtained in this thesis were compared with previous analyses, carried out by Zandi Hanjari et al. (2008). The numerical results of this thesis underestimate the stiffness and the strength of large beams with crushing failure. This may be due to the fact that all the finite elements were considered to be as damaged as the outer part of concrete. While in reality, the level of damage is not constantly distributed along the cross section; that is the closer it is to the surface of concrete, the more damaged it would be. On the other hand, for small beams with crushing failure, which are believed to be more damaged than the larger ones, the same assumption led to an overestimation of the loadcarrying capacity. In general, the numerical results carried out with new input data showed a general improvement when predicting the deformations and load capacities of the beams. The failure modes were also well predicted and the shape of the force-deformation curves appeared to be fairly better fitted with new input data analyses. To sum-up, the experimental research on material properties for frost-damaged concrete seems to have been really helpful to better predict the mechanical behaviour of the tested damaged beams.
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