Numerical modelling of preloaded RC beams strengthened with prestressed CFRP laminates

The paper presents the research on reinforced concrete beams strengthened with pre-tensioned CFRP laminates under self-weigh only and self-weight and external preload. In the first part the results of experimental campaign (Kotynia et al., 2013) are briefly described and discussed. Next a two-dimensional plane stress model of beams was developed on the basis of experimental observation. The model takes into account the nonlinear behaviour of concrete, steel bars and the concrete-to-laminate interface. A new uncoupled interface model was developed and programmed in order to properly describe the concrete-to-laminate connection for severely cracked structures. Numerical simulations performed for the calibrated material parameters exhibit very good convergence with the experimental results. The analysis confirmed suitability of the model to predict behaviour of RC members strengthened in flexure with CFRP materials in the whole range of loading. Moreover, in this part of the paper the numerically obtained effectiveness of active strengthening in relation to general passive methods of strengthening RC members in flexure was analysed. The calculations show that prestressing increases load bearing capacity in comparison with passively strengthened elements. The second part of the paper contains parametric study of the effect of concrete class, steel ratio, CFRP laminate width and stiffness, maximum concrete-to-laminate bond strength, loading configuration and preloading on load-deflection behaviour and load capacity of actively strengthened beams. The performed parametric study considerably broadened the scope of the experimentally investigated cases by Kotynia et al. (2013).