Effectiveness Factor of Concrete Based on Lower - Bound Analysis of Deep Beams Strengthened with CFRP

Abstract

The effectiveness factor of concrete is existing to overcome the shortcomings of applying the plasticity theorem to analyse the behaviour of reinforced concrete and account for the limited ductility of concrete. The value of the effectiveness factor mainly depends on the material properties, the geometrical dimensions and the reinforcement details. There is disagreement among different codes of practice on the value of the effectiveness factor. The main aim of this research is to propose a new equation for the effectiveness factor of concrete that can be implemented in the lower-bound analysis of simply supported deep beams strengthen with CFRP. Moreover, the study assesses the use of different effectiveness factor expressions in the lower bond analysis of deep beams strengthened with CFRP. A model of a strut and tie is proposed to predict the final load for simply supported deep beams that fail to shear, taking into account the effect of the total depth of the deep beams and the angle of inclination of the strut according to the design codes. The accuracy of the proposed model is verified based on a database of 126 samples collected from previous studies. The analysis showed that the shear strength of deep beams strengthened with CFRP depends on more than one variable. Among the different effectiveness factor equations considered in this investigation, for the range of beams considered, the most accurate prediction was achieved using the proposed effectiveness factor equation with a mean of 1.00, a standard deviation of 17% and a coefficient of variation of 2.0%.