Mechanical analysis of reinforced concrete box beam strengthened with carbon fiber sheets under combined actions

A mathematical model is developed to investigate the torsional behaviour of reinforced concrete box beams strengthened with carbon fiber sheets under combined actions of torque, bending and shear. The new method is based on the diagonal compression field theory. Thirty-seven equations are derived from equilibrium, compatibility, deformation corresponding, and materials conditions to solve the problem. It avoids the need for iterations by making simplifying assumptions about the perfect bond between carbon fiber sheets and concrete and the uniform distribution of stress in diagonal concrete struts. Static analysis of the four reinforced concrete box beams strengthened with carbon composites under combined actions has been performed. Very good agreement is observed with available experimental data.