ارايه فرمولاسيون محاسبه سختي تيرهاي فولادي ترك خورده بهسازي شده با CFRP

Stiffness Formulation of Cracked Steel Beam Rehabilitated with CFRP

Stiffness degradation and increase in vibration amplitude of cracked steel beams, cause to lose the efficiency of structure in service loads. Bonding CFRP laminates on tension flange is one of the rehabilitating methods of these beams. At present, finite element method is used to calculate the value of stiffness and strength of rehabilitated beams. In this paper, a closed form formulation is presented for calculating stiffness of rehabilitated beams. In this method, the stiffness of rehabilitated beam is calculating based on the stiffness of perfect beam, stiffness of cracked beam, CFRP and adhesive properties and dimensions of structure. Cracked section of beam and reinforcing plate are modeled by an equivalent rotational spring. A procedure is proposed for calculating the stiffness of rotational spring. Formulation is studied in two categories of definite and indefinite beams, and implemented in two special cases of fixed and clamped beams. In order to verify proposed formulation, eighteen hypothetical specimens have been modeled by finite element method. Comparison of proposed formulation and F.E. results shows good agreement. Also another formula is suggested for practical applications by simplification of previous formulas. Simplified and accurate formulas results match very well. Using simplified formula, itʹs not necessary to know the depth of crack to determine the size of reinforcing CFRP plate.