SIMPLIFIED LOAD-DEFLECTION CALCULATIONS OF FRP STRENGTHENED RC BEAMS BASED ON A RIGOROUS APPROACH

Abstract eng:
The external FRP flexural and shear strengthening of RC beams is a well-established practice for structural rehabilitation and upgrade. For establishing a deflection calculation procedure, some investigators have proposed empirical modifications to the current ACI equation. Others used numerical analysis to generate such deflection computations. Alternatively, the present work develops an analytical solution for the same calculation at any load stage. The solution assumes a trilinear moment-curvature response. This model incorporates some tension stiffening effects and assumes the section to be fully cracked only upon or near steel yielding. A closed form equation is presented for the case of four-point bending as well as uniform loading. Comparisons with experiments indicate the effectiveness of the procedure for properly anchored plates. An extensive parametric study is conducted to reveal a single linear relationship between the cracked moment of inertia of the section (Icr) and the overall effective beam moment of inertia at yielding (Iey) for a wide range of geometric and material parameters. A similar relationship holds between the moment of inertia of the section at the ultimate moment (In) and the corresponding effective value for the entire beam (Ien). This greatly simplifies the deflection calculation as illustrated by comparisons with the rigorous analytical approach and the experimental results.

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