Inverse analysis for the calibration of FRP - Concrete interface law

Inverse analysis technique is used to derive a non linear mode II interface law for Fiber Reinforced Polymer (FRP) – concrete bonding starting from experimental data. The proposed interface law is based on a fractional formula and includes non linear compliance contributions of adhesive and concrete cover at high shear stresses. It depends on three parameters (maximum shear stress, corresponding slip and an exponent), which are calibrated from experimental results on delamination tests. Values of maximum loads and strains profiles along FRP plates for different bonding lengths are used. Parameter identification is performed by inverse analysis using a Direct Search algorithm. Considerations on well-posedness of the inverse problem adopting different cost functions to minimize the error between experimental and numerical data are given. After parameter identification, numerical results obtained with the proposed interface law are found to be in very good agreement with experimental results.