Calibration of a mode II FRP-Concrete interface law by inverse analysis

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 for different bonding lengths and strains profiles along FRP plates are used. Parameter identification is performed by inverse analysis using a Direct Search technique. Considerations on well-posedness of inverse problem adopting different cost functions are given. After parameter identification, numerical results obtained with the proposed interface law are found to be in very good agreement with experimental results.