Using Response Surface Methodology and providing a modified model using whale algorithm for estimating the compressive strength of columns confined with FRP sheets

This study presented a modified model for determining the compressive strength of square and rectangular concrete columns using whale algorithm and a widespread database. In this model, the effective strain coefficient of FRP and cross section coefficient considered as an individual coefficient. Furthermore, the coefficients of the rising strength for specimens with unconfined compressive strength in upper and lower of 35 MPa are differently considered. In addition, Response Surface Methodology used for estimating the compressive strength of the confined specimens by FRP. Finally, results compared with the existing models. The predictions of the modified model and RSM show satisfactory estimations. So that RSM and the modified model have increased R2 approximately 34% and 26% rather other models, respectively.