an extended grey relational analysis based on copras method for sustainable supplier selection in project procurement problems

The sustainable supplier selection (sss) problem is an integral part of project procurement management. in this paper, a new extended grey relational analysis (gra) based on the complex proportional assessment (copras) is applied for sss problems for using the merits of these two methods simultaneously. furthermore, a new multi-objective optimization model (moom) is developed to obtain the objective weights of criteria. moreover, to illustrate the uncertainty of real sss problems and derived uncertainty of experts’ judgments, grey numbers are employed. to reduce the reliance on the experts, a new moom is developed for criteria’ weights determination. finally, the performance of the introduced method is demonstrated by solving a numerical example.