A new decision model for weighting of experts and selecting the best sustainable supplier in project procurement problems under a grey environment

Project procurement is one of the essential parts of the project covering a large portion of project costs. Supplier selection is one of the significant issues in project procurement. The appropriate supplier must be selected before ordering the materials needed for the project. Hence, a new combination of COPRAS and GRA methods is presented for choosing the best project’s supplier under uncertain conditions in this paper. Moreover, the weight of criteria is specified utilizing the multi-objective optimization model (MOOM). Furthermore, in group decision-making, decision-makers' importance is different because of varying education, views, and experience. Hence, determining the weights of decision-makers is inevitable. Nevertheless, decision-makers' importance is specified by a new version of a combination of COPRAS and GRA methods. To evaluate the proposed model's performance, a numerical example is solved, and the results are investigated.