Selection of Appropriate Material, Construction Technique, and Structural System of Bridges by Use of Multicriteria Decision-Making Method

Decision makers in the transportation industry search for a systematic approach to select an appropriate structural system, construction method, and material for bridges. Simple mathematical methodologies are needed to consider different stakeholders’ perspectives. With criteria that occur simultaneously in selecting appropriate material, construction technique, and structural system of bridges, invalid and unexpected results may occur from such complexity. The decision-making process is usually done subjectively by designers and requires much data and extensive experience in bridge design. To address these challenges and assume all substantial criteria within the framework, the PROMETHEE (Preference Ranking Organization Method for Enrichment Evaluation) multi-criteria decision-making method is used. It is not sensitive to the number and definition of the criteria. The PROMETHEE method is based on the pairwise comparison between alternatives for constructing an outranking relationship to show the degree of dominance of one alternative over another. A case study of the Kashkhan Bridge in Iran is presented to demonstrate implementation of the PROMETHEE method and show how such a decision-making methodology can assist experts in making informed decisions based on a set of comprehensive criteria in the conceptual design stage. Some novel and effective criteria in this study are combined and synthesized to select the appropriate superstructure. Criteria weights and preference and indifference thresholds are collected through questionnaires filled out by bridge experts. Results of the case study show that the most appropriate system for the Kashkhan Bridge is the box girder system with the balanced cantilever method and posttensioned concrete material.