Determining most significant project risk's categories with considering causal relations between them in the fuzzy environment

Every project has many risks and as there are many complexities in projects today، recognizing the most important risks is essential for projects'' success and efficiency. In this research، we tried to determine most significant risk''s categories in the framework of risk breakdown structure of 4th edition of Project Management Body of Knowledge Guide that can be generalize to all projects in Iran. With considering dependencies and interactive relations between risks of project، we used DEMATEL method to determine the most significant project risk''s categories on the basis of risk breakdown structure of 4th edition of Project Management Body of Knowledge Guide. Also fuzzy set theory was applied to measure experts'' subjective judgments، experts who have rich expertise and knowledge in Iranian projects were selected to evaluate the influences. The results revealed that «External»، «Technical»، «Project Management» and «Organizational» risks are significant and in the most important risk''s category which is «External»، «Regulatory» risks and in «Technical»، «Project Management» and «Organizational» risks، «Technology»، «Estimating» and «Project Dependencies» are the most important risks respectively and should be paid more attention because they were in the first rank of importance.