Forming risk clusters in projects to improve coordination between risk owners

9 Due to the growing complexity of projects, their risks have increased in number and criticality. Risk lists thus 10 need to be broken down into smaller, more manageable clusters. Classical clustering techniques are generally 11 based on a single parameter, like risk nature, criticality or ownership. Risk interactions are therefore not prop12 erly considered when building up clusters. That is why this paper aims at grouping risks so that the communi13 cation and coordination between the actors who are committed in the management of the project and its risks 14 are facilitated. Thework is based on an optimization algorithm which maximizes interaction rate within the 15 risk clusters. This paper focuses on two additional points. First, the optimization problem formulation is 16 enriched by some constraintsrelated to the risk owners, not only to the risks. Second, a frequency approach is 17 introduced, to test different configurations, in order to improvethe robustness of the clustering decision. It 18 enables meaningful and operationally realistic actors groups to be organized, regarding not only the interac19 tion rate between risks but also the relationships between risk owners. Our clustering approach encourages 20 people to meet together and communicate/ coordinate better, which we hope will contribute to prevent some 21 undesired complex phenomena. 22