Prédiction de la dispersion du chargement d’assemblages boulonnés à bride pleine lors de serrage multi-passes

Abstract

In the industrial domain, bolted joints play a fundamental role in ensuring the secure connection between equipment, pipelines, or pressurized piping systems. Within this framework of safety and reliability, the achievement of a uniform and effective tightening of bolts is of paramount importance. Progressive tightening sequences, often carried out in several passes and following well-established tightening patterns, already represent a recognized safety measure. Nevertheless, these procedures are inherently time-consuming and, in certain cases, lack precision. The present study addresses this limitation by developing an analytical and numerical framework capable of predicting the change of preload that occurs during multi-pass tightening of bolted flange joints with blind covers. Such losses originate from elastic interactions between bolts, a phenomenon that must be understood and anticipated to optimize the tightening process. The developed analytical model is based on the classical theory of circular plate under a concentrated force, which has been adapted here to the specific investigation of elastic interactions in bolted flange assemblies. In addition, this formulation is coupled with the approach proposed by Zhu (Zhu, Bouzid & Hong, 2018a), allowing for the identification of local compliance values at each bolt position to predict the bolt load scatter. The analytical predictions are subsequently validated through finite element simulations performed on blind flanges of different dimensions and classes, namely an NPS 4 Class 900 flange, an NPS 24 Class 150 and a larger NPS 52 Class 600 flange. Furthermore, an experimental campaign conducted on NPS 4 Class 900 flanges serves to corroborate the robustness of the proposed methodology. The outcomes of this research provide a clearer understanding of load scatter in bolted flange assemblies during tightening and contribute to the mitigation of unnecessary or costly handling operations, thereby enhancing both efficiency and structural safety.

Date	14 Jul 2026
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Hakim A. Bouzid (Supervisor)