Experiment and design methodology of a double-layered flange connection in axial loads

This paper introduces a new type stiffened flange connection called inside and outside double-layered (IODL) flange connection for large circular hollow sections (CHS). This kind of connection not only make full use of the inner space of the circular tubes but also avoid safety problems by using smaller bolts and thinner flange plates. The purpose of the research presented in this paper is to thoroughly analyze the behavior of the connections by an experimental testing program and advanced finite element analysis (FEA) and propose corresponding design method for practical engineering. Experiments on four types of down-scaled specimens were performed. Results of advanced quasi-static FEA, using explicit dynamic solver and ductile damage material model for bolts, are compared to experimental results. Failure modes, bolt forces and distribution of stresses in the upper plates, stiffened plates and end plates are analyzed. Design models for high strength bolts, upper plates, stiffened plates and end plates are proposed. The connections designed according to these models will meet the demand of safety and economy.