Exploratory Study of the Fin Plate Connections of a Circular Hollow Section Structure

Four specimens of a circular tubular structure with fin plate connections were load tested to failure and compared with the corresponding finite-element method (FEM) analyses. There have been no investigations of such a circular tubular structure, which is a basic module of a space frame, reported in the literature. The modes of failures, initial stiffness, first yield loads, and ultimate load capacities were studied. Comparison of results of the load tests and finite-element analyses based on first yield load of the circular tubular structure was made. A parametric study of the fin plate connections in a circular tubular structure investigated in the present study was carried out using finite-element analyses. The exploratory study seemed to suggest that the thickness and depth of the fin plate as well as the diameter and thickness of the vertical circular hollow section (CHS) were important parameters in affecting the behavior of CHS structures studied, but the length of the fin plate was not. The major principal stresses of the vertical CHS exceeded that of the fin plates. Four failure modes were observed in the load tests of the four specimens. The FEM analyses showed that attainment of the required load-carrying capacity of fin plate connections in a circular tubular structure was highly dependent on the thickness of the fin plate and the level of accuracy (workmanship) achieved in the fabrication process. The present exploratory study highlighted the importance of the need to implement a quality assurance and quality control measure to gauge the magnitude of eccentricity of the fin plate connection introduced during the fabrication process for each and every fin plate connection to ensure that the magnitude of eccentricity was within the tolerance spelled out in the contract documents. This also means that in the design of fin plate connections in circular tubular structures, the choice of the thickness of the fin plate must take into account the risk of this unavoidable geometric imperfection introduced during the fabrication process. The findings of the exploratory study provide a useful guide for the full investigation of the behavior of such fin plate connections of circular tubular structures.