Strength of longitudinal X-type plate-to-circular hollow section (CHS) connections reinforced by external ring stiffeners

This paper presents an experimental test and finite element (FE) study on the ultimate strength of longitudinal X-type plate-to-circular hollow section (CHS) connections reinforced by external ring stiffeners (abbreviated as PCE connections) under in-plane bending moment. Static tests on four large-scale specimens were performed under both symmetrical and anti-symmetrical loadings. Local axial buckling and transverse plastic deformation failures on PCE connections were observed from the test. Further FE analysis reveals that the external ring stiffener can achieve effective strengthening of the connection and the failure modes are affected by the size of the ring. A total of 541 PCE connections with a various range of geometric configurations and chord stress levels were analyzed and the results obtained were transformed into the ultimate strength of "ring models". Based on the regression analysis of numerical simulation database, the current design equations by JSTA were re-assessed and a set of novel design model has been proposed utilizing the mathematic design model for transverse X-type plate-to-CHS connections by CIDECT design guide. The proposed design model tends to have practical significance by offering a design guideline for the similar connections.