Static strength of high strength steel CHS X-joints under axial compression

This paper presents an investigation on the static strength of high strength steel circular hollow section (CHS) X-joints subjected to axial compression in the braces which failed by chord face plastification. Using validated finite element models, extensive numerical simulations were conducted considering a wide range of geometric parameters and chord preload ratios. The material properties of high strength steel with nominal yield stresses of 700, 900 and 1100 MPa were carefully incorporated in finite element models. The static strengths obtained from numerical analysis in this study and experimental tests in the literature were compared with those calculated from mean strength equations on which the design equations in Eurocode EN 1993-1-8 and the CIDECT design guide are based. The comparison results show that the mean strength equation adopted by the CIDECT design guide is generally more accurate than that of EN 1993-1-8. The mean strength prediction of the CIDECT design guide without using reduction factors of joint strength is relatively accurate for CHS X-joints with nominal steel yield stresses ranging from 650 to 700 MPa. However, the mean strength predictions of EN 1993-1-8 and the CIDECT design guide generally become more unconservative with increasing steel yield stress. The mean strength equations are unconservative for CHS X-joints with nominal steel yield stresses exceeding 700 MPa.