Ultimate strength of welded joints in tubular steel structures

An experimental and theoretical investigation of the strength of welded T-joints has been carried out, and the following tests were conducted:- 17 No. tests for ultimate axial strength (Pu) 17 No. tests for ultimate bending strength (Mu) 71 No. tests for combined axial and bending strength The parameter ranges of the tests were:- brace diameter/chord diameter: 0.42, 0.53, 0.67, 0.77, 1.0 chord diameter/chord thickness: 18, 21, 23, 32 brace thickness/chord thickness: 0.63 - 1.4 All test specimens were steel to BS Grade 43C, with an average nominal yield strength of 350N/mm[sup]2. The interaction between axial and bending strength has been studied experimentally and theoretically and a relationship has been established. Formulae are proposed for calculating the ultimate axial strengths of welded T-joints and the ultimate bending strengths of welded T-joints. Numerical analysis of the experimental test results has been carried out using regression methods. A computer program has been developed to facilitate this task. Design equations have been deduced as a result of the regression analysis. A theoretical study of T-joint stress distribution under axial and bending loads has been carried out using an elastic finite element system called LUSAS, which has been developed at Imperial College, London by Dr. P. Lyons. Results have been plotted using programs developed at Kingston Polytechnic. A review of the twenty existing methods for calculating the ultimate static strengths of welded T, Y. X, K and N-joints in circular hollow steel sections has also been carried out. Calculated loads have been compared with 450 existing test loads, and the results have been analysed statistically. Each formula has been reviewed and discussed and, as a result of the statistical analysis, recommendations for design formulae for K, N and X-joints have been made