Static behavior of compressed braces in RHS K-joints of hot-dip galvanized trusses

• Design of joints in galvanized tubular steel structures is not covered by codes.
• An experimental and numerical research program on K and N-joints has been carried out.
• FE models including nonlinear buckling were validated with full scale tests of joints.
• The validated finite element models were extended to a full range of joints.
• Main conclusion is that vent holes have no influence on the joint resistance.

This paper presents the results of an investigation to evaluate the influence of holes on the mechanical resistance of K-joints in hot-dip galvanized tubular structures. Such holes are used as vent in Warren and Pratt lattice girders using rectangular hollow sections and K- and N-joints. Full scale joints were tested in which a compression load was applied on one brace member with one of the ends of the chord being left free. The other two ends of the joint were pinned to ensure predominantly axial force transfer. The test program examined the effects of a number of variables, including the presence or absence of the vent hole, the dimensions of the RHS, the ratio of the brace/chord wall thicknesses and the angle between the brace and the chord members. These tests were also numerically simulated for validation of the simulation model. It is expected that this research will form the basis of recommendations to help structural engineers in designing galvanized hollow truss structures with vent holes.