The influence of member orientation on hollow section joint strength
The influence of the member orientation on the strength of joints formed with square hollow sections is examined. The bird beak joint system is a relatively new truss arrangement for square hollow sections, where the chord and the brace have each been rotated by 45° about their own centreline axes. Based on previous experimental testing it has been suggested that this joint system leads to a stronger joint arrangement. Finite element analysis has been used to study the strength and behaviour of such bird beak joints and to compare them to similar joints in CHS and the traditional RHS configuration to test this claim. A comprehensive study has been undertaken for bird beak X -joints and T -joints and comparisons are made with similar traditional joints in RHS and CHS as the parameters of the width ratio ß, the chord slenderness ratio 2y and the chord length ratio a are varied. Displaced shape and contoured stress plots are included to aid understanding of the failure mechanisms. The finite element work on K -joints allows comparisons of the strength and stiffness of bird beak K -joints with those formed in the traditional RHS configuration as the boundary conditions (at the ends of the members), the brace angle and loading conditions are varied. A limited amount of experimental work has been carried out in the laboratories at Nottingham University, with some assistance from the author, involving the physical testing of bird beak joints so that the finite element models can be validated. This work is reported and examined critically. The conclusions focus on the claims that the bird beak joints are stronger and how they differ from the traditional form of joints. Equations are presented to extend the design information available for a practical parameter range.