Optimized design of fillet welds for CHS joints according to EN 1993-1-8

Designing fillet welds using the directional method of EN 1993-1-8 requires the consideration of force components, converted to stresses, located in the plane of the weld throat. For circular hollow section (CHS) joints, considering these “stress components” can be exceedingly difficult. An approach to applying the directional method to CHS joints is developed in this paper. The directional and simplified methods of EN 1993-1-8 are then evaluated against available finite-element data, validated from recent tests on weld-critical CHS X-joints according to the standard evaluation procedure of EN 1990. Despite inherent non-uniform loading of the weld around the perimeter of the brace, it is shown that taking the total weld length to be effective is safe for both methods. Procedures are given so that these methods can be used to design fillet welds in CHS joints as “fit-for-purpose”, as permitted by EN 1993-1-8 and ISO 14346, and new design charts are produced for minimum fillet welds that develop the axial capacity of the connected brace.