Design of fillet welds in RHS-to-RHS moment T-connections under branch in-plane bending

Abstract

Non-linear finite element (FE) models were developed to assess the AISC 360-16 Chapter K design approach for fillet welds in rectangular hollow section (RHS) moment T-connections under branch in-plane bending. The FE models were validated by comparison of the weld fracture moments, load-deflection responses, and spot-strain measurements to results from six previous, large-scale, weld-critical experiments. Based on all available experimental and FE data, the AISC 360-16 design approach is shown to be over-conservative. A key reason for this is that it does not account for bearing between the branch and chord on the compression side of the connection. New design formulae that take bearing into account are hence proposed. These formulae are shown to provide more accurate predictions of fillet weld strength in RHS moment T-connections under branch in-plane bending, and yet still achieve a safety (reliability) index that meets the AISC's target value of 4.0 for connections. The scope of this paper covers connections with all-around fillet welds and branch-to-chord width ratios up to 0.85.