Proposed In-Plane Buckling Brace Connection Detailing to Prevent Fracture at High Lateral Drifts

The premature failure of gusset plate interface welds under higher drift conditions significantly hampers the performance of braced frame systems. Traditional methods for designing connections in Concentrically Braced Frames (CBFs) predominantly focus on brace action forces, often overlooking the substantial impact of frame action forces. The intricate stress distribution within the gusset plate further complicates accurate assessments of these forces. Neglecting or inadequately considering frame and brace actions can result in unreliable force estimations on gusset plates, potentially leading to interface connection failures. This study aims to unearth the reasons behind the failure of interface welds in the in-plane buckling (IPB) braced system and offer practical design recommendations to forestall premature failure. The effectiveness of existing analytical methods in estimating interface forces attributable to brace and frame actions under higher drift conditions is evaluated. Notably, the stress and strain at the gusset plate’s tip on the beam side considerably exceed those at other parts of the interface. The current design methodology proposed by AISC for determining weld sizes appears ineffective in averting premature failures. This inadequacy primarily stems from the accumulation of plastic strain at the gusset plate’s tip during higher drift conditions. Finally, the present study proposed an in-plane buckling brace connection detailing to prevent fracture under high lateral drifts, offering a promising path toward enhanced braced frame seismic performance.