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ABSTRACT:The doubler-plate is widely used to improve the behavior of truss joints, and it has been proven to be effective in increasing the load carrying capacity of circle or square hollow section joints, yet the current design approach for doubler-plate reinforced joints is elementary. This study investigates the behavior of doubler-plate reinforced square hollow section (DPR-SHS) T-joints under brace compression, by experimental tests and finite element analysis (FEA). Details of the test arrangement were summarized, and the behaviors of failure modes, strain distribution and deformation characteristics of the specimens were analyzed. After confirming the accuracy of the finite element model with the test evidence, the reinforcement mechanism of doubler-plate was analyzed by parametric study. Both the experimental and FEA results shown the compression strength of the joint is significantly improved by welding a doubler-plate on the surface of the chord. The reinforcement efficiency of the doubler-plate increased with the increase of doubler-plate width and length, yet decreased with the increase of doubler-plate thickness and yielding strength. The thickness of doubler-plate influences the strength of the joint more than the width or length. Given a proper thickness, the reinforcement mechanism of the doubler-plate was yielding together with the chord flange. Finally, design formulas for DPR-SHS T-joints were proposed using yielding line method, which agree well with the experimental and FEA results. Yet the formula of Eurocode3-1-8 seems to oversimplify the design of DPR-SHS joint, which may lead to inaccurate estimation of the compression strength of the joint.

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