Compression Members with Hollow Sections and Concentric Slotted Gusset Plates – Behavior and Recommended Design Model

In practical applications, compression members in trusses or bracing systems are often composed of hollow sections with slotted gusset plates on both ends. Either a bolted connection with splice plates on both sides or a welded connection are used to achieve a concentric configuration. In recent application cases, members of this type were designed with unusually long gusset plates at their ends, leading to reduced load bearing capacities.
In the present paper, the load carrying behavior of such members is shown by means of realistic numerical calculations. The resulting compression member capacities are compared with the design models for flexural buckling as they are commonly employed in practice.
It will be shown that these models significantly overestimate the compression member capacity – particularly in cases with low slenderness. Interestingly, imperfection forms similar to the second eigenmode often lead to the most critical design situation. The influence of residual stresses due to the welding of the gusset plate to the slotted hollow section is also studied in detail.
On the basis of these numerical results, an improved engineering design recommendation for the practical verification of the gusset plate stability could be developed, which should be used in addition to the conventional member buckling verification.

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