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Abstract

Little guidance is available in the literature that is suitable for use in the design of extended single-plate connections. In particular, these connections have not been studied sufficiently for scenarios that involve axial load, which is relatively common in industrial applications. To address this shortcoming, an investigation into the behaviour of extended single-plate connections was completed by testing 23 full-scale specimens. Connections with and without stabilizer plates were tested that varied in plate thickness, plate depth, and the number of horizontal bolt lines. Horizontal loads varied from 500 kN in compression to 200 kN in tension. The influences of the test variables on connection behaviour, capacity, and failure mode are discussed. Among the findings of this research are that despite their slenderness these connections tend to be quite ductile, and the capacities of the unstabilized connections without axial load were much larger than those predicted by available design provisions.

5. Summary and conclusions

The capacity of an extended single-plate connection can, in general, be increased significantly by using stabilizer plates. If stabilizer plates are not used, the capacity can instead be increased by using a deeper plate with more bolts. However, increasing the plate thickness does not necessarily strengthen the connection, as it may reduce ductility and thereby trigger another failure mode; this concept is reflected in the design procedures provided in the Steel Construction Manual [1]. When stabilizer plates are used, additional shear capacity can be realized by increasing the plate depth and number of bolts, or the plate thickness (contrary to the observations for the unstabilized specimens). As out-of-plane deformation of the connection plate governed the ultimate strength of the stabilized extended single-plate connections, the reduction in shear strength with the addition of compressive load was observed to be more rapid than for the configuration without stabilizer plates, whose capacity may not decrease at all under small horizontal compressive loads. Eight potential failure modes were studied in this research and should be considered during design: weld rupture, bolt fracture, column web yielding, plate rupture, gross section yielding, net section fracture, bolt bearing, and out-of-plane deformation. Weld rupture and bolt fracture were the dominant observed critical failure modes for extended single-plate connections without stabilizer plates, and for those with stabilizers it was out-of-plane deformation. For both stabilized and unstabilized single-plate connections, it is desirable to proportion the connection to ensure yielding of the plate cross-section prior to the ultimate load capacity being reached, as plate yielding plays a significant role in achieving ductile connection behaviour. This yielding occurs as a result of the combination of flexural and shear actions. While bolt bearing played a role in several of the tests, in no case was bolt tearout observed. In addition to the failure modes observed in the tests, other potential modes such as block shear should be considered during design. Moreover, if adequate lateral beam bracing is not provided near the connection, modes such as plate twisting and lateral-torsional buckling of the overall member may govern.