Floor-To-Wall Connection Behavior in Ledger-Framed Cold-Formed Steel Construction

Abstract eng:
The objective of this paper is to investigate the moment-rotation behavior of floor-to-wall connections used in ledgerframed cold-formed steel construction with full-scale experiments. Recently completed research employing full-scale shake table tests on a two-story ledger-framed cold-formed steel framed building exhibited beneficial lateral system response that far exceeded predictions. One hypothesis is that the stiffness of the floor-to-wall connections, and the repetitive nature of this connection, provided beneficial semi-rigid frame response that augmented the designed shear walls. Monotonic and cyclic full-scale connections were tested and reported here to examine the strength and stiffness, so that this hypothesis may be explored further. The test matrix is designed to evaluate the presence of floor sheathing, applied moment/shear ratio of the joist, joist-to-ledger clip angle location (inside or outside of the joist section), presence of top and bottom screws connecting the joist and ledger flanges, and location of the joist relative to the studs. The results indicate that the connection details and loading conditions drive not only the capacity but also the observed limit states. Current design for this connection assumes pure shear and is controlled by screw shear capacity. However, screw pull-out, ledger flange buckling, and stud web crippling are all observed in the testing. These findings will be used to support future 3D seismic building analysis and design and to develop improved design guidance for ledger framing.

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