Cold-formed steel ledger-framed construction floor-to-wall connection behavior and strength. (May 2019)

• Record Type: Journal Article
• Authors: Ayhan, D.; Schafer, B.W.
• Is Part Of: Journal of constructional steel research. Volume 156(2019)
• Page Start: 215
• Page End: 226
• Publication Date: 2019-05
• Subjects: Cold-formed steel -- Ledger framing -- Floor-to-wall connections -- Moment-rotation -- Stud web crippling; Steel, Structural -- Periodicals; Building, Iron and steel -- Periodicals; Acier de construction -- Périodiques; Construction métallique -- Périodiques; 624.1821
• DOI: 10.1016/j.jcsr.2019.01.021
• Languages: English
• ISSNs: 0143-974X

Abstract

Abstract: The objective of this paper is to investigate the moment-rotation behavior of floor-to-wall connections used in ledger-framed cold-formed steel building 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 utilizing oriented strand board (OSB) sheathed shear walls and floors exhibited beneficial lateral system response that 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 connection strength and stiffness, so that this hypothesis may be explored further in the future. The test matrix is designed to evaluate the presence of OSB 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 how the connection details and loading conditions drive the moment-rotation response; in addition, several limit states not checked in current design were also observed. Current design for this connection assumes a pure shear condition governed by screw shear capacity. However, ledger-to-stud screw pull-out, ledger flange buckling, and stud web crippling limit states are all observed in the testing. Design methods to support strength predictions consistent with the observed limit states are developed and assessed. The testing provides needed characterization of cold-formed steel floor-to-wall performance and is augmented by improved design methods for this detail. Highlights: Stiffness and failure modes in floor-to-wall connections for CFS framing provided. Floor-to-wall connections in CFS framing may be subject to unexpected limit states. Joists in CFS framing can potentially cripple studs at large rotation. Ledger flange buckling is a favorable limit state in CFS floor-to-wall connections. Design methods are provided to predict floor-to-wall CFS connection behavior.