Moment-rotation response of cold-formed steel joist-to-ledger connections with variable-finishes in ledger-framed construction

• Published in: Journal of constructional steel research 2021-01, Vol.176, p.106396, Article 106396
• Main Authors: Castaneda, Hernan, Peterman, Kara D.
• Format: Article
• Language: English
• Subjects: Cold-formed steel; Computational modeling; Diaphragm; Fastened connection; Moment rotation
• ISSN: 0143-974X; 1873-5983
• DOI: 10.1016/j.jcsr.2020.106396

Ledger framing is the dominant framing system in North American cold-formed steel (CFS) construction. In this system, the floor, which is typically sheathed with oriented strand board, is framed into the top of the wall via a rim track (ledger) and clip angle connection. The diaphragm is essentially hung from the walls. Recently completed experimental work involving full-scale shake table tests on a ledger-framed CFS building exhibited the presence of alternate load paths that contributed to the lateral force resisting system. Within the goal of quantifying this contribution to the overall diaphragm response, experimental tests on joist-to-ledger connection have demonstrated to have a complex behavior involving limit states such as ledger flange buckling, stud web crippling, and fastener pull-out. Current design practices do not account for these limit states. To improve design recommendations and understanding of load transfer mechanisms, a robust finite element model for a joist-to-ledger connection in ABAQUS, validated via existing experimental tests, is presented herein. Experimental testing on the pull-out capacity of screw-fastened connections was conducted for implementation into the finite element environment. Results were then implemented directly in ABAQUS as connection behavior. Generally, the modeling approach accurately captures connection capacity and behavior. In addition, influence of other floor sheathing materials, fiber cement board and steel deck, on the moment-rotation stiffness and strength of this connection is explored. In steel deck sheathing, effects of deck thickness and fastener spacing are explored. This work enables predictions for both design and system-scale characterization. [Display omitted] •Moment-rotation response of CFS joist-to-ledger connections with variable finishes.•Experimental characterization of fastener pull-out in CFS-to-steel connections.•Finite element model (FEM) for joist-to-ledger connections in CFS floor diaphragms.