What Is the Rope Effect and Is It Considered in Connection Design Approaches in North America?

The rope effect (or “string effect”) describes an additional strengthening component caused by the axial capacity of laterally loaded dowel-type fasteners.
For yield modes involving fastener rotation or fastener yielding, the axial capacity of the fastener becomes engaged, generating a normal force that pulls the connected members together which produces friction in the shear plane. With significant deformations, the tension component of the fastener contributes additional connection strength. Slender fasteners with high axial and plastic capacities have inherent potential to contribute additional connection strength to shear connections through the rope effect.

Design standards in Europe contain provisions for the additional strength contribution of the rope effect through a correction term to the yield model equations [EC5 Cl. 8.2.2 (2)]. CSA O86 incorporates the rope effect in Cl. 12.11 for wood screws through embedment strength f3 where the failure mode is fastener yielding. At present, the lateral connection design procedure for self-tapping screws follows conventional Yield Limit Equations in NDS 2018, and Cl. 12.6.6 for lag screws in CSA O86, both of which do not include provisions for the rope effect.
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Relevant Technical Resources

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