What Spacing Requirements Should I Follow When Designing Lateral Connections with Fully-threaded Inclined ASSY Screws?

The inclination of the screw axis with respect to the grain orientation, it can make it confusing to determine the spacing requirements of a connection.

Lateral connections using axially loaded inclined ASSY self-tapping screws have different detailing requirements than fasteners loaded for either purely axial or purely shear connections. The axially loaded inclined Assy screws are loaded primarily in tension or compression following the Truss Model, therefore the detailer should give special attention to end distances, edge spacings, and center to center spacings.

The main difference with a purely axial connection is that distance, SP axial, needs to be measured as shown in the figure below. It is important to note that the spacing is measured perpendicular to the screw axis, leaving larger spacing distance on the surface of the element. For each member of the connection, the following procedure may be used:

  1. Locate the center of gravity (denoted Cs for side member and Cm for the main member) of the screw portion in each member. This is most commonly calculated as half of the penetrating screw length.
  2. The designer must ensure that all spacing requirements are satisfied with respect to the C∆ = 1.0 for both main and side members. Detailed step-by-step procedures can be found in the ICC-ES 3178 Evaluation Report for ASSY Fully-Threaded Self-Tapping Screws.

Inclined self-tapping screws can also be installed in conjunction with partially-threaded shear screws as explored in the article “Can We Add up Force Contributions from Inclined Screws and 90° Shear Screws?”.  For the center to center spacing requirements between inclined and shear screws, the most conservative spacing should be considered.

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