CEMP-E
TI 809-07
30 November 1998
rather than many with low lateral load capacity. Therefore all shear panel design guidance presented
here shall require the use of anchors. Anchor design is presented later in this document (Paragraph 10).
b. Screwed Fastener Connection Design. Self-tapping screwed connection capacity definition
shall follow AISI guidance (Section E4 Screw Connections). Screws shall be installed and tightened in
accordance with the manufacturer's recommendations. Screw connections loaded in shear can fail in
one mode or in combination of several modes. These modes are screw shear, edge tearing, tilting and
subsequent pullout of the screw, and bearing of the joined materials. The commentary of the AISI
Specification (E4.3) gives further explanation and illustration of these modes of failure. The AISI
provisions focus on the tilting and bearing modes of failure. Two cases are given depending on the ratio
of the connected member thicknesses. Normally the head of the screw will be in contact with the thinner
material, t1. However, when both materials are the same thickness or the thicker member is in contact
with the screw head, tilting becomes a more critical mode of failure. The AISI Section E4 guidance on
design shear strength per screw, Ps applied to diagonal strap-to-column screw connections is
summarized in Appendix C (Paragraph C15). The modes of failure expressed in Equations C-48 through
C-52 are defined alongside the equations.
Minimum spacing guidance (AISI E.4.1) requires that the distance between centers of fasteners shall not
be less than 3d, where d is the nominal screw diameter.
Minimum edge and end distance guidance (AISI E.4.2) requires that the distance from the center of a
fastener to the edge of any connected part shall not be less than 3d. If the connection is subjected to
shear force in one direction only, the minimum edge distance shall be 1.5d in the direction perpendicular
to the force.
Finally, the minimum number of screws required at each diagonal strap-to-column connection, nscrews is
calculated as follows:
Psu
≥
n screws
(Eq 3-16)
n sPs
The nominal shear strength of the screws shall be determined based on manufacturer's data (AISI
E4.3.2), which must be based on tests according to AISI Section F1(a). This nominal shear strength of
approved screws must not be less than 1.25Pns where Pns is defined by Equations C-48 through C-52.
c. Design Rupture Strength. The design shear strength along a potential shear rupture plane
between fasteners of connected members, V shall be determined as below (AISI E5 Shear Rupture,
Specification and Commentary, AISC J4 Design Rupture Strength). The AISI commentary states that
their shear rupture provisions are based on AISC provisions. The AISI provisions conservatively neglect
the greater strength that AISC allows for the tensile rupture plane. The guidance below adds the greater
strength allowed by AISC for this tensile rupture plane.
V = 0.6φ v Fu A nv
(Eq 3-17)
Where:
Fu = the ultimate strength of the member being evaluated.
Anv = the net area subjected to shear along the rupture plane being considered.
The design tensile strength along a potential tensile rupture plane between fasteners of connected
members, T shall be determined as follows:
T = φ t Fu A nt
(Eq 3-18)
3-10
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