Product Technical Guide Supplement for Seismic Bracing per NFPA 13 April 2020

Anchorage for seismic bracing technical supplement
3
April 2020
Figure 2 — Sway brace load, F
pw
, from typical sway brace configuration (Source: NFPA 13 2016 Edition Figure 9.3.5.12.1)
Horizontal earthquake load design per NFPA-13
The maximum horizontal earthquake load, F
pw
that will not exceed the allowable capacity of the anchor, can be derived from
NFPA 13-16 Eq. A.9.3.5.12.2a:
T
+
V
≤ 1.2
T
allow
V
allow
where:
T = applied service tension load, including the effect of prying = F
pw
x P
r
for all Angle Categories
F
pw
= horizontal earthquake load
P
r
= prying factor based on fitting geometry and brace angle from vertical as determined from NFPA 13-16 A.9.3.5.12.2
T
allow
= allowable service tension load
V = applied service shear load =
Angle Category A, B, and C: V = F
pw
Angle Category D, E, and F:
V =
F
pw
tanθ
Angle Category G, H, and I:
V =
F
pw
sinθ
θ = brace angle (see Figure 2)
V
allow
= allowable service shear load
T/ T
allow
shall not be greater than 1.0
V/ V
allow
shall not be greater than 1.0
Substituting for T and V for the various angle categories:
Angle Category A, B, and C:
F
pw
∙ P
r
+
F
pw
≤ 1.2
T
allow
V
allow
where:
F
pw
∙ P
r
/ T
allow
≤ 1.0
F
pw
/ V
allow
≤ 1.0
Angle Category D, E, and F:
F
pw
∙ P
r
+
F
pw
/ tanθ
≤ 1.2
T
allow
V
allow
where:
F
pw
∙ P
r
/ T
allow
≤ 1.0
(F
pw
/ tanθ) / V
allow
≤ 1.0
Angle Category G, H, and I:
F
pw
∙ P
r
+
F
pw
/ sinθ
≤ 1.2
T
allow
V
allow
where:
F
pw
∙ P
r
/ T
allow
≤ 1.0
(F
pw
/ sinθ) / V
allow
≤ 1.0