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

Anchorage for seismic bracing technical supplement
5
April 2020
Design Example:
We will use a carbon steel 1/2-in. diameter x 3-1/4-in. effective embedment depth Hilti KWIK Bolt TZ (KB-TZ) expansion anchor to
attach a Hilti seismic lateral brace into 3,000 psi normal weight concrete. We will assume the concrete is cracked for the seismic
design. We will assume the anchor is in the middle of a concrete slab (no edge or anchor spacing influence). We will use a Hilti
MQS-SP-L-1/2” seismic hinge with a brace angle of 45 degrees (Angle B) attached to the underside of the concrete. Prying factor
for this specific hinge in angle category B is 1.580.
The LRFD tension and shear capacity of the KB-TZ is determined through a calculation per ACI 318-14 Ch. 17 based on the
design variables from ICC-ES ESR-1917. A design using the Hilti PROFIS Engineering design software yielded the following LRFD
capacities (design is performed in cracked concrete with seismic reduction factors per ACI 318-14 17.2.3.4.4):
T
LRFD
= 2,625 lb.
V
LRFD
= 3,572 lb.
To convert the values to an Allowable Stress Design (ASD) value, multiply the LRFD value by 0.43 (NFPA 13-16 A.9.3.5.12.8.3(D)).
T
allow
= 2,625 ∙ 0.43 = 1,129 lb.
V
allow
= 3,572 ∙ 0.43 = 1,536 lb.
We will calculate a maximum horizontal shear, F
pw
= 585 lb. Thus:
F
pw
∙ P
r
+
F
pw
=
585 ∙ 1.580
+
585
= 1.20 ≤ 1.2 OK
T
allow
V
allow
1,129 1,536
F
pw
∙ P
r
/ T
allow
= 585 ∙ 1.580 / 1,129 = 0.82 ≤ 1.0 OK
F
pw
/ V
allow
= 585 / 1,536 = 0.38 ≤ 1.0 OK
∴ Maximum horizontal load, F
pw
= 585 lb.
Alternatively, the maximum horizontal load, F
pw
, can be determined from the shortcut tables starting on page 7. Going to page 7, F
pw
can be selected as shown (refer to the Hilti MQS-SP-L-1/2” table, using Angle B, for the 1/2x3-1/4 KB-TZ anchor).
Nominal
anchor
dia.
Effective
embed.
Min.
edge
distance
Min.
spacing
distance
Min.
concrete
thickness
Hilti MQS-SP-L-1/2” and MQS-SP-T-1/2”
A B C D E F G H I
30°-44° 45°-59° 60 °-74° 75°-90° 30°-44° 45°-59° 60°-90° 30°-44° 45°-59° 60°-90°
Pr Pr Pr Pr Pr Pr Pr Pr Pr Pr
in in in in in 4.100 1.580 0.870 1.850 1.520 2.320 3.440 3.710 2.620 2.140
1/2
2 4 6 6 135 291 423 260 243 220 161 130 184 225
3-1/4 6-1/2 9-3/4 6 275 585 844 524 485 443 328 261 370 453