Pullout strength( mechanical anchors only)
Sustained loads and overhead use where:
N pn = ψ m, P × N p
ψ m, P = Pullout cracking factor taken from third-party evaluation report
N p = Basic single anchor pullout strength taken from thirdparty evaluation report
For adhesive anchors that resist sustained tensile loading, Section 3.3.2.5 of AC58 requires an additional calculation be satisfied for the sustained portion of the factored load per ACI 318-19 Section 17.5.2.2 and 17.5.2.2.1. Design of adhesive anchors to resist sustained tension loading shall satisfy the below equation:
0.55Φ N ba, m ≥ N ua, s
Bond strength( adhesive anchors only) where:
N mag =
A Na A Nao
Ψ ec, Na Ψ ed, Na N ba, m
N ua, s = factored sustained tensile load( dead load + any sustained live load) where:
where:
A Na = Projected influence area of single adhesive anchor or group of adhesive anchors, in. 2( 17.6.5.1.1)
A Nao = Projected influence area of a single adhesive anchor if not limited by edge distance or spacing, in. 2( 17.6.5.1.2)
=( 2c Na) 2
c Na = projected distance from center of an anchor shaft on one side of the anchor required to develop the full bond strength of a single adhesive anchor, in.
= 10 d a
T uncr 1, 100
When using the tables presented within this Masonry Anchor Strength Design Guide for the design of adhesive anchors to resist sustained tension loading, sustained loading is calculated by multiplying the value of ФN n or N r by 0.55 and comparing the value to the tension dead load contribution( and any sustained live loads or other loads) of the factored load. Edge, spacing, and masonry thickness influences do not need to be accounted for when evaluating sustained loads.
Shear— Nominal strengths
Steel strength V sa = 0.6 A se, V f uta
where: |
d a = Nominal outside diameter of post-installed anchor, in. |
A se, V = Effective cross-sectional area of an anchor in shear, in. 2 |
т uncr = Characteristic bond stress capacity in uncracked masonry taken from third-party evaluation report, psi
ψ ec, Na = Bond eccentricity factor( 17.6.5.3)
Masonry breakout
ƒ uta = Minimum ultimate tensile strength of anchor, psi
= |
1
1 + e ' N c Na
|
≤ 1.0 |
V mbg = A Vm
A Vmo ψ ec, V, m ψ ed, V, m ψ m, v V b, m
|
ψ ed, Na = Bond edge effect factor( 17.6.5.4) where:
= 1.0 if c a, min ≥ c Na
= 0.7 + 0.3 c a, min c Na if c a, min < c Na
N ba, m = Basic single anchor bond strength, lb = т( cr, uncr), mπ d a hef
A Vm = Projected masonry failure area of a single anchor or group of anchors in shear, in. 2.( 17.7.2.1.1)
A Vmo = Projected masonry failure area of a single anchor in shear if not limited by edge distance or spacing, in. 2( 17.7.2.1.3)
= 4.5( c a1) 2 where: т( cr, uncr), m = Characteristic bond stress capacity in cracked or uncracked masonry, respectively, psi.
Where analysis indicates cracking at service load levels, use т cr, m. Where analysis indicates no cracking at service load levels, use т uncr, m.
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