Group 5.J Anchorage, Part II: Substrates Flashcards
What are the two design considerations when fastening into a metal base material:
Thick base material or
Thin base material.
It should be determined if the base material is thick enough to take advantage of the full _____strength of the fastener or if the thin base material will result in _______ of the fastener before its tensile strength is reached?
tensile
pull-out
When the base appears thick enough so that the
fastener material will fail in tension before it pulls
out, the base material should still be analyzed to
verify that its _______ & ____ ___ capacity are
greater than the tensile strength of the fasteners.
Bearing and pull-out
The internal stresses in the fastener should
be checked according to the relationship of
tension and shear load in the fastener, as well as
design allowable tension and shear ______ the
fastener.
strength of
if the fastener is subjected to combined shear
and tension load, this relationship _____must hold.
The sum of the squared ratios of [Shear load to Allowable shear] and of [tension load and allowable tension], must be less than or equal to 1.0
(St/Sa)^2 + (Tt/Ta)^2 <= 1.0
Second, the bearing capacity of the substrate
material must be greater than the shear load on
the fastener. And, the point at which the fastener
will pull out of the substrate must also be checked
against the tension in the fastener. That is, these
relationships ______ must be satisfied.
The ratio of V shear load to allowable bearing strength of the substrate and the Tension load and allowable pull out strength, must both be less than 1.0
V/A bng <= 1.0 and T/A pull <= 1.0
Unlike steel or concrete substrates, wood
connections generally experience a slower, ductile
failure called _______
Yielding
Pull-out (or withdrawal) capacity of these fastener
types (such as nails, wood screws, lag screws, bolts and spikes) is dependent on the fastener itself, the
____of penetration, ____ type and one or more
end-use adjustment factors as applicable.
depth, wood
End-use adjustment factors that impact pull out capacity of wood fasteners include:
(8 items)
(These pertain to the time and environmental conditions of the loading, the dimensions and geometry of the fastener and other materials involved.)
LWT PTE MD
- Load Duration Factor
- Wet Service Factor
- Temperature Factor
- Penetration Depth Factor
- Toe-Nail Factor
- End Grain Factor
- Metal Side Plate Factor
- Diaphragm Factor
Additional factors for fastening to wood include:
location and clusters
Edge distance:
Group Action Factor.
Edge distance factor pertains to the the distance of the fastener from the ___ or ___ of the material being anchored and of the substrate.
edge or end
Group Action Factor pertains to the _______ and ______of multiple fasteners in relation to one another.
spacing and pattern
Group Action Factor (Cg) pertains to the _______ and ______of multiple fasteners in relation to one another.
spacing and pattern
When figuring the minimum yield capacity of the
connection, the design professional will have to
analyze up to ____ yield limit equations to determine
the controlling value.
six
Concrete and Masonry:
The two modes of failure of wedge type anchors
are assumed to be _____ ____ failure or _____failure.
The calculated anchor capacity would be based on
the ______ (higher / lower) of these two modes of failure.
anchor bolt failure or substrate failure.
lower
All wedge type post-installed concrete anchors
develop a “cone of influence” based on the
______ of the anchor, _____ of anchor
embedment and strength of the substrate.
Diameter, depth
An anchor’s holding capacity is directly related to the
______of concrete that is included in the “cone of
influence,” around the anchor.
volume
The “cone of influence,” around masonry anchors can be depicted as a line starting from the _____of an anchor and radiating upward at a ___ degree angle to the masonry surface,
bottom
45
Anything that reduces the volume of concrete in
the cone of influence reduces the ______ _____ of
that anchor. This occurs when the cones of influence of adjacent masonry anchors overlap.
holding power
A reduction in holding power of masonry anchors can also occur when an anchor’s cone is cut off by being ______________ of the concrete material.
too close to the edge
Analysts should refer to the fastener manufacturer’s technical data for minimum and maximum ______ along with _______ ____ and allowable loads for masonry anchors
spacings, embedment depth
If no technical data is available, a good rule of
thumb to estimate proper spacing of multiple
anchors is that, where no reduction in holding
capacity occurs, spacing should be equal to ____
anchor diameters.
4
10
8
15
10
A separation of five diameters would reduce holding capacity of a given masonry anchor to ___percent. That can also be expressed as a reduction factor of ____
50%
0.5
Holding capacity reduction factors for separation distances between 5 and 10 bolt diameters can be determined by_________.
interpolation.
1/2” diameter anchors should be placed no closer than 1/2” x ___ (or __ inches.)
1/2” x 10 (or 5 inches)
A good rule of thumb to estimate the minimum distance of an anchor from the EDGE of the concrete
substrate is that, where no reduction in holding
capacity occurs, the edge distance should be at
least __anchor diameters.
12
When the edge distance is equal to ___ anchor diameters, the masonry anchor’s capacity is reduced by 50 percent. That can also be expressed as a reduction factor of 0.5.
six
To provide full capacity, a 1/4” inch diameter anchor should be no closer than one quarter times ___ which equals __ inches from the edge of the concrete substrate.
12, 3
If the fastener manufacturer publishes only
ultimate loads for the product, a safety factor of
____ must be applied to arrive at the design
allowable strength.
four
Allowable strength is the maximum a material can
withstand without ______ , while ultimate
strength is the maximum it can withstand before
______.
deforming, breaking
For groups of anchors, the appropriate factors for
the reduction in holding capacity due to both
_____ and ___ ________ effects on their cones
of influence must be figured for each anchor
spacing and edge distance.
overlapping and edge cutoff
In anchor groups, there are two reduction factors for each anchor:
• Reduction factor for concrete bolts due to
___ ______
• Reduction factor for concrete bolts due to
______
edge distance
spacing
An anchor’s final ______ allowable load is
obtained by multiplying the allowable load by all
the appropriate reduction factors for spacing and
edge distance.
working allowable load
Once the allowable load is arrived at, with appropriate reduction factors applied) the shear or tension load on the fastener is then compared to its allowable load using this equation_______
Pv / Av <= 1.0 or Pt / At <= 1.0
Pt = Tension load in fasteners Pv = Shear load in fasteners
At = design allowable tension for fastener Av = design allowable shear strength for fastener
When anchoring into masonry other than concrete
– such as filled or hollow CMUs, face brick or tile –
not all anchors are designed equally. In fact, these
conditions are all ______ than the anchor,
meaning that the _______ (bolt/substrate) will fail before the ______(bolt/substrate) does.
weaker
Substrate will fail before the bolt
Use only those anchors that the manufacturer has
designed for the specific substrate and for which
the _______ and ______ loads have been
defined.
ultimate and allowable
Spacing between anchors – usually ____
per CMU cell – and edge distances are very critical.
These can vary greatly from manufacturer to
manufacturer and even from anchor to anchor.
one
Threaded concrete anchors follow the same spacing and edge distance guidelines as ___ ____ anchors, even though they may not develop a cone of influence in the same manner as ____ ___fasteners.
Wedge type
wedge-type
Now, wasn’t this fun?
No, it was a miserable slog through numbing pablum
Meh, it was OK.
Yes, the bestest ever!
Yes, the bestest ever!
Quiz Question #1
An anchor manufacturer publishes only ultimate loads f products. What safety factor must be applied to arrive at the design allowable strength of these fasteners?
ten
four
two
one (Ultimate and allowable are the same)
four
Quiz Question #2
1/2” diameter concrete expansion bolts are anchored in concrete to a depth permitting them to develop their full tensile and shear strength. In the absence of the fastener manufacturer’s specification, what is the approximate recommended minimum spacing between the anchors to permit full holding capacity?
2 1/2” inches
5 Inches
7 1/2” inches
10 inches
5 Inches
10 diameters
Quiz Question #3
A 1/4” diameter concrete expansion bolt are anchored in concrete to a depth permitting them to develop their full tensile and shear strength. It is located 1 1/2” from the edge of the concrete in which it is fastened. What percentage of the anchors full capacity should be estimated?
100%
75%
50%
0%
50%
Quiz Question #4
An attachment using a 1/4” diameter concrete expansion bolt must be shimmed 3/4”. This anchor….
needs to be increased in diameter to at least 3/8”
needs to be increased in diameter to at least 1/2”
is sufficient in size for this application
is more than sufficient in size for this application
needs to be increased in diameter to at least 3/8”
Shim space can not be more than 2 bolt diameters
Quiz Question #5
Pull-out failures of fasteners anchored in wood are usually of the ____ type
Shear
pull-over
yield
bending
Yield.