Aama Tir-A9-2014
Aama Tir-A9-2014
Aama Tir-A9-2014
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AAMA TIR-A9-14
ORIGINALLY PUBLISHED: 1991
PRECEDING DOCUMENT: T1R-A9-91
PUBLISHED: 5/14
Technical information and data assembled in this report were drawn from a number of organizations. The relevant
publications of these organizations are listed under Section 25.0, "Applicable Documents."
Uniform coarse machine threaded fasteners and spaced threaded fasteners are covered in this report. The Unified Thread
Series are generally used in either clear holes with mating nuts or in tapped holes. Thread cutting screws with machine
threads are used to cut their own threads in pre-drilled holes. Spaced threaded fasteners, on the other hand, are generally used
only as tapping screws. This subject is covered in detail in Section 7, 'Fastener Load Tables Commentary.'
Metric fasteners are not addressed in this document, but the design parameters included apply equally well to metric
fasteners. If the user wishes to develop metric fastener load tables, the appropriate loads can be developed using the formulas
provided for each table with appropriate IP to Metric conversions.
Metals used in fasteners, on which the data in this report is based, include various types of carbon steel and stainless steel
alloys. The use of aluminum fasteners is not recommended for cmtain wall anchoring systems and no data on aluminum
fasteners is included. Carbon steel fasteners shall be plated or coated in accordance with the specifications in Section 4,
'Protection Against Corrosion.'
Tables giving allowable tension, shear and bearing loads for a range of different fastener sizes, for carbon steel and stainless
steel alloys, are included in this report. The four sizes at the small end of the size range, in ascending order, are designated
#6-32, #8-32, #10-24 and #12-24. For fasteners designated in this manner the number preceding the hyphen is related to the
fastener diameter. For larger size fasteners the number preceding the hyphen is the nominal diameter in inches and/or a
fraction thereof. The larger size fasteners range from 1/4-20 through 1-8. In both designation systems the number following
the hyphen is the number of threads per inch. Equations needed to calculate the allowable loads are included with the tables.
Section 22.0 of this document addresses the pullout strength of fasteners in aluminum substrates. The data in fastener load
Tables 22.1 to 22.12 was developed empirically using the formulas provided and verified through limited testing.
Please note that Inch-Pound (I.P.) units of measurement are used throughout this document.
The problem with inferior fasteners on the market has been serious during the past few years. Many fasteners may be found
to be substandard mechanically and dimensionally when checked even though marked as high performance grades. Protective
coatings on fasteners may also be a problem. As a result of more stringent environmental requirements and tightening
economic pressures, fewer manufacturers are applying adequate coatings. The quality and thickness of protective coatings in
today's market, particularly on low price fasteners, is somewhat unreuable. In order to be certain that the fastener needed to
meet design criteria is provided, the designer must not only specify fastener size and type, he must also specify material,
minimum mechanical properties, thickness and type of protective coating required. See the suggested Fastener Specification
Checklist, Section 13.0, for items to be included in fastener specifications.
This concern became so serious in the l 980's that the United States Congress passed the Fastener Quality Act (FQA) in 1990
and amended the FQA in 1999 to address fastener quality. This Fe·deral law was enacted to protect the public safety where
citizens were at risk due to faulty fasteners. However, the FQA covers only bolts, nuts, screws, studs and load indicating
washers of Y." diameter or greater or those requiring a grade mark. Products exempt from this act are those which are
produced under a recognized Quality Assurance Program such as ISO 9000. The user should consider adding this
requirement to all fastener specifications.
ASTM standards give the chemical and mechanical requirements for the steels used in fasteners. In addition, they set forth
requirements which the purchaser of fasteners may specify for the quality control procedures to be followed in connection
with his order. These include shipment lot testing, source inspection, alloy control, heat control, permeability, manufacturer's
identification and material identification. ASTM F606 sets forth in detail the test methods for determining the mechanical
properties of externally and internally threaded fasteners. Appropriate reference to these standards can provide the basis for
reliable quality assurance programs.
Stainless steel fasteners come in a variety of alloy types. All stainless steel alloys referenced in this report have good
resistance to corrosion. However, some of these alloys have better resistance than others. Type 316, for example, has a higher
resistance than Type 304. Specifying the higher resistance and types of stainless steel for all fasteners does not address all
concerns with corrosion. Some fastener designs are not manufactured in all types of stainless steel because of the need for
hardening heads or points, or because of the capacities of the screw machines used to manufacture fasteners. The higher
resistance types of stainless steel generally cannot have the finishes applied which match anodized framing without resorting
to painting. Painting of screw heads is expensive and of dubious durability. Many types of fasteners are only available in
stainless steels having lower resistance to corrosion. Small order quantities, less than 100,000 fasteners per run, may also
limit the availability of the fastener desired or greatly increase its cost. The specifier and purchaser must be aware of these
matters and make the best compromise possible, all factors considered, in the selection of the fasteners.
Carbon steel fasteners may be plated with zinc, cadmium, nickel or chromium to provide adequate resistance to corrosion.
The severity of the service conditions, to which the fasteners will be exposed, must be considered in the specification. For
zinc and cadmium coatings the following specifications are recommended: (The specifier should select one or more
requirements as appropriate.)
Zinc plated fasteners shall meet the requirements of ASTM B633 for Class FE/ZN 5, 5µm coating thickness, service
condition SC 1 (mild), with Type III finish meeting corrosion resistance requirements after a 12-hour salt spray test.
Zinc plated fasteners shall meet the requirements of ASTM B633 for Class FE/ZN 8, 8µm coating thickness, service
condition SC 2 (moderate), with Type rr finish meeting corrosion resistance requirements after a 96-hour salt spray test.
Mechanically deposited zinc coated fasteners shall meet the requirements of ASTM B695 for Class 5 coating, 5 µm thick
with Type II finish, or Class 8 coating, 8 µm thick with Type II finish. Both Class 5 and Class 8 coatings shall meet the
corrosion resistance requirements after a 72-hour salt spray test. (Thicker coatings meeting this ASTM standard are available
if required.)
Cadmium plated fasteners shall meet the requirements of ASTM B766 for Class 5, 5 µm thick, Type III coating meeting
corrosion resistance requirements after a 12-hour salt spray test.
Cadmium plated fasteners shall meet the requirements of ASTM B766 for Class 8, 8 µm thick, Type II coating meeting
corrosion resistance requirements after a 96-hour salt spray test.
Mechanically deposited cadmium coated fasteners shall meet the requirements of ASTM B696 for Class 5 coating, 5 µm
thick with Type II finish, or Class 8 coating, 8 µm thick with Type 11 finish. Class 5 coatings with Type II finish shall meet
the corrosion resistance requirements after a 72-hour salt spray test. Class 8 coatings with Type II finish shall meet the
corrosion resistance requirements after a 96-hour salt spray test. (12 µm) coatings meeting this ASTM standard are available
if required.)
An advantage of mechanical deposition is that it does not p-roduce hydrogen embrittlement in hardened steel during the
coating process.
Type II and Type III finishes for zinc and cadmium receive supplementary colored chromate treatments. These
supplementary treatments produce a bright or semi-bright continuous, protective conversion coating of uniform color which
retards the formation of white corrosion products caused by exposure to stagnant water, moist atmosphere or stagnant
environments containing organic vapors. Colors produced can range from yellow through bronze and olive-drab to brown
and black. The salt spray test used to evaluate these treatments shall be conducted in accordance with ASTM B201.
The perfom1a11ce of both zinc and cadmium coatings depends largely on their coating thickness and the kind of environment
to which they are exposed. Without proof of satisfactory correlation, accelerated tests such as the salt spray test, cannot be
relied upon to predict performance in other environments, nor will the tests serve as comparative measures of the corrosion
protection afforded by the two different metals. Thus the superiority shown by cadmium coatings over zinc coatings of equal
thickness in the standard salt spray test cannot be construed as proof that this will hold true in all atmospheric environments.
The following specification is recommended for nickel or chrome plated fasteners: Nickel or chromium plated fasteners shall
meet the requirements of ASTM B456.
Zinc coatings may also be applied by the hot-dip process (Galvanizing). For such coatings the following specifications are
reconunended:
Zinc coating applied by the hot-dip process shall meet the requirements of ASTM Al53. For Class C hardware, which
includes threaded fasteners over 9 nun (3/8 in) in diameter, minimum weight of coating on surface, 40 mg/cm2 (1.25 oz/ft2)
For Class D hardware, which includes threaded fasteners 9 mm (3/8 in) and under in diameter, minimum weight of coating
on surface, 30 mg/cm2 (1.00 oz/ft:2).
Based on mathematical calculations, 30 mg/cm2 (1.00 oz/ft:2) corresponds to an average thickness of0.04 mm (1.7 mil).
Hydrogen Embrittlement is a condition of low ductility in metals resulting from the absorption of hydrogen, which may be
absorbed during the manufacturing process. Bolts and screws, with a hardness ofC35 or greater on the Rockwell C scale, are
particularly subject to embrittlement if hydrogen is permitted to remain in the steel and the steel is subjected to sufficient
tensile stress. This hardness range is typically associated with a tensile strength of 150 ksi or greater. The hazard caused by
hydrogen embrittlement is the unpredictable failure, which may occur, of a fastener under tensile load. Results ofsuch failure
could be disastrous. A sufficiently high tensile load can result when headed fasteners are tightened, especially if a drill or
power wrench is used in the tightening process.
Acid pickling and alkaline cleaning prior to the application of protective metallic coatings generate hydrogen which can be
absorbed in the fasteners and ifnot removed can be trapped by the coatings. Also, hydrogen as a by-product of electroplating
can be generated and trapped in the plating.
The mechanism ofhydrogen embrittlement failure is believed to be due to the migration ofhydrogen into microscopic cracks
when a sufficient load is applied to a fastener. This causes internal pressures and microscopic ruptures in the stressed areas.
This action continues under repeated or constant high tension loads and eventually leads to a failure of the fastener. Hydrogen
embrittlement is non-corrosion related and is often mistaken as the cause of failure when a corrosion process is active and the
true cause offailure is hydrogen-assisted stress-corrosion cracking.
For hot-dip galvanized steel fasteners, hydrogen can be absorbed during the pickling process. Heating to I50°C (300 °F) after
pickling and before galvanizing, in most cases, results in expulsion of the hydrogen absorbed during pickling. Reference may
be made to ASTM Al43 for more information on the subject ofembrittlement ofhot dip galvanized structural steel products.
Jn practice, hydrogen embrittlement of galvanized steel is usually ofconcern only if the steel exceeds approximately 150 ksi
in ultimate tensile strength. ASTM provides specifications for galvanizing A 325 bolts but galvanizing of A 490 bolts is not
permitted.
Stress Corrosion is the effect of corrosion on a metal which is under stress. When metals are under stress the effect of
corrosion can be much more severe than when metals are not stressed. This is true for metals subjected to constant high
tension stresses as well as for metals subjected to cycling stresses which cause fatigue. Stress corrosion failures can occur
shortly after the load is applied but may not occur for months or years later. Such failures occur without warning. It is
believed that when corrosion occurs microscopic cracks develop in the high stress areas. The combined effects of stress and
corrosion cause the crack to grow inwardly which reduces the cross-sectional area. Eventually, when the cross-sectional area
can no longer support the load, the fastener breaks. The rate offailure depends on the level of stress, the corrosive conditions
and the metallurgical properties of the fasteners.
Hydrogen-Assisted Stress-Corrosion Cracking (HASCC) is similar to stress-corrosion cracking. HASCC takes place when
stress-corrosion cracking is accelerated by the presence of hydrogen which is generated in a service application. Hydrogen
generation may be due to a galvanic couple, for example, between aluminum and iron in the presence of water. Even
fasteners which might resist stress-corrosion cracking alone can fail ifservice-generated hydrogen is diffused into the surface
of the fastener. Sufficient tension stress for HASCC may be caused by normal tightening of the fastener during installation.
The Specification for Aluminum Structures (2005 and 2010 editions) requires that bolt and tapping screw materials, for
coated carbon steel, have hardness less than Rockwell C35. Only certain types ofstainless steel ( e.g., 300 series and at least
one particular type, which meets a chromium content criterion, in the 400 series) are permitted for fasteners that are to be
installed in aluminum. These provisions are intended to avoid the occurrence ofHASCC.
Stress Embrittlement is similar to hydrogen embrittlement and, like hydrogen embrittlement, it is non-corrosion related.
Hydrogen generated through the service environment, not in manufacture, causes stress embrittlement. For example,
hydrogen can be absorbed into the surface of an uncoated fastener when caustic substances, such as soap and detergents,
come in contact with nitrates and silicates. Metals most susceptible to stress embrittlement are steels heat-treated to high
strength levels and with high carbon content. In carbon steel fasteners, the higher the hardness, the greater the chance of
stress corrosion, hydrogen embrittlement and stress embrittlement. Hydrogen-assisted stress-corrosion cracking (HASCC)
may occur if an installed (tightened) fastener's hardness equals or exceeds Rockwell C35 and the fastener is in contact with
aluminum in the presence ofmoisture.
This review of hydrogen embrittlement, stress corrosion, hydrogen-assisted stress-corrosion cracking and stress
embrittlement has been presented to point out how dangerous failures may occur in high strength steel fasteners. Hardened,
high strength fasteners with a Rockwell hardness of C35 and greater are most susceptible. This hardness range is often
associated with tensile strengths of 150 ksi and greater. Reliable fasteners depend on carefully controlled manufacturing
processes which reduce to a minimum the chance of hydrogen embrittlement. Designs for curtain wall anchoring systems
must take into account the stresses for which fasteners must be selected and the coatings to be employed in order to eliminate
problems due to galvanic action and stress corrosion. ASTM standards and technical literature of reputable manufacturers
provide valuable information on these subjects.
Other significant factors, described in the following paragraphs, must be taken into consideration when galvanized high
strength bolts and nuts are to be used.
Reduction of Mechanical Properties. The heat treatment temperatures for certain types of high-strength bolts, Type 2 A 325
for example, is in the range of the molten zinc temperatures for hot-dip galvanizing, and, therefore, there is a potential for
diminishing the heat treated mechanical properties by the galvanizing process. For this reason, AISC Specifications require
that such fasteners be tension tested after galvanizing to check the mechanical properties.
Nut Stripping Strength. Hot-dip galvanizing affects the stripping strength of the nut/bolt assembly because to accommodate
the relatively thick zinc coating on bolt threads it is usual practice to tap the nut oversize. This overtapping results in a
reduction in the amount of engagement between the steel portions of the male and female threads with a consequent
approximate 25% reduction in stripping strength. Only the stronger hardened nuts have adequate strength to meet
specification requirements with the reduction due to over-tapping.
Torque Involved in Tightening. Hot-dip galvanizing both increases the friction between the bolt and nut threads and also
makes the torque induced tension much more variable. Lower torque and more consistent results are provided if the nuts are
lubricated. Refer to ASTM A325 for specifications and ASTM A563 for testing requirements.
Shipping Requirements. Galvanized bolts and nuts are to be treated as assemblies and shipped together. Purchase of
galvanized bolts and galvanized nuts from separate sources is not recommended because the amount of over-tapping
appropriate for the bolt and the testing and application oflubricant would cease to be under the control of a single supplier. In
that case the responsibility for proper perfonnance of the nut/bolt assembly would become obscure.
5.0 PREVENTION OF FASTENER LOOSENING
There are many devices designed to keep the fasteners commonly used in curtain wall framing from loosening or turning out
due to thermal movements, building movements, wind forces or vibration. Those commonly used are the various types of
lock washers including pyramidal, internal tooth, external tooth, helical spring, serrated flanges and SEMS assemblies. Also
used, to a lesser degree, are locking devices or methods such as nylon patches, plastic screw inserts, nylon insert lock nuts,
thread locking compound, distorted threads, and dissimilar numbers of threads per inch for fasteners and their nuts or tapped
holes. These devices can effectively prevent loosening of fasteners due to building movements and vibration induced by wind
or other causes. Appropriate devices should be selected for the specific applications in which they will be used.
Another important criterion for choosing a locking device is its torque limiting ability. Where fasteners are used in extruded
aluminum screw chases there is a tendency for the threads in the aluminum to strip if too much torque is applied to the steel
fastener. However, if a lock washer is used, especially a toothed lock washer, the friction between the steel washer teeth and
the softer aluminum surface is usually great enough to cause the fastener to tighten before stripping of the aluminum chase
occurs. If a torque specification is given for a particular fastener application, it is important that the specification be followed
to prevent stripping.
Not all fasteners in a framing system require locking devices to resist vibration or torque Limiting devices. Generally those
fasteners which would be considered main structural fasteners or anchors in curtain wall applications, and those which attach
moving parts to the framing require the consideration of these types of devices. Fasteners which hold shear blocks in place,
perimeter fasteners for windows and storefronts and those which hold light trim in place do not require locking or torque
limiting devices.
The sources of fastener vibration are basically two: wind and machinery. Vibrations induced by changes in wind pressure
tend to be of low amplitude and rather long cycle times. Vibrations induced by machinery will tend to be of greater amplitude
and of much higher frequency. Most curtain wall framing applications do not encounter vibration sources other than those
induced by the wind. Machinery induced vibrations, though of infrequent occurrence, are serious in nature and should be
carefully analyzed. It will be assumed that only wind induced vibrations occur in the framing connections described herein.
A safety factor is used in the Allowable Strength Design (ASD) method. This method was used to determine the allowable
values presented in this document. There is also another design method, termed the Load and Resistance Factor Design
(LRFD) method. In LRFD, the combined use of a load factor m (greater than 1) and a resistance factor <p (less than 1) is the
equivalent of using a safety factor. That is, SF = m/cp. Load factors are given in the governing building code. Resistance
factors, also termed strength-reduction or capacity factors, are given in the specification for the structural
material/components being connected. Currently, some specifications present design rules using both methods, but other
specifications use only one of tbe methods.
For fasteners of 1/4" or less in diameter, SF equal to 3.0 has been used in thisTIR to generate allowable values.This value is
used in both the North American Specification for Cold-formed Steel Structures (2007 and 2001) and the 2010 Specification
for Aluminum Structures for this size range of tapping screws. This value exceeds the largest implicit value (2.20) for at least
some fasteners, in this size range, that are addressed by the Specification/or Cold-formed Stainless Steel Structural Members
(ASCE 8). Both annealed and cold-worked conditions were evaluated. The value of 2.20 occurs for the annealed condition
and assumes a load factor of 1.6.
It is noted that design provisions for tapping screws (1/4" maximum diameter) first appeared in editions of the first two of the
above standards that were published after the first (1991) edition ofTIR A9, which used Sp equal to 2.5. Hence the allowable
values in the presentTIR, for this size range, are less than in the 1991 edition.
For fastener diameters that exceed 1/4", but are less than or equal to l ", the presentTIR uses a Sp equal to 2.5.This equals or
exceeds safety factors associated with the standards that were studied. For the range from 0.25" to less than 0.5", there is
limited guidance available in the reviewed standards. The largest value (2.40) determined is based on the stainless-steel
specification. It is for the annealed condition and a load factor of 1.6.
For diameters from 0.5" to I", the aluminum specification uses Sp= 2.34 for aluminum bolts. For implicit safety factors, the
cold-formed steel specification and the stainless-steel specification use maximum values of 2.31 and 2.42, respectively.The
AISC steel specification (Specification for Structural Steel Buildings; 2010) uses a nominal safety factor, designated as n,
equal to 2.0. This is a nominal value because the fasteners' nominal strength values are based on gross cross-section area
rather than tensile or root area, for tension and shear respectively. Note that the cold-formed steel specification also uses
gross areas. Because of this design simplification, the "true" value of the safety factor varies with the fastener diameter and
type of load (tension or shear).
To determine more accurate values of safety factor for each bolt diameter, the minimum-ultimate tension strengths for each
of several bolt types (A307, A325, A449 and A490) were calculated using tensile areas and AISC material properties.These
values were then divided by the corresponding allowable values based on the AISC procedure. Shear values were also
computed.The ultimate-to-allowable ratios (Sp) constitute more accurate values of the safety factors. For most diameters, the
ratios did not equal 2.0.The values of Sp range from 1.92 for 0.5'' diameter (A490, tension) in the 2005 edition to 2.48 for 1"
diameter (A307, shear) in the 1989 edition. Although the 1989 edition did not use n, it did use gross areas and allowable
stresses.
For shear, in addition to use of root areas, the ultimate shear stress for each material (fasteners and tapped materials) was
approximated by (Fru /,/3). This is equal to about 0.577 Fru , where Fru is the minimum tensile strength of the given
material. The ratio of root area to tensile area varies from 0.911 to 0.929 for UNC fasteners with diameters of 0.5" to 1".
Using 0.75" diameter as an example, 0.577 (0.924) equals 0.533.This is the ratio of the fastener's shear strength to its tensile
strength. This value agrees with the ratio of shear to tension strengths (nominal stresses), for threads in the shear plane, for
values in the AISC specification (2005).
For fasteners with diameters from 0.5'' to l ", given the range of "true"· Sp values for the bolts in the AISC specification and in
other specifications, it was decided to select one value of Sp that would equal or exceed all of the "true" values. This is a
conservative approach for this TIR that simplified the calculation procedure and permitted the use of a consistent method
(using tensile and root areas) of determining allowable values for a broad range of fastener diameters and material types, and
several types of connected materials.
7.0 FASTENER LOAD TABLES COMMENTARY
Fastener Load Tables provide numerical values for evaluating the loaded performance of threaded fasteners of various metals
and range of sizes. The performance (e.g., structural design) of the metal components being connected must be detennined
separately, except for items (e.g. bearing) included in the tables and other sections of the TIR. The values given are for
quality fasteners in round clearance holes or tapped holes as noted. When specifying fasteners, the designer, in addition to
specifying loaded performance, must specify fastener quality, corrosion resistance and minimum mechanical properties.
Specification of these items is usually done by appropriate reference to ASTM or other recognized standards. It is the
responsibility of the designer/engineer/architect to determine the availability of fasteners.
The two general types of fasteners described in this report have either machine threads or spaced threads. The thread angle of
both types of threads is 60 degrees. Machine threaded fasteners have threads which are closely spaced in accordance with the
diameter/pitch combinations of the Unified Coarse Thread Series (UNC), as shown in Figures 7.1 (external threads), 13.2
(external threads) and 13.3 (internal threads). The form of Unified Threads is specified in ANSI/ASME Bl.I, Unified Inch
Screws Threads (UN and UNR Forms). Fasteners with spaced threads, as shown in Figure 7.2, have an expanded thread pitch
which results in the spaced threaded fastener having fewer threads per inch than a fastener with machine threads of the same
diameter.
Unified Coarse Machine Threaded Fasteners (UNC) are generally used in either clear holes with mating nuts or in tapped
holes. Thread cutting screws with machine threads are used to cut their own threads in pre-drilled holes. These screws carry
tensile and/or shear loads. Spaced threaded fasteners are generally used only as tapping screws. Most thread forming screws
and some thread cutting screws have spaced threads. Like fasteners with machined threads, these fasteners carry tensile
and/or shear loads. However, due to the smaller number of threads per inch, spaced threaded fasteners have smaller effective
tensile and shear areas than machine threaded fasteners of the same nominal diameter. Also, for a given length of external
and internal thread engagement, fewer threads will resist fastener tension. This in turn means that a spaced threaded fastener
will, in many cases, have lower pullout resistance than a comparable fastener with machine threads. However, this is not
always true for thin materials. To provide conservative values, the allowable tensile and shear strengths for fasteners with
spaced threads are based on a minimum cross-sectional area. This area is found by using the minimum minor diameter (root
diameter) and neglects any additional strength provided by the threads.
The following equations are used to determine the values shown within Tables 20.1 through 20.13.
Nominal Thread Diameter (D) values, for major diameter, are b ased on IFI Fastener Standards tables for both UNC and
spaced thread fasteners.
Tensile Stress Area A(S) for UNC Threads is based on a diameter approximately midway between the pitch diameter and
minor diameter.
Thread Root Area A(R) and the Tensile Stress Area A(S) for Spaced Thread use the basic minor diameter (K) in both
equations.
(7.4) TA = A(S)Fr
(7.5) VA = A(R)Fv
Allowable Bearing values for UNC and Spaced Thread fasteners are based in part on the steel or aluminum bearing ultimate
values of the connection or base material divided by the appropriate safety factor. Reference Section 8.0 for bearing
equations for both steel and aluminum.
The tapped material thickness needed to develop the allowable tensile capacity ofUNC and spaced thread fasteners, as shown
in Tables 20.1 through 20.13 is based on the largest thickness as governed by equations for the internal thread strength of the
tapped material or external thread strength of the fastener. Internal thread strength is determined by the lesser of: 1) pull-out
values (for thin, medium (transition) or thick material, as applicable) or 2) 0.75 shear yield of internal threads. External
thread strength for the fastener is the lesser of: 1) the thread's shear ultimate (thread stripping strength) divided by the safety
factor or 2) 0.75 shear yield of external threads. Equations use TSA(I), TSA(E), and N. By solving the equations (see Section
I 0.0) for thickness (t) and setting PA equal to the fastener's basic allowable tension TA , the equations, in Section I0.0, provide
the minimum thickness (t = tM ) of tapped material that is needed to develop TA , based on internal and external-thread
strength. Note that, typically, the length of thread engagement L 8 must equal or exceed tM. The greater value of tM, based on
internal and external thread strengths, governs. Reference Section I 0.0 for a more detailed explanation of pullout and of thin,
medium (transition) and thick material.
Maximum Tensile Load values, for Available 3/8" Plate Thickness, for both steel {A36) and aluminum (6063-T5 and 6063-
T6), are based on the least of: 1) the basic allowable tension for each fastener, 2) the allowable pull-out value of the internal
thread tapped material, and 3) the allowable value for the external fastener thread. Reference Section 10.0 and Section 21.0
for additional information.
Fasteners subjected to combined tensile and shear loads are limited by the below interaction equation, which applies to all
fasteners regardless of size. Reference Section 11.0 and the Cold Formed Steel Specification for additional interaction
considerations for fasteners installed in thin (t � 3/16 ") steel.
rH=0.866P
z
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. :�.
.
:�,19·�_o". i°A�··� �t�rv2·:-�. - ·. ·._··-�-
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8.1.1 BOLTS
8.1.1.1 Per the cold-formed steel specification, the allowable force PA8 for bolt bearing is:
This is for cases where bolt-hole deformation is not a consideration. For allowable stress design, n = 2.5 for bolts. For the
case of dft < 10, C = 3.0. This applies to all of the fastener sizes in the tables, for t =0.125". For no washer, or only one
washer, in a single shear connection (or outer plies of double shear connections), mp = 0.75. Thus:
This equation was used to generate the table values for bearing on steel. It applies when the edge distance (e), in the load
direction, is at least 1.8 d. For the above values of C and mp , it produces a somewhat lower value (about 5% lower) than the
equation for bolt-hole deformation considered. If dft c 10, the value of C is less than 3, and can be as low as 1.8 for large
d/t· For some conditions, such as a washer at both the head and nut, and/or the inside sheet of a double shear connection, an
mp value larger than 0.75 is permitted. Refer to the cold-formed steel specification for details.
For 1.8 d > e c 1.5 d, the allowable bolt bearing (PA85) is limited by edge distance (e) from center ofa standard hole to the
nearest edge ofthe connected part, in the load direction. The factor fl equals 2.0. The equation is:
Note that if e equals 1.8 d, then PABE equals PA8 in Eq. 8.2.
8.1.2 SCREWS
8.1.2.1 For tapping screws, for which Q equals 3.0 and the edge distance (center of screw to edge of part, in load direction) is
at least 2.7d, the allowable bearing PAs is given by:
This is the same equation as allowable bearing for bolts. Thus the table values for bearing on 1/8" thick steel apply to both
bolts (with nuts) that are installed in clear holes and to screws that are installed into tapped holes (no nuts) in a connected
component.
For screws with edge distance e (in the direction ofload) less than 2.7 d, but c 1.5 d, the allowable bearing is:
For shear-loaded screws in tapped holes, another possible failure mode is screw tilting. This limit state is to be considered if
t2/c < 2.5, where t2 is the thickness ofthe component not in contact with the head. The tilting equation is:
1
8.1.2.3 If conditions differ from those described in the foregoing paragraphs, reference should be made to Sections E3 (bolts)
and E4 (screws), and the Appendix, of the 2007 edition of the North American Specification for the Design of Cold-Formed
Steel Structural Members (AISI) for the procedures to be followed in determining the allowable bearing strength, minimum
spacing and minimum edge distances. Refer also to Supplement No. 2 (2010).
8.2 Allowable Bearing at Bolt Holes for Steel (thickness > 3/16")
8.2.J BOLTS
8.2.1.1 Per the AISC specification, the following equations provide the allowable bearing load PA8 based on the projected
area of bolts in shear connections with the clear distance Le (in the force direction, between edge of hole and edge of part or
of adjacent hole) not less than 2.0d, unless noted otherwise. The value of Q is 2.0.
The following equation, for connections where deformation at service load is a design consideration, applies to standard,
oversized or short-slotted holes (independent of loading direction), and to long-slotted holes (in a slip-critical connection; see
AISC specification) with load parallel to slot length:
In long-slotted holes with the slot's length perpendicular to the direction of the load:
The above equations apply only if Le, in the load direction, is at least equal to 2.0d. Note that allowable bearing values are
less for Le < 2 d than for connections where Le � 2 d . If clear distance Le < 2 d, but Le is greater than the minimum,
then the following equations apply.
For bolts (in standard, oversized or short-slotted holes) for which Le < 2d:
TABLES.I
If deformation around a hole is not a design consideration, oversized and slotted holes are involved, edge distances smaller
than tabulated minimums are proposed and/or conditions differ from those described in the foregoing paragraphs, reference
should be made to Section J3 (bolts) of the 2010 edition of the Specification/or Structural Steel Buildings (AISC) for washer
requirements and/or the procedures to be followed in determining the allowable bearing strength, minimum spacing and
minimum edge distances.
8.3.1 BOLTS
For bolts connecting aluminum components, the allowable bolt-bearing load PA8 for standard round holes is given in the
following equation. This value shall be used for an edge distance (eA ) of2d or greater, where eA is the distance from the
bolt's center to the edge of the connected part. The value of Q is 1.95.
For edge distances (eA ) less than 2d, but� 1.5 d, the allowable bearing load is:
(8.12)
This allowable load is equal to 2/3 of the allowable bearing for bolts in standard round holes. The clear distance Le (edge of
part to the near edge of slot; perpendicular to the slot length) and the slot length are both to be sized so as to avoid over
stressing the aluminum between the slot and the part's edge.
8.3.2 SCREWS
For bearing of tapping screws joining aluminum components, for which Q equals 3 .0, the allowable bearing PAs is:
For the above equation, which was used to generate aluminum-bearing values in the load tables, the edge distance eA (screw
center to edge of connected part) is greater than or equal to 2d. Note that this equation, for screws in tapped holes, produces a
lower value than the equation for allowable bolt bearing, for bolts wiith nuts.
If the edge distance (eA) is less than 2d, but� 1.5d, then the allowable bearing is:
(8.15) PAs = t eA Fru /Q = 0.333 t eA Fru
Screw tilting is also a potential failure mode for shear-loaded screws in tapped holes, where t1 s; t2 and t2 is the thickness of
the part not in contact with the screw head. The allowable load PAsr for tilting is:
(8.16)
If tzft 1 s; 1.0, then allowable shear is the least of the values based on fastener strength, tilting and bearing (for each of the
connected thicknesses). Based on calculations, tilting does not govern for the case of d s; 0.5'' and t2 � 1/8". For t 2 =
1/8" and d� 0.5625", the equations indicate that allowable shear is governed by screw tilting rather than bearing. For
d s; 1" and t 2 < 1/8", tilting may govern (calculation is needed), but the specification addresses only d s; 0.25".
8.3.3.3 For further information on allowable bearing strengths, spacing and edge distances, refer to Sections J3 (bolts) and J5
(screws) in the 2010 edition of Specification for Aluminum Structures (AA). Minimum tensile strengths for a number of
aluminum alloy-tempers can be found in Tables 22. l to 22.12. For fasteners located within I" of a weld, refer to the ADM
for reduced values of Fru for the welded aluminum part.
9.0 STANDARD AND SLOTTED BOLT HOLES
9.1 STEEL (t � 3/16")
It is recommended that holes for bolts not exceed the sizes specified in Table 9.1 (Table 1 in reference) for friction
connections. Slots longer than these dimensions may be used for expansion or anchor alignment purposes with appropriate
engineering analysis or testing.
1 1 1
< 1/2
d+ 3 d+- (d + 3\) by ( d + �) (d + 3 2 ) by ( 2 to 2 n d
2 16
� 1/2
d+
1
6
1
d+-
8
1 1
(d + 3 ) by (d + {)
2
(d + t6) by ( 2 to 2 D d
Standard holes shall be used in bolted connections, except that oversized and slotted holes may be used as approved by the
designer. The length of slotted holes shall be normal to the direction of the shear load. Washers or back-up plates shall be
installed over oversized or short-slotted holes in an outer ply unless suitable performance is demonstrated by load tests in
accordance with Section F of AISI S 100-2007 specification entitled, "North American Specification for the Design of Cold
Formed Steel Structural Members," 2007 Edition.
Hole Dimensions
Bolt
Standard Oversize Short-Slot Long-Slot
Diameter, in.
(Dia.) ffiia.) (Width x Len2th) (Width X Len2th)
1/2 9/16 5/8 9/16 X 11/16 9/16 X 11/4
5/8 11/16 13/16 11/16 X 7/8 11/16 X 19/16
3/4 13/16 15/16 13/16 X 1 13/16 X 17/8
7/8 15/16 11/16 15/16 X 11/8 15/16 X 23/16
1 l 1/16 11/4 11/16 X 15/16 l 1/16 X 21/2
> l 1/8 d+ 1/16 d+ 5/16 (d + 1/16) X (d + 3/8) (d + 1/16) X (2.5 X d)
Standard holes or short-slotted holes transverse to the direction of the load shall be provided in accordance with the
provisions of this specification, unless oversized holes, short-slotted holes parallel lo the load, or long-slotted holes are
approved by the engineer of record. Finger shims up to � in. (6 mm) are permitted in slip-critical connections designed on
the basis of standard holes without reducing the nominal shear strength of the fastener to that specified for slotted holes.
Oversized holes are permitted n any or all plies of slip-critical connections, but they shall not be used in bearing-type
connections. Hardened washers shall be installed over oversized holes in an outer ply.
When Group B bolts over 1 in. (25 mm) in diameter are used in slotted or oversized holes in external plies, a single hardened
washer conforming to ASTM F436, except with 5/16-in. (8 mm) minimum thickness, shall be used in lieu of the standard
washer.
USER NOTE: Washer requirements are provided in the RCSC Specification, Section 6.
Long-slotted holes are permitted in only one of the connected parts of either a slip-critical or bearing-type connection at an
individual faying surface. Long-slotted holes are permitted without regard to direction of loading in slip-critical connections,
but shall be normal to the direction of load in bearing-type connections. Where long-slotted holes are used in an outer ply,
plate washers, or a continuous bar with standard holes, having a size sufficient to completely cover the slot after installation,
shall be provided. In high-strength bolted connections, such plate washers or continuous bars shall be not less than 5/J 6in.
(8 mm) thick and shall be of structural grade material, but need not be hardened. Ifhardened washers are required for use of
high-strength bolts, the hardened washers shall be placed over the outer surface ofthe plate washer or bar.
9.3 ALUMINUM
The aluminum specification does not provide a table ofhole diameters and slot dimensions, but there are some provisions.
Nominal diameter of bolt holes is to be no more than 1/16" larger than the nominal bolt diameter, unless slip-critical
connections are used. Nominal slot width for bolts is to be no more than 1/16" greater than nominal bolt diameter. Jfthe
nominal slot length exceeds 2.5d and/or the edge distance (bolt center lo part edge) is less than 2d, then the edge distance
(perpendicular to slot length) and the slot length are to be sized so as to avoid over stress in the aluminum along the slot. Slot
length is to be perpendicular to the force, unless slip-critical connections are desired.
For screws, the nominal diameter of clear holes is to be no more than 1/16" larger than nominal screw diameter. For threaded
(pilot) holes, see Tables 21.1 to 21.7. For screw pull-over meeting Eq. 11.2, smaller (tighter) clear holes are required. Refer
to Table 11.1.
10.0 PULL-OUT STRENGTH
The allowable pull-out strength (PA ), for a threaded fastener (screw) installed in a tapped hole, must equal or exceed the
design tension force for each fastener used in a tension connection. Allowable pull-out strength depends on the mechanical
properties of the fastener metal and the tapped-component metal including the allowable shear stress for each metal
(considering alloy and, where applicable, the temper), the fastener diameter (d) and number of threads per inch (n), the
internal and external thread-stripping areas (A rs, and A rsE respectively), the length of engagement (L E ) of the external thread
with the internal thread, and the safety factor (Sp ). Refer to Table 20.1 for dimensional information on Unified Coarse
Threads.
Although the internal-thread strength (yield or ultimate), for the steel and aluminum materials considered in this Tffi., governs
in more cases than the fastener's external-thread strength, both need to be evaluated. The design value of stripping area, for
both UNC and spaced external-threads, is typically significantly less than that of the corresponding internal threads. For
external and internal thread-stripping areas for UNC threads, see Table 20.1. Thus internal-thread strength controls (i.e., is
less than external-thread strength) only if the fastener material's yield and ultimate stresses are sufficiently high, compared to
the internal-thread material, to compensate for the external threads' smaller stripping area.
If the engagement length is equal to the thickness, then L E = t. Ford � 1/4",SF equals 3.0. Ford � 5/ 16", Sp equals
2.5.
Fsu is the shear ultimate strength for aluminum. Values of Fsu for various alloy-tempers are given in Table A.3.4 of Part 1 of
The Aluminum Association's "Aluminum Design Manual". For the purposes of this TIR, values for Fsu , for both aluminum
and steel, are conservatively based on Fsu = Fru /,/3, where Fru is the tensile ultimate.
Both ultimate-strength and yield-strength criteria have been considered in determining each fastener's basic allowable tension
and allowable external-thread strengths, as well as the tapped material's allowable internal-thread strength. The following
equations relate the yield-based and ultimate-based allowable stress values, for shear (thread stripping and fastener cross
section) and tension, respectively:
(JO.I)
Solving each of the above equations, for the ratio of yield to ultimate, results in the same equation:
Thus, for Sp equal to 3.0, if the yield-to-ultimate ratio is greater than 0.4444, then the allowable stress value is generally
governed by ultimate strength. Similarly, for Sp equal to 2.5, ultimate strength generally governs the allowable stress value if
FryI Fru exceeds 0.5333. However, for pull-out from "thin" aluminum, the allowable value based on the tapped aluminum
depends on yield, regardless of the Frrf Fru ratio of the aluminum alloy-temper.
The basic allowable tension strength (TA ) for a UNC fastener, where A r is the tensile stress area, is given by the lesser of the
following two equations:
(10.4)
(10.5)
For a spaced-thread fastener, where AR is the root area, the basic allowable tension strength (TA ) is given by the lesser of the
following two equations:
(10.6)
(10.7)
(JO.JO)
(10.J J)
For aluminum components (for a variety of aluminum alloy-tempers) with tapped holes, the equations for allowable pull-out,
based on internal threads only, are given in Section 22.0. These equations are mathematically equivalent (within rounding
accuracy) to the pull-out equations in the specification in the Aluminum Design Manual. There are three behavior regions,
based on thickness: thin (yield controls), thick (shear strength of internal threads governs) and a transition region between
these two.
Note that pull-out values, based on internal threads, are to be divided by k1 if this parameter exceeds 1.0 for the alloy-temper
being considered. Refer to the 20 IO ADM (Part 1: table A3.3 and Chapters D and F) for information on this notch-sensitivity
parameter. Correspondingly, if k1 exceeds 1.0, the minimum thickness (tM) values are to be multiplied by k,. Unless
otherwise noted, the tabulated values of pull-out and minimum thickness in this TIR are for alloy-tempers with k1 = 1.0.
The aluminum pull-out equations were solved for thickness t, in order to determine the minimum thickness (t = tM) of
aluminum needed to develop a UNC fastener's basic allowable tension (TA ). In the following equations, Fru and Fry are for
the alloy-temper used for the tapped aluminum component. The overall range of thickness considered is 0.060" S t S
0.375". See below for the specific thickness range for a particular equation, and for definitions of the quantities C1 and C2 ,
and P1 through PN . The equations are:
(JO.J2)
(10.J3)
(10.J4)
(JO.J5)
The quantities C1 and C2 , and P1 through PN , are given below:
Similarly, the pull-out equations were solved to find the minimum thickness (t = tM ) of aluminum needed to develop a
spaced-thread fastener's basic allowable tension (TA ). For spaced-thread fasteners, the set of equations is considered to apply
in the thickness range from 0.038" to 0.375", inclusive. As noted, however, individual equations apply to smaller ranges of
thickness. See below for the quantities C3, PR and P5. See UNC equations for Ci , and P1 to Pl . The resulting equations are:
(10.16)
(10.17)
(10.18)
(10.19)
The quantities C3 , and PR and Ps , are given below. See UNC equations for Ci , and P1 to Pl .
The pull-out equations used for UNC-thread fasteners, installed in tapped holes in A36 steel, follow. Fru applies to the
tapped steel component. Note that the thin-region equation also applies to spaced-thread fasteners. For the transition and
thick regions for spaced-thread fasteners, n and Ars, are the same as the UNC fastener of the same diameter. For spaced
thread fasteners, the thin region is considered to begin at 0.038".
(10.20)
(10.21)
(10.22) PA = (t - 0.25)[3 n ATS/ Fru /(SF .,/3)] + (0.375 - t)[1.7 d Fru fSF]
The preceding equations were solved for thickness t, in order to detennine the minimum thickness (t tM) of steel needed to =
develop a UNC fastener's basic allowable tension (TA ). See below for definitions of PE and PF . For spaced thread fasteners, use
the fastener's basic allowable tension for TA , and use n and A rs, for the UNC fastener of the same diameter. Also, for spaced
thread fasteners, the thin region is considered to begin at 0.038". The resulting equations are:
(10.23)
(10.24)
(10.25)
where:
The minimum thickness (tM ), required to develop a fastener's basic allowable tension strength TA , is given in the preceding
equations based on internal-thread strength. The minimum thickness is based on the greater of the thickness values based on
internal threads and external threads. The length of thread engagement must also equal or exceed tM in order to develop the
basic allowable tension TA . Determination of tM is based on solving the pull-out equations for a required thickness (t = tM)
for a given value of allowable tension (PA = TA ) for the screw. For fasteners with UNC and spaced threads installed in a
particular tapped material, the table values of tM were determined by comparing the basic TA for each fastener with the
maximum value of PA for the thin region (denoted by Pe for steel) and the minimum value for the thick region (denoted by PF
for steel). The equation for the appropriate region was then used to calculate the required tM value. A similar approach was
used for tapped aluminum.
Tables 20.1 to 20.13 also list the allowable pull-out values for screws installed in tapped 3/8" thick components, both steel
(A36) and aluminum (6063-TS and 6063-T6). Full engagement of the screw and tapped threads is presumed. For these
tables, three strength items were considered and the least of the three was listed in the table as the allowable value: basic
allowable tension strength of fastener, pull-out allowable based on internal-thread strength, and pull-out allowable based on
external-thread strength.
In addition, Tables 22.1 to 22.12 in Section 22.0, for a variety of aluminum alloy-tempers, present allowable pull-out values
for a range of fastener diameters (UNC and spaced thread) installed in aluminum ofvarious thicknesses. The tables in Section
22.0 are based only on internal-thread strength. In using the tables in Section 22.0, the designer must also consider the
fastener's basic allowable tension strength and its external-thread strength.
There is a limit to the benefit ofincreasing the length ofengagement. In many but not all cases, little, ifany, added allowable
strength is gained by exceeding a length equal to twice the nominal thread diameter. For spaced threads, the effective length
of fasteners with tapered points begins at the point of full diameter threads.
11.0 PULL-OVER OF SCREW HEAD IN CONTACT WITH ALUMINUM AND
COLD-FORMED STEEL
For the case of the screw head in contact with aluminum, per the Aluminum Association's ADM 2010 (Section J.5), there are
three equations to determine allowable pull-over force (PovA ): one for non-countersunk screws, one for non-countersunk
screws with all-metal washers and another for countersunk screws with an 82° nominal head angle.
Non-countersunk screws (* ):
(J 1.1)
Non-countersunk screws with all-metal washers (integral or non-integral with head; t1 ;::: 0.040"; if t1 I Dws > 0.5, use t1 I
Dws = 0.5; see** for hole sizes):
(11.2)
Countersunk screws (0.060" ::: t1 < 0.190"; if t1 Id> 1.1, use t1 Id= 1.1):
(11.3) PovA = (0.27 + 1 .45 t1 /d)d t1 FrnfSF
where:
Cpov = 1.0 for valley fastening and 0.7 for crown fastening, for corrugated roofing and siding; equals 1.0 for
two joined components in contact at the screw
t1 = nominal thickness of the part in contact with the screw head or washer
Fr ui = tensile ultimate stress of part in contact with head or washer
Frn = tensile yield strength of the part in contact with head or washer
Dws = larger of the nominal washer diameter and the screw head diameter, but no greater than 5/8 in.
(16mm). The washer may be integral to tlhe screw head.
Dn = nominal diameter of the hole in the material under the screw head
d = nominal diameter of screw
SF = safety factor ( SF equals 3.0 ford $ 1/4"; SF equals 2.5 ford 2: 5/16")
For * (Eq. 11.1), the allowable pull-over for non-countersunk screws need not be less than the value based on Eq. 11.3 for
countersunk screws. The holes may be as much as 0.062" oversize (i.e., hole diameter$ d + 1/16").
For** (Eq. 11.2), the following nominal hole sizes (average of0.013" oversize) apply:
Screw size d = screw diam. {nom.} Du. = hole size {nom.} Drill bit size
#8 0.164" 0.177" 16
#10 0.190" 0.201" 7
#12 0.216" 0.228" 1
1/4 0.250" 0.266" H
TABLE 11.1
For the case of the screw head in contact with a cold-formed steel member (t $ 3/16"), per the AISI specification (Section
E4), the allowable pull-over force is given by:
(11.4) PovA = 1.5 t1 D'w FTu /Sp
where:
t1 = thickness of connected member in contact with screw head or washer
FTu = tensile ultimate stress of steel member in contact with head or washer
Sp = safety factor (SF equals 3.0 for d $ 1/4"; SF equals 2.5 ford?. 5/16")
Dno = [see definition ofD'w 'J: diameter of round head or integral washer (hex washer-head); width across
diametrically-opposite points of a hex head (no integral washer)
D'w = effective pull-over diameter based on item (1) or (2) below, as applicable:
l ) for no independent washer used beneath a round head, hex washer-head, or hex head:
D'w = Dno $ 0.5''
2) for independent (non-integral; solid) steel washer beneath a round head, hex washer-head, or hex
head:
D'w = Dno + 2 tw + t 1 $ Dw
where:
tw = thickness of steel washer (0.050" minimum for t1 > 0.027")
Dw diameter of steel washer
==
For requirements for domed (non-solid) washers, refer to the AISI s.pecification.
For a bolt or screw head in contact with a steel member (t > 3/16"), there are no specific design rnles for pull-over in the
AISC specification (20 IO or 2005 editions).
In Supplement #2 (issued 2010; Section E4.5.l) to the cold-formed steel specification, there is an interaction equation for
combined shear and pull-over. This applies to certain screw diameters (#12 and #14 screws) and to a particular thickness
range (0.0285" $ t1 $ 0.0445" ). Also, it applies to t2 / t1 ?. 2.5 , where t1 is the sheet in contact with the head,
Fu1 $ 70 ksi, and Dw $ 0.75". Here, Dw is the larger of the head or washer diameter. The supplement's equation has
been written in an equivalent ASD format using allowable shear and pull-over:
(11.5)
where:
V = required shear force (not factored)
T = required tension force (not factored)
PAs = allowable shear strength = 0.9 t1 d Fu 1 = 2.7 t1 d Fu 1 /3.0 = allowable bearing
PAPOV = allowable pull-over strength = 0.5 t1 Dw Fu1 = 1.5 t1 d w Fu1 /3.0
In addition, V $ PASH and T $ PA T must also be satisfied. Here, PAsH is the lesser of the screw's basic allowable shear strength
and its allowable bearing strength on each of components I and 2 ( t1 and t2 ). PA T is the least of three allowable values:
basic tension strength of the screw, pull-out and pull-over. For eccentrically-loaded connections that produce a non-uniform
pull-over force on the screw, a reduced allowable pull-over value (equal to 50% of the normal allowable value) is to be used
in the above equation.
Note that Eq. 11.5 applies only to particular screw diameters used to connect components in a limited thickness range. The
basic interaction equation (see Section 7.0) must also be considered. The basic interaction equation is a function of the
square of two ratios (tension to basic allowable tension, and shear to basic allowable shear) and pertains to all screws and
bolts.
Figure J.5.1
-H
,,(�
-� o � (V, /2.34), max. LJ
J ]
1
1 1
-- -
.-,�.
��
1 f
! -.. �- .
.
screw chase
I
i.--J
I ;::; .
,·
r ... ..
!=---
-:
L
7
-H
FIGURE 13.1
EQUATION 13.l:
V� = ��-='-���-:-;==================--=-
(24)(R - r)] 2 + (8.SP) 2
(Zrrr.m ) + (P. f) [ [
[(2 )(R - r)] 4
Ultimate lateral frictional resistance to sliding of a screw in a screw chase parallel to walls (length) of chase,
Tm
(lb.)
Vst
H/8
H
H
Cl.
CL
R = 0.125 in
r = 0.0944 in
Tm= 0.110 in
P= 0.05 in
T= 50 lb-in
/= 0.47
=
2nrm 2n(0.110) 0.691=
21lTm f = (0.691(0.47)) = 0.325
Pf= (0.05) (0.47) = 0.0235
24 (R- r) = 24 (0.125 -0.0944) = 0.734
2
(24 (R- r)J = (0.734) 2 = 0.539
2
(8 P) = ((8.5) (0.05)) 2 = 0.181
.5
(0.53 co.1s1)
(0.325)( i�o) { co.o5) + (0.325)[ �\;4 }
o.
Vst = ------�----::-;========::--�
(O.S3 (0.l8l)
(0.691) - (0.0235) · [ �\; 4
(147. 7)(0.4257)
Vst =
(0.664)
94.693 lbs
Allowable = = 40.47 lbs
2.34
14.0 SCREW ENGAGEMENT IN SCREW CHASE
NOTE 1: Reference Figure 13. J for example ofa screw in screw chase when addressing Section 14.0
b b
EQUATION 14.1
R 8
(rr (1:0) - sin a)
A = R 2 ...:....-:.::;,=;,a....--:,.,--
=- _..:..
2 - 2
rr(R
e Ath r )
rr
( [�io
9 1)- sin[81.9]
Re =R 2
rr(R 2 - r 2 )
_ 1.4 29 - 0.990
- (O.l25) 2 ( r[ 1 )
r (0. 25) 2 - (0.0944) 2 )
0.4 39
= 0.0156 ( 0.0211 ) = 0.325
or 32.5% thread engagement, per thread
15.0 FASTENER SPECIFICATION CHECK LIST
A MECHANICAL PROPERTIES
B. FINISH
I. Clear or Natural
2. Colored
a. Painted
b. Burned
3. Other
C. CORROSION PROTECTION
l. As Fabricated
2. Plated
(Refer to appropriate ASTM Standards)
a. Zinc
b. Cadmium
c. Nickel
d. Chromium
3. Black Oxide
4. Waxed
5. Other
D. Fastener Exposure
Obviously, it is economically impractical for a fastener manufacturer or supplier to make available in stock all of the fastener
types and sizes in all of the different alloys with all of the different protective coatings available. As pointed out in the
"Protection Against Corrosion" section of this report, many types of stainless steel fasteners are readily available only in
alloys having lower resistance to corrosion than Type 316. SAE Grade 2 and Grade 5 carbon steel fasteners, while generally
available in 6 mm (1/4 in) diameter and larger sizes, may not be readily available in screws less than 6 mm (1/4 in) diameter.
On the other hand, structurally equivalent fasteners for the smaller screws made from commercial grades of steel wire are
readily available. Such items as the type of threads, heads, points and lot size will further influence availability.
Commonly used fasteners are generally available from stock and can be reasonably purchased in small quantity orders.
Fasteners are also available on a custom order basis but will usually require a large quantity of fasteners if a reasonable price
is to be obtained. Often the cost of fasteners in small quantity, custom orders could be so great as to economically rule out
their use.
The designer of curtain wall (fenestration) systems must recognize these limitations in availability and make acceptable
compromises in the selection of fasteners which will assure structural adequacy, effective resistance lo corrosive actions,
satisfactory over-all performance, and a cost which will not adversely affect the economic viability of the wall system.
17.0 SAMPLE CALCULATIONS FOR LOAD TABLES
Stainless-Steel Fastener: Alloy Groups 1, 2 and 3; Condition A; 1/4-20 Screw
Minimum Ultimate Tensile Strength Fu = 75,000 psi Fu! 3.0 = 2s,ooo psi
Minimum TeDsile Yield Strength Fy = 30,000 psi 0.75 Fy = 22,500 psi
TABLE 17.1
0.75 Fyis the smaller allowable tensile stress, and thus is used to ca lculate allowable loads in Load Table 10.
Also, yield controls because: FrdFru = 30,000/75,000 = 0.40 < 0.444 = 1/(3.0(0.75)) = 1/(0.75 S p)
2
A(S) = Ar= Tensile Stress Area = (1t/4)(D - (0.9743/N))
2
= (1t/4)(0. 2 5- (0.9743/ 20))
= 0.0318 2 in 2 ; rounds to 0. 0318 in 2
2
A(R) =A R=Thread Root Area = (1t/4)(D - (1. 2 263/N))
2
= (1t/4)(0. 2 5 - (1. 2 263/20))
= 0.0 2 795 in2 ; rounds to 0. 0 2 80 in 2 O
Allowable Bearing for A36 Steel = 0.9 Fu D t; for I= 1/8" and Fu = 58,000 psi
= 0.9(58,000)(0. 2 5)(0.1 2 5)
= 1,631 lbs
Allowable Bearing for 6063-TS Aluminum = (2/Q)Fru D t; fort = 1/8" and Fru = 22,000 psi
= ( 2 / 3.0) (2 2 ,000) (0. 2 5) (0.1 2 5)
= 458 lbs
Allowable Bearing for 6063-T6 Aluminum = (2/0.)Fru D t; forI - 1/8" and Fru - 30,000 psi
= ( 2 / 3.0) (30,000) (0. 2 5) (0.1 2 5)
= 625 lbs
_ TA sF../3
tM -(
I )-(
715.95(3.o)../3 / .
-0 134 .
/ (N A rsE Fru ) I
((20)(0.01851)(75,000)))- · m
Find minimum thickness (tM ) of tapped material, based on internal threads, to develop the basic allowable tension of
fastener. See also Figures 17.1, 17.2, 17.3.
6063-T5 aluminum:
PN = 0.25N Ars,Fru f(SF../3) ; lower limit for "thick" region
PN =0.25(20)(0.02723)(20,000)/(3.0../3) =576 lbs< 716 lbs
tM = TA SF ../3/(N ArssFru) = 715.95(3.0) (../3)/(20(0.02723)(22,000)) = 0.3105 in
Since 0.3105 in > 0.1489 in for external threads, internal thread strength governs.
6063-T6 aluminum:
PN = 0.25N Ars,Fru l(SF ../3); lower limit for "thick" region
PN = 0.25(20)(0.02723)(30,000)/(3.0../3) = 7'86 lbs> 716 lbs; thus check next limit
PM = 0.6651t D(0.125)FTv/(Sp ../3) = 0.665 1t (0.25)(0.125)(25,000)/((3.0)../3)
PM = 314 lbs < 716 lbs ; thus use transition equation
tM = (TA -0.25 C1 + 0.125C2)/CC2 -C1 )
Find allowable tension (least of allowable tension values based on tensile area [TA ], internal thread and external thread) for
tapped 3/8 in plates:
6063-T6 aluminum:
PA = t N ATS! FTu / (Sp ,/3) = 0.375 (20) (0.02723) (30,000) / 3.0
= 1,179 lbs; based on internal thread
PA = 1,179 lbs > 716 lbs,wh ci h s i the fastener'sbasic allowable tension (TA )
Since 0.375 in > 0.1489 in for external threads to develop TA , the plate can develop TA.
Thus maximum allowable tension equals 716 lbs.
*NOTE 3: For 6063-T5 aluminum , of thickness less than or equal to 0.500" (12.50 mm), the tensile ultimate strength is
22,000 psi (150 MPa) and the tensile yieldis 16,000 psi (110 MPa). For thicknesses from 0.501" (12.51 mm) to
1.000" (25.00mm), use 21,000 psi (145 MPa)for tensile ultimate and 13,000 psi ( (105 MPa)for tensile yield.
For all thicknesses of 6063-T6 aluminum, the tensile ultimate strength is 30,000 psi (205 MPa) and the tensile
yield is 25,000 psi (170 MPa). SJ values, in parentheses, are per the Aluminum Specification (2010 ed.).
Allowable Tension vs. Thickness; A36 steel, 1/4-20 (st. stl.; cond. A)
(Reference Table 20. 7)
3,200
,,
I I II I
I
I I I
I
,,
!
I "r
I I '.�'('
2,800
I
A31 steel ,.P"
' l...ol
I
1
rt
I I P' I
2,400
I
I
I I I
I
0!375 1...11
V
I
- I•
.·:.l Ii . .i...,,
vi
"Cl
I
I .•
,
/
.<.
. .,,,
_,
C 2,000
-
:I I
I .. T�
..
C ....
...
,r r:. - • Exterior thrd
, •.
0 I- -interior thrd
.iii 1,600 I .·1
C I
...·
,,•'
.............. int
l'J
..··
..·· .•
. ..·
!,,.
..
-
i
�-- q - � basic allow
,,"� I
......
I 'P
_g 1,200 I -min thick
< I I )·· 1
A v- ,,,
.. -- 0 25"
,,•' I
i I
· · , K-�
-i--
800
I . I
..
t
H:,,� - �- .
--
/
�
I
:;'I'
I
!
I I
I
I
. ·f
I I 0,1141'. I I
0
I I
�
I
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
Thickness (inches)
FIGURE 17.1
.n
�
- • Exterior thrd
2,000 I -interior thrd
I I
I
I 1...-
,
. .v
I
.............. int
I
l I
I . .,.;,
- � basic allow
� -min thick
_.,_
ii;"
lI I •1,
"O
I
.
C
g 1,500
� I I/ --+--
.
-
C ',
0 I�
'iii
.,
C
. ·'"' --....
I II
.,
l..o
3 1,000 I �
1,..' I I
,...,..
-�--... - - - - -
II""' �
1_...
....._,_,,,
I-
.- - - - ._. - - - - - -
�
6063-TS a ni ,um
UI
- -- -- .�
- l..ol�
� 16 i-- I I
,....
_l,,,I I
I
I
I ...•J.111i.-- I !
500
, I ! --· �
I
.......�-
...,..
0 �� I
-
I
II
. I
.... - - �---
�
. I
I
...... '
0 Q8 .... .... ····· L.,i....
•'
'
I
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
Thickness (inches)
FIGURE 17.2
-- ffiHE, . �
Ltcl--
fl 11111 jl I I lpj,'1 I
11. I ; I
:, 1 500 u I I I I
I I r,_I I
·;:;;
!,
C
,.,
I.A'
FH-H-11-Ll
C - · Exterior thrd
n. 1 111 1�1·
rr.�11
!JO
'
,_M
·
1 1 1
l,
OOO � "1 1
4
11 I - � basic allow
-I--
I-
0
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
Thickness (inches)
FIGURE 17. .3
1
Bolls,
Sc,ews, 1/4 thru
1-1/2
33.000-"l 60,000 36.000 60,000
•'·
18 35 - B70 8100 None
Studs \
1/4 thru
Bo�s. 314>1) 55,00()('i 74,000 57,000 74,000 18 35 - B80 B100 Ncne
2 Screws,
Sh.Ids OvOf 314
thru 1-112
33,000 60,000 36,000 60,000 18 35 - B70 8100 Nor.e
4 Sh.Jds
1/4 lhni
65,000 115,000 100,000 115,000 10 35 - C22 C32 Nooe
,,,,
1-1/2
Bolts, 1(,l thru 1 85,000 120,000 92,000 120,000 14 35 54 C2S C34
Screws, OVer1
5
stu:ts thru 1-112 74,000 105,000 81,000 105.000 14 35 50 C19 C30 I
5.1!'1 SEMS
No.4tl'uv
5/8
85,000 120,000 . . . - 59.5 C25 C40 -- I
5.i
Bolls,
S<:,Q,\y$
1/4 lhl\l 1 85,000 120,000 92.000 120,000 14 35 5o C26 C36 ,....,I ,,, .
,
Bolts, ,•....1 ......
1/4 th!V
8 Screws, 120.000 150,000 130,000 150,000 12 35 58.6 C33 C39
1-11?.
Stvds ...... ......
1/4 trru
8.1 SIUC!!I 120,000 150,000 130,000 160,000 10 35 SU C33 C39 None
-'-"/-
1-1/2
Bolls,
8.2 1/4 lhru 1 120,000 150,000 130.000 150,000 10 35 58.6 C33 C39
SCr0\'1$
Reprinted, with pennission, from SAE 1429-2011, Mechanical and Material Requirements for Externally Threaded Fasteners, copyright SAE
International, 400 Ccmmonwealth Drive, Warrendale, PA 15096. A copy of the complete standard may be obtainedfrom SAE Intemationa/,
www.sae.org.
(303,304, CW1 F593C •,4 lo%, incl 100 to 150 65 895 lo C32 95 60 20
XM1,
1B-8LW,
SH2 � :V.lol,inct 110 lo 150 75 C20 lo C32 105 70 15
302HO,
30358)
SH3 � 1 'A, lo 1'.4, ilCI 100 10 140 60 895 loC30 95 55 20
45 B90 lo C28 90 40 28
SH4 fiilQ 1� lo 1'h. incl 95 lo180
(316,
316l)
] SH1
SH2
F593E
F593F
•,4 lo%, incl
:V.lo1,inel
120 lo160
1101o150
95
75
C24 lo C36
C20 lo C32
115
105
90
70
12
15
20 40
AF F593J Y, 1o 1v...1rc1 65 lo 85 20 885 max 60
30
A F5931< Y, lo 1 V..,Incl 75 lo 100 30 865 lo 95 70 30
60 20
CW1 F59SI.. y, lo%,incl 100 to 150 65 895 lo C32 95
3
CW2 F593M 'Y, lo1 v... lrcl 85 lo 140 45 880 lo C32 80 40 25
(321,347) 115 90 12
SH1 fill:! V, lo�.Incl 120 lo 160 95 C24 lo C36
15
SH2 F593K :V.lo1,incl 110lo 150 75 C20 lo C32 105 70
20
SH3 � 1',f,lo1•.4,ilCI 100 lo 140 60 895 loC30 95 55
SH4 ,� 1o 1v
... incl 95 lo 130 45 890 loC28 90 40 28
�9;!d
Fe-lllicAI s
4 AF F593X v, lo 1 'h. 1rc1 55 lo 75 30 885 max 50 25
(430,430F) A F593N Y, loI •h,lrcl 55 lo 75 30 885 max 50 25
Reprinted, with pennission.from dSIM.EJ.21-LJ.a S.€f!.tJfli!rd.S!JJ:.,i{katiQ!J. [Q.t:. S./JiJ./.JJ.lw :lJ.'1:.l/Jg.fts., lf.g_Q1R�CW!t go{!_S.tud� copyright ASTM lntemational, JOO
Bair Harbor Drili'I!, West C-Onshohocken, PA /9428. A copy ofthe complete standard may be obtainedfrom ASTM lntemational, www.rutm Qrg.
l'bmal lSA(E) TSA(O External Threads - Cass 2A htemal Threads -Cass 28 Tapots
Thread 0� A(S) Sa. h/Thread Mlioc Clarreter Alch Clarreter Iffier Clarreter Rich llan'eter KBasi: Comrerciat Dis
llarreter & Thread Tensile A(R) Iffier
Thread Alf Clarreter Stress Area Thread fb)I llarreter Dec.
heh heh Sa. h. Area Sq. h. External hternal Mix. Mn. Mix. Mn. Mn. Mix. Mn. Mix. heh �./Size fquiv�t
f/6..32 0.1380 0.0091 0.0078 0.0060 0.0090 0.1370 0.1310 0.1170 0.1140 0.1040 0.1140 0.1180 0.1210 0.0997 36 0.1065
#a-32 0.1640 0.0140 0.0124 0.0070 0.0100 0.1630 0.1570 0.1430 0.1400 0.1300 0.1300 0.1440 0.1480 0.1257 29 0.1360
#10-24 0.1900 0.0175 0.0152 0.0110 0.0170 0.1890 0.1820 0.1620 0.1590 0.1450 0.1560 0.1630 0.1670 0.1389 25 0.1495
#12-24 0.2160 0.0242 0.0214 0.0130 0.0190 0.2150 0.2080 0.1880 0.1850 0.1710 0.1810 0.1890 0.1930 0.1649 16 o.mo
-
1/4-20 0.2500 0.0318 0.0280 0.0180 0.0270 0.2490 0.2410 0.2160 0.2130 0.1960 0.2070 0.2180 0.2220 0.1887 7 0.2010
5/16-18 0.3125 0.0524 0.0469 0.0260 0.0380 0.3110 0.3030 0.2750 0.2710 0.2520 0.2650 0.2760 0.2820 0.2443 F 0.2570
318-16 0.3750 0.0775 0.0699 0.0360 0.0520 0.3740 0.3640 0.3330 0.3290 0.3070 -0.3210 0.3340 0.3400 0.2983 5/16 0.3125
-
7/16-14 0.4375 0.1063 0.0961 . 0.0480 0.0700 0.4360 0.4260 0.3900 0.3850 0.3600 0.3760 0.3910 0.3970 0.3499 u 0.3680
1/2-13 0.5000 0.1419 0.1292 0.0600 0.0860 0.4990 0.4880 0.4490-- 0.4440 0.4170 0.4340 0.4500 0.4570 0.4056 27/64 0.4219
9/16-12 0.5625 0.1819 0.1664 0.0740 0.1060 0.5610 0.5500 0.5070 0.5020 0.4720 0.4900 0.5080 0.5150 0.4603 31/64 0.4844
518-11
3/4-10
-
0.6250 0.2260 0.2071
0.7500 -·0.3345 0.3091
0.0910 -0.1300
0.1210 0.1720
0.6230
0.7480
0.6110
0.7350
0.5640 0.5590-
0.6830 0.6770
0.5270 0.5460
0.6420 0.6630
0.5660
0.6850
0.5730
0.6930
-0.5135
0.6273
17/32
21/32
0.5312
0.6562
7/8·9 0.8750 0.4617 0.4286 0.1590 0.2250 0.8730 0.8590 0.8010 0.7950 0.7550 0.7780 0.8030 0.8110 0.7387 49164 0.7656
1-8 1.0000 0.6057 0.5630 0.2070 0.2920 0.9980 0.9830 0.9170 0.9100 0.8650 0.8900 0.9190 0.9280 0.8466 7/8 0.8750
Formulae Used in calculating Table Values Annlieable Material
A(�= n{D-(!).9743/N)f /4
-
- -�·
- -
UNC Fasteners /Ill Diameters --------
- -
-- -- -- -----
-
SAE Grade 2 (s 9116') For AR Diameters Bfective Area (UNC Threads) Effective Area (Spaced Ttveads)
Fu (Min. Ultimate Tensile Strength) 74,000 psi F-r=Fu/ SF A(R) =TT (D-1.2269/N\2 I 4 A(R) =nK'/4
Fr (Allow. Tensile Stress, °'114") 24,667 psi Allowable Tension= FrlA(S)) A(S) = TT (D-0.97431N\2 I 4 A(S)=nK2/4
Fr{Allow. Tensile Stress: O> 114') 29,600 psi Fv =Fu / ( SF x sq rt (3))
Fv (Allowable Shear Strass: 0$1141 14,241 psi Allowable Single Shear �F.{A(R))
Fv (Allowable Shear Strass: 0>114') 17,090 psi
NOTE4:
1. Values are taken from AJSC, ASTM, IF/, SAE and AA documents. K values/or spaced threads are taken as the minimum values in /Fl Fastener Handbook, 8th Ed.
2. Safety Factor used/or fasteners with diameters 1/4" or less is 3.0, Safety Factor usedfor fasteners with diameters 5/16" or greater is 2.5.
SAE Grade 5 (s 9/16") ASThl A449 (� 5/8") For Al Diameters Effective Area IUICThreadsl Etlacllwl Area (Spaced Threads)
Fu (Min. Ultimate Tensile Strength) 120,000 psi 120,000 psi F,. =F,/SF AIRl = n l[).1.22691N)2 14 A(Rl = nK1/4
Ft (Allow. Tensie Stress, OS1/4") 40,000 psi !'¥A Alowable Tension= Fr[A(S) l AISl - n /[).0,974�2 / 4 A/Sl =nK'/4
Fr (Allow. Tensie Stress, D>1/4") 48,000 psi 48,000 psi Fv= Fu/( SFx sa rt (3))
Fv(Allowable Shear Suass: �114') 23,094 psi NIA ,,_bleSingleShear •FyjA(R)]
FvfAllowable Shear Strass· 0>1/4"1 27713 OSI 27,713 osi
NOTES:
1. Values are takenfrom AJSC, ASTM. IF/, SAE and AA documents. K values for spaced threads are taken as the minimum values in IF/ Fastener Handbook, 6th Ed.
2. Safety Factor used for fasteners with diameters 1/4" or less is 3.0, Safety Factor used for fasteners with diameters 5/16" or greater is 2.5.
3. Fasteners with diameters of 5/8" or grea/er are fabricatedfrom carbon steel complying wilh ASTM A449 Type
NOTE6:
1. Values are taken from AISC, ASTM. lFl, SAE and AA documents. K values/or spaced threads are taken as the minimum values in lFl Fastener Handbook, 6th Ed.
2. Safety Factor used for fasteners with diameters 1/4" or less is 3.0 , Safety Factor used for fasteners with diameters 5/16" or greater is 2.5.
AAMA TIR-A9-14
���°.!,.,������������v��= eM�==��- by l.lldkM!Illl of Chjna Nay ID$!ofS!andanl@tion on Thu Mar 19 2015.11 may
Page 45
TABLE 20.5: Fastener Capacity
.
'• ASTM A 325 (UNC Threads) ·'
,.
[-,
2
Fu (Min. Ultimate Tensile Strength) 120,000 psi Fr = Fu/ SF
Fr (Allow. Tensile Stress, DS1/4")
I NIA Allowable Tension= Fr[A(S)J A(S) = TT (0.0.9743/N)2 / 4
i
Fr (Allow. Tensile Stress, D> 1/4") .48,000 psi Fv = Fu / ( SF x sq rt (3))
Fv (Allowable Shear Strass; Ds1/4") NIA Allow able Sinqle Shear =Fv[A(R)]
Fv /Allowable Shear Strass: 0>1/4"1 ., 27,713 osi
NOTE 7:
I. Values are taken from AJSC, ASTM. !FI, SAE and AA documents. K values for spaced threads are taken as the minimum values in IF/ Fastener Handbook, 6th Ed.
2. Safety Factor used/or fasteners with diameters 112" or greater is 2.5.
• •• • • • • • •• •
oer nch {in) {in2) {in2) {lbs) {lbs) {lbs) A36 6063-TS 6063-TS A36 6063-TS 6063-TS A36 6063-TS 6063-TS
1/2-13 0.5000 0.1419 0.1292 8,514 4,476 8,953 3,263 I > 3/8" 5,642
• • •
9116-12 0.5625 0.1819 0.1664 10,917 5,763 11,527 3,670 > 3/8" 6,444
I
• • • •
5/8-11 0.6250 0.2260 0.2071 13,560 7,173 14,346 4,078 > 3/8" 7,148
• • • •
3/4-10 0.7500 0.3345 0.3091 20,068 10,706 21,413 4,894 > 3/8" 8,612
I
• • • • •
7/8-9 0.8750 0.4617 0.4285 27,704 14,845 29,691 5,709 > 3/8" 10,158
1-8 1.0000 0.6057 0.5630 36,345 19,502 39,004 6,525 > 3/8" 11,696
NOTES:
I. Values are takenfrom AJSC, ASTM, IF/, SAE and AA documents. K values/or spaced threads are taken as the minimum values in IF/ Fastener Handbook, 6th Ed.
2. Safety Factor used/or fasteners with diameters 112" or greater is 2.5.
3. The Aluminum Design Manual stales A490 bolts shall not be used where it may contact aluminum.
Cond. A For Al Dameters Effective Area (UIICThreadsl Effecv,,e Area /Spaced Thtoads)
Fu (Min. Ullimate Tensile Strength) 75,000 psi F,- = 0.75 F. ACRI= TT 10-1.2269/N\2 / 4 AIR) =nK'/4
Fr(Allow. Tensile Stress, 0.1/4' ) 22,500 psi Allowable Tension= F,,IA(Sll A(S) = TT (D-0.9743/N\2 / 4 Al$) =nK'/4
Fr(Allow. Tensile Stress, O> 1/4') 22,500 psi Fv = 0.75 F./ (sa rt 13))
Fv(Allowable ShearSlrass: 0$.1/4') 12,990 psi =FvlA (R) l
FvlAllowable ShearStrass· 0>1/4') 12 990 osi
NOTE9:
1. Values are taken from AISC. ASTM, IF/, SAE and AA documents. K values for spaced threads are taken as the minimum values in IFl Fastener Handbook, 6th Ed.
2. Safety Factor used/or fasteners with diameters 1/4 11 or less is 3.0, Safety Factor used/or fasteners with diameters 5/16" or greater is 2.5.
3. For these groups and condition (A), Fy = 30,000 psi. Thus tensile and shear yields govern the allowable tension and shear values (i.e., 0. 75 Fy < F,/SF)
-' #6-32 0.1380 0.0091 0.Qlli_ 136 68 135 900 253 345 0.0879 0.1419 0.1167 136 136 136
- #8-32 0.1640
#10-24 0.1900
0.0140
0.0175
0.0124
0-:-0151
210
263
107
131
215
262
1,070
1,240
301
348
410
475
0.1072
0.1144
0.1703
0.1750
0.1269
0.1338
210
263
210
263
210
263
#12-24 0.2160 0.0242 0.0214 362 185 370 1,409 396 540 0.1325 0.1997 0.1537 362 362 362
1/4-20 0.2500 0.0318 0.0280 4n 242 484 1.631 458 625 0.1489 0.2170 0.1682 477 477 477
5116-18 0.3125 0.0524 0.0469 786 406 812 2,039 573 781 0.1940 0.2319 0.1940 786 786 786
! 318-16 0.3750 0.0775 0.0699 1,162 605 1,211 2,447 688 938 0.2319 0.2772 0.2319 1,162 1,162 1,162
0.1063 0.0961 1,595 833 1,665 2,855 802 1,094 0.2722 0.3193 0.2722 1,595 1,595 1,595
- 7/16-14 0.4375 0.1419 0.1292 2,128 1,119 2,238 3,263 917 1,250 0.3135 0.3730 0.3135 2,128 2,128 2,128
1/2-13 0.5000
9/16-12 0.5625 0.1819 0.1664 2,729 1,441 2,882 3,670 1,031 1,406 0.3511 > 318' 0.3511 2,729 2,444 2,729
518-11 0.6250 0.2260 0.2071 3,390 1,793 3,586 4,078 1,146 1,563 >318" >3/8' >3/8" 3,245 2,711 3,245
314-10 0.7500 0.3345 0.3091 5,017 2,677 5,353 4,894 1,375 1,875 >3/8' >3/8' >3/8" 3,929 3,266 3,929
7/8-9 0.8750 0.4617 0.4285 6,926 3,711 7,423 5,709 1,604 2,188 >318' >3/8' >3/8' 4,670 3,853 4,670
1-8 1.0000 0.6057 0.5630 9,086 4,875 9,751 6.525 1,833 2,500 >318' >318" >318' 5,379 4,437 5,379
Group 1,2,3-Cond. SH S S/8'0ia. i 3/4" Ila. ForAl llamoters EffectiveArea llJIJC Threads\ Effeclive /vea (Spaced Threads)
Fu (Min. UIUmale Temile Stronglh) 120,000 psi 110,000 psi Fr= F.JSF
2
A{Rl=n I0.1.2269'Nl / 4 AIR\=nX'/4
Ft (Alow. TensOe Stress, OS1W) 40,000 psi 36,667 psi Alowable Tension= F.IAISII A(S)=n (0.0.97431N) / 4
2
AIS) =nK'/4
Ft (Allow. Tensile Stress, D>1/41 48,000 psi 44,000 psi Fv =Fu/I SFx sq rt (3\l
Fv (Allowable Shear Strass; DS1/41 23,094 psi 21,170 psi -Ille SlnoM Shear •F,(A(R)l
Fv/Allowable Shear Strass· 0>1/4"\ 27 713 nsl 25 403 osi
NOTEJ2:
1. Values are taken from AISC, ASTM. lFL SAE and AA documents. K values for spaced threads are taken as the minimum values in IFJ Fastener Handbook, 6th Ed.
2. Safety Factor used forfasteners with diameters 1/4" or less is 3.0, Safety Factor used/orfasteners wilh diameters 5116" or greater is 2.5.
3. Fasleners with diameters o/3/4" and greater are fabricatedfrom different material thanfasleners less than 3/4" in diameter.
4. Rockwell hardness to be limited to C34 maximum.forfasteners in contact with aluminum.
,. . .
STAN.ES$ STEB..- Alloy Group 4, Condition A (UNC Treads) .. ;
Group 4-Cond. A For All Diameters Bfectille Area (UNC Threads\ Effeellve Area (Spaoed Threads)
Fu (Min. Ultimate Tensile Strength) 55,000 psi F, = F.JSF AIR\=TT 1().1.2269/N\2 / 4 AIR)=nK1/4
Fr (Allow. Tensile Stress. 0'1/4") 18,333 psi Allow able Tension= F.IAIS\1 AISl =TT /().0.9743/N\2 / 4 A($) =nK2/4
FT (Allow. Tensile Stress,0> 1/4") 22,000 psi Fv =Fu / ( SF x sq rt 1311
Fv (Allowable Shear Strass; D:s1/4") 10,585 psi Allowable Single Shear •FJAIR)I
Fv lAJlowable Sllear Strass; D>1/4 "l 12,702 DSi
NOTE 13:
1. Values are taken from AISC, ASTM. IFI, SAE and AA documents. K values/or spaced threads are taken as the minimum values in IFI Fastener Handbook, 6th Ed
2. Safety Factor used/or fasteners with diameters 1/4" or less is 3.0, Safety Factor used/or fasteners with diameters 5/16" or greater is 2.5.
Group 5-C.Ond. H For Al Clameters Bfective Area 11.N:: Threads) El!eclMt At.. (Spaced Threads)
Fu (Min. Ultimate Tensile Strength) 110,000 psi Fr-F,JSF A(R) =n (�1.226Q/IIJ\2 / 4 A(RJ =nK'/4
Ft (Allow. TensBe Stress, 0.1/4") 36,667 psi Alowable Tension= FrlA(S\l AIS)=n (�0.9743/N\2 / 4 A(S) =nK'/4
Fr(Allow. Tensfle Stress. D> 1/4-') 44,000 psi fv =Fu/ I SF x sa rt (3ll
Fv(Allowable Shear Strass; ()s114') 21,170 psi Alowlble Single Shur •f.,(A(R))
Fu/Allowable Shear Strass· 0>1/4') 25403 osl
NOTEJ4:
1. Values are taken from AlSC, ASTM. IF!, SAE and AA documents. K values for spaced threads are taken as the minimum values in !Fl Fastener Handbook, 6th Ed.
2. Safety Factor used/or fasteners with diameters 114" or less is 3.0, Safety Factor used forfasteners with diameters 5116" or greater is 2.5.
3. Minimum 16% Cr (chromium) content required.for fasteners in contact with aluminum.
Group 5-Cond Hf For Al Diarreters Bfective Area lu-K:Threads) Elfecl!ve Area (Spaced Thtoads)
Fu (Min. Ultimate Tensile Slrength) 160,000 psi Fr=Fu/ SF A(R) = TT (D-1.2269/Nl2 / 4 A(Rl =nK'/4
Fr (Allow. Tensile Stress, 0"1/4") 53,333 psi Alow able Tension = Fr!A(S)] A(S) = TT (D-0.9743/N12 / 4 A(Sl =nK'/4
Fr (Allow. Tenslle Stress, O>1/4") 64,000 psi Fv =Fu/( SF x SQ rt (3))
Fv (Allowable Shear Strass; �1/4') 30,792 psi Allowable Single Shear •F.(A(R)J
Fv /Allowable Shear Strass· 0>1/4 "1 36,950 osi
NOTE 15:
J. Values are taken from AISC, ASTM, IF!, SAE and AA documenls. K values for spaced threads are /aken as !he minimum values in IF/ Fastener Handbook, 6th Ed.
2. Safety Factor usedfor fasteners with diameters 1/4" or less is 3.0, Safety Factor used for fasteners with diameters 5116" or greater is 2.5.
3. Rockwell hardness to be limited to C34 maximum,Jorfasteners (see shaded columns above) in contact with aluminum. Most of the hardness values for this fastener ma/erial exceed C34.
·mimttt, ,L\8
mm\m'I B
mmm.·-� .... - [:1l D
j
·nmmrn
... ummmfit,I' 13c-
� BT
\ltmi1� ('
' I
,·1'1!
,,,\� \\\\11
.., D
WmIDE*rl Pr.�i
.,,I ,•\\11\_l,;w.;
•'t;&[_ lli r
t,�i!=
�\,I ,,\ .....,,
i;;
'-'I
-�
r··�·-1�
�\I�
,\\ . T
FIGURE: 21.1
TABLE 21.1
Aooroximate Pierced or Extruded Hole Sizes for Types AB, B and BP Steel Thread Forminf! Screws*
Pierced or
Screw Metal Pierced or Extruded Screw Metal
Extruded Hole
Size Thickness Hole Required Size Thickness
Reauired
In Steel, Stainless Steel Monet Metal and Brass Sheet Metal In Aluminum Allov Sheet Metal
0.015 0.111 0.024 0.111
0.018 0.111 0.030 0.111
6 0.024 0.111 6 0.036 0.111
0.030 0.111 0.048 0.111
0.036 0.111
O.ot8 0.120 0.024 0.120
0.024 0.120 0.030 0.120
7 0.030 0.120 7 0.036 0.120
0.036 0.120 0.048 0.120
0.048 0.120
0.018 0.136 0.024 0.136
0.024 0.136 0.030 0.136
8 0.030 0.136 8 0.036 0.136
0.036 0.136 0.048 0.136
0.048 0.136
0.018 0.157 0.024 0.157
0.024 0.157 0.030 0.157
10 0.030 0.157 10 0.036 0.157
0.036 0.157 0.048 0.157
0.048 0.157
0.024 0.185
0.030 0.185
12 0.036 0.185
0.048 0.185
0.030 0.209
l/4 0.036 0.209
0.048 0.209
Annronriate Drilled Hole Sizes for Tvnes AB. B and BP Steel Thread Forminl! Screws*
Screw
Size I Hole
Required
Drill Size
Minimum Material
Thickness
Penetration In Blind Holes
Min.
In Plywood (Resign Impregnated)
Max.
NOTE 17: All dimensions are given in inches except whole number screw and drill sizes.
*Since conditions differ widely, it may be necessary to vary the hole size to suit a particular application.
fData applies to Types B and BP only.
TABLE 21.S
Approximate Drilled or Clean Punched Hole Sizes for Ty!Pes AB, B and BP Steel Thread Forming Screws*
Screw Metal Hole Screw Hole
Drill Size Metal Thickness Drill Size
Size Thickness Required Size Required
In Steel, Stainless Steel, Monet Metal and Brass Sheet Metal In Aluminum Alloy Sheet Metal
0.015 0.104 37 0.030 0.104 37
0.018 0.104 37 0.036 0.104 37
0.024 0.106 36 0.048 0.104 37
0.030 0.106 36 0.060 0.106 36
6 0.036 0.110 35 6 O.Q75 0.110 35
0.048 0.111 34 0.105 0.111 34
0.060 0.116 32 0.128 to 0.250 0.120 31
O.Q7S 0.120 31
0.105 0.128 30
O.Ql 8 0.116 32 0.030 0.113 33
0.024 0.116 32 0.036 0.113 33
0.030 0.116 32 0.048 0.116 32
0.036 0.116 32 0.060 0.120 31
7 7
0.048 0.120 31 O.Q75 0.128 30
0.060 0.128 30 0.105 0.136 29
O.Q7S 0.136 29 0.128 to 0.250 0.136 29
0.105 0.140 28
0.024 0.125 1/8 0.030 0.116 32
0.030 0.125 1/8 0.036 0.120 31
0.036 0.125 1/8 I 0.048 0.128 30
0.048 0.128 30 0.060 0.136 29
8 0.060 0.136 29 8 O.Q75 0.140 28
O.Q75 0.140 28 0.105 0.147 26
0.105 0.149 25 0.125 0.147 26
0.125 0.149 25 0.135 0.149 25
0.135 0.152 24 0.162 to 0.375 0.152 24
0.024 0.144 27 0.036 0.144 27
0.030 0.144 27 0.048 0.144 27
0.036 0.147 26 0.060 0.144 27
0.048 0.152 24 0.075 0.147 26
0.060 0.152 24 0.105 0.147 26
10 10
O.Q75 0.157 22 0.125 0.154 23
0.105 0.161 20 0.135 0.154 23
0.125 0.169 18 0.164 0.159 21
0.135 0.169 18 0.200 to 0.375 0.166 19
0.164 0.173 17
0.048 0.161 20
0.024 0.166 19 0.060 0.166 19
0.030 0.166 19 O.Q75 0.173 17
0.036 0.166 19 0.105 0.180 IS
0.048 0.169 18 0.125 0.182 14
0.060 0.177 16 0.135 0.182 14
12 12
0.075 0.182 14 0.164 0.189 12
0.105 0.185 13 0.200 to 0.375 0.196 9
0.125 0.196 9
0.135 0.196 9
0.164 0.201 7
0.060 0.199 8
0.030 0.194 10 0.o75 0.201 7
0.036 0.194 10 0.105 0.204 6
0.048 0.194 10 0.125 0.209 4
0.060 0.199 8 0.135 0.209 4
0.o75 0.204 6 0.164 0.213 3
1/4
1/4 0.105 0.209 4 0.187 0.213 3
0.125 0.228 I 0.194 0.221 2
0.135 0.228 I 0.200 to 0.375 0.228 I
0.164 0.234 15/64
0.187 0.234 15/64
0.194 0.234 15/64
NOTE 18: All dimensions are given in inches except whole number screw and drill sizes.
*Since conditions differ widely, it may be necessary to vary the hole size to suit a particular application.
Hole sizes for metal thicknesses above .075 inch are for Types Band BP only.
Approximate Hole Sizes for Types D, F, C and T Steel Thread Cutting Screws*
Stock Thickness
Screw
Size 0.050 0.060 0.083 0.125 0.140 3/16 1/4 5/16 3/8 1/2
Hole Sizes in Steel
6-32 .1100 .1130 .1160 .1160 .1200 .1250 .1250
8-32 .1360 .1405 .1405 .1440 .1470 .1495 .1495 0.1495
10-24 .1520 .1540 .1610 .1660 .1695 .1730 .1730 0.1730 .1730
10-32 0.1590 .1660 .1660 .1695 .1695 .1770 .1770 0.1770 .1770
12-24 .1800 .1820 .1910 0.1910 .1990 .1990 0.1990 .1990 .1990
1/4-20 .2130 .2210 0.2210 .2280 .2280 0.2280 .2280 .2280
1/4-28 .2210 .2280 0.2340 .2344 .2344 0.2344 .2344 .2344
5/16-18 .2770 0.2813 .2900 .2900 0.2900 .2900 .2900
5/16-24 .2900 0.2900 .2950 .2950 0.2950 .2950 .2950
3/8-16 .3390 0.3390 .3480 .3580 0.3580 .3580 .3580
3/8-24 .3480 0.3480 .3580 .3580 0.3580 .3580 .3580
Hole Sizes in Aluminum
6-32 .1094 .1094 .1110 .1160 0.11,60 .1200 .1250
8-32 .1360 .1360 .1360 .1405 0.1440 .1470 .1495 0.1495
10-24 .1495 .1520 .1540 .1590 0.1610 .1660 .1719 0.1730 .1730
10-32 .1610 .1610 .1610 .1660 0.1660 .1719 .1770 0.1770 .1770
12-24 .1770 .1800 .1850 0.1875 .1910 .1990 0.1990 .1990 .1990
1/4-20 .2055 .2130 0.2130 .2210 .2280 0.2280 .2280 .2280
1/4-28 .2188 .2210 .2210 .2280 .2344 0.2344 .2344 .2344
5/16-18 .2720 .2720 .2810 .2900 0.2900 .2900 .2900
5/16-24 .2812 0.2812 .2900 .2950 0.2950 .2950 .2950
3/8-16 .3281 0.3320 .3390 .3480 0.3480 .3480 .3480
3/8-24 .3438 0.3438 .3480 .3580 0.3580 .3580 .3580
Hole Sizes
6-32 0.1160 .1200 .1200 .1200
8-32 .1440 .1440 .1440 .1440
10-24 .1610 .1660 .1660 .1660
10-32 .1695 .1695 .1719 .1719
12-24 .1800 .1910 .1910 .1990
1/4-20 .2188 .2188 .2280
1/4-28 .2280 .2280 .2344
5/16-18 .2770 .2900
5/16-24 .2900 .2950
3/8-16 .3480
3/8-24 .3580
TABLE 21.7
Approximate Hole Sizes for Types BF and BT Steel Thread Cutting Screws*
Screw Size
Stock 12-14 1/4-14 5/16-12 3/8-12
6-20 8-18 10-16
Thickness
Hole Sizes* in Zin, c and Aluminum Die Castine:s
0.060 --- --- --- --- --- --- ---
0.083 --- --- --- --- --- --- ---
0.109 --- --- --- --- --- --- ---
0.125 0.1200 0.1490 0.1660 0.1910 0.2210 0.2810 0.344
0.140 0.1200 0.1490 0.1660 0.1910 0.2210 0.2810 0.344
3/16 0.1200 0.1490 0.1660 0.1910 0.2210 0.2810 0.344
1/4 0.1250 0.1520 0.1695 0.1960 0.2280 0.2810 0.344
5/16 0.1250 0.1520 0.1719 0.1960 0.2280 0.2900 0.348
3/8 --- --- 0.1719 0.1960 0.2280 0.2900 0.348
NOTE 19: All dimensions are given in inches except whole number screw and drill sizes.
•Since conditions differ widely, it may be necessary to va,y /he hole size lo suit a particular applicalion.
Hole sizes/or metal lhicknesses above 0.075 inch are/or Types Band BP only.
fHole sizes listed are slandard drill sizes.
Pull-out research (testing and analysis), which was conducted in the 1990s by several AAMA member companies, forn1ed the
basis for the pull-out equations in this TIR and in the Specification for Aluminum Structures. The results of this research
("Pull-out Capacities of Screws from Aluminum") were presented at the Aluminum Association's 2"d International Workshop
at Cornell University in October 1999.
PREDICTED PULL-OUT
Most of the actual (as opposed to allowable) pull-out values, from available testing, can be characterized by two types of
equations for the nominal pull-out strength (PN or ): one based on tensile yield strength Frr (to account for the stretching and
bending of the hole's circumference in "thin" aluminum) and one based on tensile ultimate strength Fru (to account for
shearing of internal threads in "thick" aluminum).
The test data, for tapped-aluminum thicknesses (t) of 1/8", 3/16" and 1/4", indicate a transition in pull-out behavior from
yielding (of thin aluminum) to shearing of the internal threads (thread stripping, in thick aluminum).
For spaced-thread fasteners, it is helpful to also consider the number of threads engaged (t n) in order to separate the three
behavior regions: thin (yield), thick (thread stripping), and transition.
Some alloy-tempers are notch sensitive (k1 exceeds 1.0). Refer to the 2010 ADM (Part 1: table A.3.3 and Chapters D and F).
For these cases, the nominal strength (P NoT), based on internal-thread strength, is to be divided by k. to determine a reduced
value, which is then divided by the appropriate safety factor (Sf).
Equations for nominal pull-out strength (no safety factor included) consist of equations 22.1 to 22.6. Each equation applies
to a behavior zone. Behavior zones for UNC (a, b, c) and spaced-thread (d, e, f) fasteners, are identified as follows:
UNC threads:
a) 0.060" ::;; t ::;; 0.125" (thin; yield)
b) 0.250" ::;; t ::;; 0.375" (thick; thread stripping)
c) 0.125" ::;; t ::;; 0.25" (transition)
Spaced threads:
d) 0.038" ::;; t :5 2 /n (thin; yield)
e) 4/n :5 t ::5 0.375" (thick; thread stripping)
f) 2/n :5 t :54/n (transition)
For representative plots, refer to Fig. 22.1(UNC, Unified National Coarse threads) and Fig. 22.2 (spaced threads).
The following equations are applicable for screws (nominal diameter d), in tapped holes, where 0.164" ::;; d ::5 0.5'' for
UNC threads and 0.164" :5 d ::5 0.375" for spaced threads.
I) The equations for UNC threads (screw-point types C, D, F, G and T; see Figure 21.1) are:
a) Thin (for 0.060" $ t $ 0.125"):
- [KM 7t d t FTY] /
(22.1) PNOT -
I .,fi
where:
(for 0.060" $ t < 0.080"):
KM = 0.80 (0.7) = 0.560
_ [t n A rs, Pru ]/
(22.2) PN OT -
.,fiI
c) Transition (for 0.125" < t < 0.25"):
(22.3)
2) The equations for spaced threads (screw-point types AB, B, BP, BF and BT; see chart) are:
a) Thin (for 0.038" $ t $ 2 / n), for spaced threads:
[Ku ndtFry]/
(22.4) PNOT -
-( )
.,fi I
where:
(for 0.038" ::: t < 0.080';:
Ku = 0.560
(22.5)
PNor = [0.9 ndtFru l I
I .,fi
(22.6)
As mentioned previously, the P NoT values are to be divided by k1 if this notch-sensitivity parameter exceeds 1.0 for the alloy
temper being considered. Refer to the 2010 ADM (Part l : table A.3.3 and Chapters D and F). The reduced PNOT values are
then to be divided by the appropriate safety factor S F· Unless noted otherwise, the tabulated values in this TIR are for alloy
tempers with k, = 1.0.
Predicted (nominal) values for fastener pull-out (PNor ), from the preceding equations, are divided by a safety factor (Sp ) in
order to detennine allowable values (P,. ). As discussed in Section 6.0, SF equals 3.0 for fasteners that are S 1/4" in
diameter, and Sp equals 2.5 for fasteners with diameters� 5/16". Specified or expected minimum values of tensile yield
and of ultimate tensile strength are used to determine allowable values for design. Since minimum values of yield and
ultimate strength are less than the average values, the resulting allowable (pull-out) strengths will typically be less than 1/SF
times the test values ofpull-out loads.
(22.7)
Using statistics to study the test results, some statements may be made about the expected variation in pull-out values of a
large number offasteners (ofa given size and type) from aluminum ofgiven thickness, alloy and temper. Given the mean
(X,-, ), sample standard deviation (s) and number ofsamples (y), an approximate "lower bound" value (XA ) can be determined
by the equation:
(22.8)
XA is the value which, with 95% confidence, is expected to be exceeded by 99% ofthe population. Refer to reference (3) for
the above formula for XA and a table ofvalues forK as a function ofy. See also references (1,2) for additional information
on statistical aspects.
If the coefficient ofvariation Cv (= 100% s/X,., ) is considered, in lieu ofsample standard deviation, then the equation for
XA can be written:
(22.9)
Review ofcoefficients of variation Cv for the pull-out tests indicates that the largest apparent value is 11.82% (series h97,
UNC, 5/16-18, 0.184" thickness). However, further review ofthis set of10 individual tests results indicates that two ofthe
individual pull-out values were an anomaly (very low, relative to the rest ofthis set's data). A likely explanation is that a
plate consisting ofa different alloy-temper was inadvertently mixed in with the other test plates for that set. With the
remaining eight tests, the value of Cv is 7.50%. For this reduced set oftests, y = 8, and thereforeK=4.353. Thus, for
Cv = 7.50%::
(22.10)
Given the preceding comments, the largest Cv is then 11.44% (series h97, Spaced Threads, #8-18, 0.0605" thickness). This
set has a more uniform distribution ofvalues. It is also more common for Cv values to be larger for thicknesses less than
about 1/8". For this set oftests:y= 10,K=3.981 andX,.= 0.5446XM.
Next consider a safety factor (Sp ) applied to the predicted (nominal) value ofpull-out (PNoT) to determine an allowable value
PA where: PA = (PNorfs ). Iftbe safety factor (Sp ) is considered equal to a load factor (m) divided by a resistance factor
p
(<p), then SF = m/<p. In other words, m TS <p PNor , where Tis the design tension per fastener and PA = PNor /(m/<p). A
safety-factor value of3.0 is required, for screws with diameters of l/4" and smaller, by both the cold-formed steel
speci fication (AISn and the aluminum specification (AA). For screws that are 5/16" diameter and larger, this TIR uses SF=
2.5, which equals or exceeds values used in the various material specifications that were reviewed. Refer to Section 6.0 for
discussion.
As given in ASCE 7, consider m =1.6 for live load. Thus, for Sp = 3.0, <p = m/SF = 1.6 / 3.0 = 0.533. Note that 0.533
is less than 0.5446, which equals XA /X,., , for the largest Cv (#8 ST screws, t = 0.0605", series h97). For SF = 2.5,
<p = 1.6 / 2.5 = 0.640. Note that 0.640 is less than 0.6735, which ms the value of XA /X,., for 5/16" diameter screws {UNC,
t = 0.184", series h97).
Therefore, ifthe "lower bound" variable XA 2!: cpX,., = 0.533XM for SF of3.0 (and XA 2!: 0.640X,., for SF of2.5), and if the
nominal value PNor :::; X,., , then 99% or more of the population offasteners are expected to be capable ofresisting a factored
tension forc.e equal to 1.6 times the allowable tension force. This perfonnance level is based on a particular fastener type and
diameter, a given base thickness, and a range oflocal mechanical properties (tensile yield and tensile ultimate) similar to that
in the corresponding set oftests.
The few cases which had predicted values ( PNor) greater than average tests values (X,., ) were at most 4.00% more than the
corresponding x,., . For those tests, the maximum Cv was 8.14% (series k89, Spaced Threads, #8-18, 0.088" thick). The
resulting values ofXA/X,., are at least 0.6759, which substantially exceeds cp ( = 0.533), which is the minimum desired value
ofXA /X,., for fasteners less than or equal to 1/4" diameter. In this case, XA /X,., is large enough to compensate for PNor =
1.04X,., because 0.6759/1.04 = 0.650, which exceeds 0.533.
Note that to establish design values ofallowable pull-out, the specified (or expected) minimum values ofyield and tensile
strength would be used. These values are generally significantly less than the corresponding average values. This means that
about 99% ofthe local (aluminum near the fastener) yield and tensile strengths, with a 95% confidence level, are expected to
equal or exceed the minimum values. Thus, the use of a design safety factor (Sp ) is expected to result in an actual safety
factor (for pull-out) which is significantly greater than SF, for the average piece of aluminum with a screw that is installed in
a tapped hole and loaded in tension.
References
I. ASTM volume 02.02, Aluminum and Magnesium Alloys, in the article "Statistical Aspects ofMechanical Property
Assurance" by W.P. Goepfert. Values for Kare taken from Juran's Quality Control Handbook, edited by Juran, J.M.,
4•h ed., published by McGraw-Hill, and are one-sided factors for 99% exceeding with a confidence of95%. (See also
Aluminum Design Manual, Part II [Commentary), Section A.3.2 for a discussion).
2. Miller and Freund's Probability and Statistics/or Engineers, 5�' ed., R. A. Johnson, Prentice-Hall, Englewood Cliffs,
NJ, 1994
4. Minimum Design wads for Buildings and Other Structures, ASCE 7-10, American Society of Civil Engineers
FIGURE 22.1: RELATIVE PLOT OF PULLOUT vs. BASE THICKNESS FOR UNC FASTENERS
5 0---------------1:J---------------o
Thin (Yield) Transition Thick (fhread Stripping)
i 4 .,
..
:5
Cl)
3
.....
Ci) @
::::,
C?
..J 2
..J
..
::::,
a.
1L1a
0
0
·:-----1----.---:-----10----.:-.
0.05 0.1 .125 0.15 0.2 025
----·l----:----'"I
0.3 0.35 0.4
BASETHICKNESS t !Inches
NOTE 20:
• Force units: Based on (rr DF,, /(3) 112) equal to tenJor relative scale,/oryieldregion I.
For strength region 3. assumed (Fu/Fy) = 22/16 = 1.3 75, TSA(l) = 0.017 in2/thread. and
N = 24 thread/in. lo gel ratio of threadshr. values lo baseyieldvalues.
5
Yield Transition Strength (of Threads)
·c:::::, 3
�
G)
� G) G) G) l-+- 01
0
..J
..J
2
::::,
Q.
0
0 0.05 0.1 .125 0.15 0.2 0.25 0.3 0.35 0.4
.038 0.08 BASE THICKNESS, t{lnches}
NOTE 21:
• Force units: Based on (n DFy/(3)112 ) equal to ten.for relative scale.for yield region 1.
For strength region 3, assumed (Fu!Fy) - 22116 = J.375for this plot.
3003-H14
TSA(I)
Nominal D Aluminum Thickness (Inches)
Internal
Thread Nominal
Thread
Diameter Thread 0.060 0.072 0.080 0.094 0.125 0.156 0.188 0.250 0.312 0.375
Stripping
& Thread Diameter
Area Sq.
Per Inch (Inch) Allowable Pullout (Pounds)
ln./Threa
#8-32 0.1640 0.010270 57 68 90 105 140 184 229 316 395 474
#10-24 0.1900 0.016864 66 79 104 122 162 219 277 389 486 584
#12-24 0.2160 0.019273 75 90 118 139 185 249 316 445 555 668
1/4-20 0.2500 0.027234 86 104 137 161 214 291 370 524 654 786
5/16-18 0.3125 0.037983 -- -- -- 241 320 437 557 789 985 1184
3/8-16 0.3750 0.051581 -- -- -- -- 384 525 671 953 1189 1429
7/16-14 0.4375 0.070205 -- -- -- -- -- 619 794 1135 1416 1702
1/2-13 0.5000 0.086405 -- -- -- -- -- 707 908 1297 1619 1946
3003-H14
--
Fu(Tensile Ultimate Strength)
Fv(Tensile Yield Strength)
20000
17000
psi
psi
L - - -
Shading indicates transition region. --
NOTE22:
1. Each table lists allowable pull-out (internal threads) values. S;� 3.0 for D � 0.25"; S; = 2.5 for D � 0.3125". Fastener allowable strength (basic tension and external threads)
needs to be checked separately.
2. For pilot hole sizes refer to tables 21.1 to 21.7
3. Fastener pullout not shown/or aluminum thickness less than approximately 2 threads, unless tested at a lesser thickness.
4. Multiple fastener connections and embrilllement need to be checked separately.
SOOS-H34
5005-H34
- --
C --
�
Fu {Tensile Ultimate Strength) 20000 psi --
Shading indicates transition region.
Fv(Tensile Yield Strength) 15000 psi
NOTE23:
1. Each table lists allowable pull-out (internal threads) values. SF = 3.0 for D � 0.25"; SF= 2.5 for D '?:. 0.3125". Fastener allowable strength (basic tension and external threads)
needs to be checked separately.
2. For pilot hole sizes refer to tables 21.1 to 21.7
3. Fastener pullout not shown/or aluminum thickness less than approximately 2 threads, unless tested at a lesser thickness.
4. Multiple fastener connections and embrilllement need to be checked separately.
6061-T6
TSA(I)
Nominal D Aluminum Thickness (Inches)
Internal
Thread Nominal
Thread
Diameter Thread 0.060 0.072 0.080 0.094 0.125 0.156 0.188 0.250 0.312 0.375
Stripping
& Thread Diameter
Area Sq.
Per Inch (Inch) Allowable Pullout (Pounds)
ln./Threa
#8-32 0.1640 0.010270 117 140 185 217 288 366 446 601 750 901
#10-24 0.1900 0.016864 135 162 214 251 334 435 539 740 923 1110
#12-24 0.2160 0.019273 154 184 243 286 380 495 615 846 1055 1268
1/4-20 0.2500 0.027234 178 213 281 331 440 578 720 996 1243 1494
5/16-18 0.3125 0.037983 -- -- -- 496 660 868 1083 1500 1872 2250
3/8-16 0.3750 0.051581 -- -- -- -- 792 1044 1305 1811 2260 2716
7/16-14 0.4375 0.070205 -- -- -- -- -- 1229 1545 2156 2691 3235
1/2-13 0.5000 0.086405 -- -- -- -- -- 1405 1766 2464 3076 3697
6061-T6
- - --
Fu (Tensile Ultimate Strength)
Fv(Tensile Yield Strength)
38000
35000
psi
psi
C Shading indicates transition region. ---
NOTE24:
1. Each table lists allowable pull-out (internal threads) values. SF = 3.0for D:: 0.25"; SF = 2.5for D � 0.3125". Fastener allowable strength (basic tension and external threads)
needs to be checked separately.
2. For pilot hole sizes refer to tables 21.1 to 21.7
3. Fastener pullout not shown/or aluminum thickness less than approximately 2 threads, unless tested at a lesser thickness.
4. Multiplefastener connections and embrittlement need to be checked separately.
6063-TS
6063-TS
-
F0 {Tensile Ultimate Strength) 22000 psi
psi
C- - -
Shading indicates transition region. -
Fv (Tensile Yield Strength) 16000
NOTE25:
1. Each table lists allowable pull-out (internal threads) values. Sp = 3.0 for D::, 0.25"; Sp = 2.5 for D � 0.3125". Fastener allowable strength (basic tension and external threads)
needs to be checked separately.
2. For pilot hole sizes refer to tables 21.l to 21.7
3. Fastener pullout not shown for aluminum thickness less than approximately 2 threads, unless tested al a lesser thickness.
4. Multiple fastener connections and embrittlemenl need to be checked separately.
��U::..,.������:��=��
arJljzation on Thu Maris 20,s.11 may
�=�:n'::'=��� by J.ll!il.ll!lllD.of Gbta• Nag (nstg{Stood
TABLE 22.5 (UNC)
6063-TG
TSA(I)
Nominal D Aluminum Thickness (Inches)
Internal
Thread Nominal
Thread
Diameter Thread 0.060 0.072 0.080 0.094 0.125 0.156 0.188 0.250 0.312 0.375
Stripping
& Thread Diameter
Area Sq.
Per Inch (Inch) Allowable Pullout (Pounds)
ln./Thread
#8-32 0.1640 0.010270 83 100 132 155 206 273 341 474 592 712
#10-24 0.1900 0.016864 96 116 153 180 239 324 413 584 729 876
#12-24 0.2160 0.019273 110 132 174 204 271 370 471 668 833 1001
1/4-20 0.2500 0.027234 127 152 201 236 314 431 552 786 981 1179
5/16-18 0.3125 0.037983 -- -- -- 354 471 648 831 1184 1478 1776
3/8-16 0.3750 0.051581 -- -- -- -- 565 780 1001 1429 1784 2144
7/16-14 0.4375 0.070205 -- -- -- -- -- 918 1185 1702 2125 2554
1/2-13 0.5000 0.086405 -- -- -- -- -- 1049 1354 1946 2428 2918
6063-TG
NOTE26:
I. Each table lists allowable pull-out (internal threads) values. SF= 3.0 for D !: 0.25"; SF= 2.5 for D � 0.3125". Fastener allowable strength (basic tension and external threads)
needs to be checked separately.
2. For pilot hole sizes refer to tables 2 I. I to 2 I. 7
3. Fastener pullout not shown/or aluminum thickness less than approximately 2 threads, unless tested at a lesser thickness.
4. Multiple fastener connections and embrittlement need to be checked separately.
6005A-T61
TSA(I)
Nominal D Aluminum Thickness (Inches)
Internal
Thread Nominal
Thread
Diameter Thread 0.060 0.072 0.080 0.094 0.125 0.156 0.188 0.250 0.312 0.375
Stripping
& Thread Diameter
Area Sq.
Per Inch (Inch) ln./Threa Allowable Pullout (Pounds)
#8-32 0.1640 0.010270 117 140 185 217 288 366 446 601 750 901
#10-24 0.1900 0.016864 135 162 214 251 334 435 539 740 923 1110
#12-24 0.2160 0.019273 154 184 243 286 380 495 615 846 1055 1268
1/4-20 0.2500 0.027234 178 213 281 331 440 578 720 996 1243 1494
5/16-18 0.3125 0.037983 -- -- -- 496 660 868 1083 1500 1872 2250
ll" 3/8-16 0.3750 0.051581 -- -- -- -- 792 1044 1305 1811 2260 2716
7/16-14 0.4375 0.070205 -- -- -- -- -- 1229 1545 2156 2691 3235
""
1/2-13 0.5000 0.086405 -- -- -- -- -- 1405 1766 2464 3076 3697
6005A-T61
NOTE27:
J. Each table lists allowable pull-out (internal threads) values. SF= 3.0 for D::: 0.25"; SF= 2.5 for D:::: 0.3125". Fastener allowable strength (basic tension and external threads)
needs to be checked
2. For pilot hole sizes refer to tables 16 to 22
3. Fastener pullout not shownfor aluminum thickness less than approximately 2 threads, unless tested at a lesser thickness.
4. Multiple fastener connections and embrittlement need to be checked separately.
5. For 6005-T5 and 6105-T5, divide pull-out values by 1.25. This k,factor is per 2010ADM (Table A.3.3., and Chapter D and F)
300�H14
3003-H14
C - -
� -
Fu(Tensile Ultimate Strength) 20000 psi Shading indicates transition region.
Fv (Tensile Yield Strength) 17000 psi
NOTE28:
1. Each table lists allowable pull-out (internal threads) values. Sp= 3.0 for D � 0.25"; Sp= 2.5for D;:: 0.3125". Fastener allowable strength (basic tension and external threads)
needs to be checked separately.
2. For pilot hole sizes refer to tables 21.1 to 21.7
3. Fastener pullout not shown for aluminum thickness less than approximately 2 threads, unless tested at a lesser thickness.
4. Multiple fastener connections and embrittlement need to be checked separately.
5005-H34
5005-H34
-
Fu (Tensile Ultimate Strength)
Fv (Tensile Yield Strength)
20000
15000
psi
psi
C Shading indicates transition region.
NOTE29:
1. Each table lists allowable pull-out (internal threads) values. Sp = 3.0 for D � 0.25"; Sp = 2.5for D � 0.3125". Fastener allowable strength (basic tension and external threads)
needs to be checked separately.
2. For pilot hole sizes refer to tables 21.l to 21.7
3. Fastener pullout not shown for aluminum thickness less than approximately 2 threads, unless tested at a lesser thickness.
4. Multiple fastener connections and embrittlement need to be checked separately.
AAMA TIR-A9-14
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Page 77
TABLE 22.9 (Spaced Threads)
6061-16
#8-18 0.1640 74 117 140 185 217 319 4S7 600 848 1058 1272
#10-16 0.1900 86 135 162 214 2Sl 334 49S 661 982 1226 1473
#12-14 0.2160 -- 154 184 243 286 380 512 700 1066 1393 1675
1/4-14 0.2500 -- 178 213 281 331 440 592 810 1233 1613 1938
5/16-12 0.3125 -- -- -- -- -- -- -- 1098 1732 2366 2908
3/8-12 0.3750 -- -- -- -- -- -- -- 1317 2079 2840 3489
6061-T6
-
C
-
Fu(Tensile Ultimate Strength) 38000 psi Shading indicates transition region. -
NOTE 30:
1. Each table lists allowable pull-out (internal threads) values. SF= 3. 0for D � 0.25"; SF= 2.5for D � 0.3125". Fastener allowable strength (basic tension and
external threads) needs to be checked separately.
2. For pilot hole sizes refer to tables 21.1 to 21.7
3. Fastener pullout not shown/or aluminum thickness less than approximately 2 threads, unless tested at a lesser thickness.
4. Multiple fastener connections and embrittlement need to be checked separately.
6063-TS
6063-TS
-
Fu (Tensile Ultimate Strength)
Fy (Tensile Yield Strength)
22000
16000
psi
psi
C -- - -transition region.
Shading indicates -
NOTE31:
1. Each table lists allowable pull-out (internal threads) values. SF = 3.0 for D � 0.25"; SF = 2.5 for D � 0.3125". Fastener allowable strength (basic tension and external threads)
needs to be checked separaJely.
2. For pilot hole sizes refer to tables 21.1 to 21.7
3. Fastener pullout not shown for aluminum thickness less than approximately 2 threads, unless tested at a lesser thickness.
4. Multiple fastener connections and embrittlement need to be checked separately.
6063-TG
#8-18 0.1640 53 83 100 132 155 235 350 468 669 835 1004
#10-16 0.1900 61 96 116 153 180 239 372 509 775 968 1163
#12-14 0.2160 .. 110 132 174 204 271 374 530 833 1100 1322
1/4-14 0.2500 .. 127 152 201 236 314 433 614 964 1273 1530
5/16-12 0.3125 .. .. .. .. .. -· ·- 809 1334 1860 2296
3/8-12 0.3750 .. .. .. -- .. .. -· 971 1601 2232 2755
6063-TG
C
-....------
NOTE32:
1. Each table lists allowable pull-out (internal threads) values. SF = 3.0 for D � 0.25"; SF = 2.5 for D '?:. 0.3125". Fastener allowable strength (basic tension and exJernal threads)
needs to be checked separately.
2. For pilot hole sizes refer to tables 21.1 to 21. 7
3. Fastener pullout not shown/or aluminum thickness less than approximately 2 threads. unless tested at a lesser thickness.
4. Multiple fastener connections and embrittlement need to be checked separately.
6005A-T61
#8-18 0.1640 74 117 140 185 217 319 457 600 848 1058 1272
#10-16 0.1900 86 135 162 214 251 334 495 661 982 1226 1473
#12-14 0.2160 -- 154 184 243 286 380 512 700 1066 1393 1675
1/4-14 0.2500 -- 178 213 281 331 440 592 810 1233 1613 1938
5/16-12 0.3125 -- -- -- -- -- -- -- 1098 1732 2366 2908
3/8-12 0.3750 -- -- -- -- -- -- -- 1317 2079 2840 3489
6005A-T61
--
Fu (Tensile Ultimate Strength)
Fy {Tensile Yield Strength)
38000
35000
psi
psi
C - -
Shading indicates transition region.
NOTE33:
J. Each table lists allowable pull-out (internal threads) values. SF ... 3.0 for D � 0.25"; SF ... 2.5 for D 2:: 0.3125". Fastener allowable strength (basic tension and external threads)
needs to be checked separately.
2. For pilot hole sizes refer to tables J 6 to 22
3. Fastener pullout not shown for aluminum thickness less than approximately 2 threads, unless tested at a lesser thickness.
4. Multiple fastener connections and embrittlement need to be checked separately.
5. For 6005-T5 and 6105-T5, divide pull-out values by 1.25. This krfactor is per 20JOADM(I'able A.3.3., and Chapter D and Chapter F).
EXAMPLE l
Anchorage components shown in the figure below must resist 600 lbs wind load, acting inwardly or outwardly, applied
horizontally along the edge of the 6 in long, 1/4 in thick extruded 6063-T6 aluminum Z-shape. Using two bolts spaced 2 in
apart, 2 in from the ends of the shape, select a suitable fastener of SAE Grade 2 carbon steel from Table 20.2, which covers
loads for this grade of steel.
_____,T
Pwl = 600 lbs.
1.125"
Referring to Table 20.2, as a first try, select a fastener which can meet one-half of the actual 600 lb shear load (V). A
1/ - 20 fastener provides a 398 lb allowable single shear load V and a 785 lb allowable tension load (T ). The single shear
4 A A
load is adequate. Now check the actual tension load (7).
600(1.125) 600(1.125)
T= = = 1350 lbs
y(O.S) 0.5
y == 1.0 in this example. y is a factor which approximates the increase of stresses in the fastener due to deformations (elastic
and/or plastic) in attached materials. Commonly, the range� 0.67 :s; y � 1.0 is used based on the engineer's judgment.
COMMENT: If in this example the attachment was made to wood, then y == 0.67 might be more appropriate and such
analysis would require reassessment of fastener size.
=
2TA 2(758) 1570 =
1579lbs > 1350lbs
The tension load is adequate, but it is now necessary to check the adequacy of the fastener to resist the combined tension and
shear loads. The Combined Stress Ratio (CSR) is calculated using the interaction e quation 7.6 from Section 7.0.
2 2
1 350/ 600/
CSR = ( 2) + ( /) = 0.739 + 0.568 = 1 .307
785 39
This is greater than 1.0 and, therefore, not adequate. Try the next larger size bolt, 5/16 - 18. From Table 20.2 we find
allowable tension, TA= 1,552, allowable shear VA= 801 lbs., and nominal diameter, d = 0.3125".
2
1350/ 600/ 2
CSR = ( 2 ) + (801 2) = 0. 89 + 0.140 = 0.329
1
l,552
This is less than 1.0 and is, therefore, adequate. Note, however, that there is minimal clearance between the bolt head (or
washer) and web of the Z.
Inasmuch as this connection is made with two bolts, washers and nuts, there is no need to check the pull-out resistance.
Minimum distance between bolt centers is 2.5 times the nominal diameter, (d) for aluminum; 3 times the nominal diameter is
preferred for steel. For the 5/16-18 bolt, 2.5d = 2.5(.3125) = 0.781 in; 3d = .938 in. Bolts in this example are spaced 2 in
apart, which is satisfactory. Refer to Section 8 for information on minimum spacing and minimum edge distance for both
steel and aluminum.
Minimum edge distance for aluminum; 1.5d = 1.5(0.3125) = 0.469 in. For hole 1/32" larger than bolt, actual distance is 0.484
in (= 0.5" - [1/32 ")/2), which is adequate. Note that an edge distance of2d is needed for full allowable bearing.
Finally, the bearing loads (Section 8.0) on both the steel and aluminum components must be checked.
PA8 (A36 steel) = (2 bolts)(l.2)( 5/16)( 1/4 )(58 ksi) = 10,875 lbs total
484 3
P,. 6063 - T6 - [ (O. "(O.ZS ")( 0 ksi))/, 95]- 1,862 lbs P" bolt - 3,724 lbs tntal
( ) .
The allowable bearing for both the steel and aluminum components is much greater than the required 600 pounds.
Alternates:
Try �-20 (Gr. 5): VA = 646 lbs and TA = 1,273 lbs per bolt,
CSR = 0.497 < 1.0, OK
Try #12-24 (Gr. 5): VA = 493 lbs and TA = 967 lbs per bolt,
CSR = 0.857 < 1.0, OK
The #12 fastener is the most efficient choice and provides the most clearance.
Anchorage components shown in the figure below must resist a horizontal wind load (Pw ) of2,400 lbs, acting either inward
or outward, and a dead load (P0 ) of 1,200 lbs. To resist these loads, select suitable bolts from Table 20.9 that are made of
stainless steel (alloy groups 1, 2 and 3; condition CW). Check the mullion through-bolts for shear and the mullion for bolt
bearing. Bending in the through bolts will be neglected in this example because the 1/32" thickness of the spacers is less than
half of the bolts' effective diameter at the threads. The anchor-to-structure bolts (used as screws installed in tapped holes)
will be evaluated for shear, tension and bearing loads.
MULLION
(6063-T5 ALUM TUBE,
1/8" WALLS) BOLT INTO
TAPPED HOLE
PLAN VIEW IN 1/2" STEEL
1" 5"
1"
P w = 2,400 LBS
� ... 2"
1"
ANCHOR
SIDE VIEW
STRUCTURE
A) Find the resultant shear at each shear plane of the through bolts.
From Table 20.9, the 1/8" thick wall of the 6063-T5 aluminum mullion has an allowable bearing load of 688 lbs at a 3/8-16
bolt. This exceeds the design load of 671 lbs. For shear, the bolt has an allowable single-shear load equal to 1,614 lbs, which
exceeds the 671 lbs design shear load.
From the same table, the allowable bearing for 1/8" A36 steel is 2,447 lbs. For the 1/4" thick A36 steel plates, the allowable
bearing load is thus (0.25 / 0.125)(2447) = 4,894 lbs per shear plane. This is conservative (see Section 8.0 for t> 3/
16").
C) Check the edge distance (center to edge) and spacing (center to center).
Referring to Section 8.0 (comments after Eq. 8.2), pertaining to the allowable bearing values in the tables, the edge distance
(e) in the wind load direction for a bolt bearing on steel must not be less than 1.8 d, which is 1.8 (0.375") = 0.675". This is
less than I" provided and so is satisfactory. In the dead load direction, the minimum edge distance is also 1.8 d = 0.675",
which is less than I" provided (okay). From Section 8.0 (comments preceding Table 8.1), the preferred minimum bolt
spacing for steel (t > 3/16") is 3 d, which is 3 (0.375") = 1.125" < 2" provided, which is adequate.
Referring to Section 8.0, the minimwn bolt spacing for aluminum is 2.5 d, which equals 2.5 (0.375") = 0.938". This is less
than the 2" spacing provided and thus is satisfactory.
Table 23.2: SUMMARY: (2) 3/8-16 BOLTS [STAINLESS STEEL: ALLOY GROUPS 1, 2 & 3; CONDITION CW]
A) Determine the forces in each bolt, due to dead load and wind load. Refer to Figure 23.2 for this example.
Vo= 1200/2 = 600 lbs per bolt; (Shear due to dead load)
= =
tw 2400/2 1,200 lbs per bolt; (Tension due to outward wind load)
Use a factor (y) to account for the centroid location of the compression reaction, due to eccentricity of the dead load, below
the bolts. Assume a rectangular strip for the compression zone whose bottom edge is approximately flush with the anchor's
bottom edge. To limit the contact stress and allow for flatness tolerances, use y = 0.95. Depending on the connected
materials and engineering judgment, y may range from 0.67 (e.g., a triangular stress distribution) to slightly less than 1. Thus
the tension due to the eccentric dead load can be determined as follows:
NOTE 35: In this example, due to the bending strength of the 3/4" thick anchor plate, there is no prying to cause added
tension in the bolts. See the calculation procedure in the AISC Manual (14th ed., pages 9-10 and 9-1 /), for angle-like
connecting elements.
Referring to Table 20.9, a 1/2-13 bolt has an allowable single shear of 2,984 lbs (exceeds 600 lbs per bolt and so is
satisfactory) and an allowable tension of 5, 676 lbs (greater than 2,779 lbs per bolt and thus okay). Because shear and tension
act on each bolt simultaneously, it is necessary to check the combined stress ratio (CSR). This interaction may be calculated
using Eq. 7.6 (last equation in Section 7.0):
csR =
2
(t 2
= ( 600 iz984) 2 2779
2
= 0.040 + 0.240 = 0.280 < 1.0
lrA ) + ( /5676 )
( )
v/vA +
This is less than 1.0 and is thus adequate. Using Table 20.9, the bearing and pull-out allowable values can also be checked.
For 1/8" thick A3 6 steel, this bolt (1/2-13) has an allowable bearing load of 3,26 3 lbs. For 1/ 2 " thick A3 6 steel, the allowable
bearing is (0.5'' / 0.125") (3263) = 13,052 lbs. This exceeds 600 lbs per bolt and is acceptable. The allowable value is
conservative (see Section 8.0 for t> 3/16"). Table 20.9 also lists allowable tension values for fasteners installed in tapped
holes in 3/8" thick steel, which is less than the 1/2" thickness provided. For this bolt, the allowable pull-out is 5, 642 lbs,
which exceeds 2,779 lbs and is adequate.
C) Check the edge distance (center to edge) and spacing (center to center)
Refe rring to Section 8.0 (comments after Eq. 8.2), the edge distance (e) in the dead load direction for a bolt must not be less
than 1.8 d: 1.8 (0.5'') = 0.90" < 2" provided, which is satisfactory. Based on Table 8.1, the minimum edge distance (eM),
from the hole center to the edge that is parallel to the load, must be at least 3/4". This is less than the l " dimension provided
and is adequate.
Referring to the comments prior to Table 8.1, the preferred minimum bolt spacing for steel is 3 d: 3 (0.5'') = 1.5". This is
less than 6.0625" provided, which is adequate.
Table 23.3: SUMMARY: (2) 1/2-13 BOLTS [STAINLESS STEEL: ALLOY GROUPS 1, 2 & 3; CONDITION CW]
Clearly, the 1/2-13 bolts are conservative for this example. An additional iteration of design would find that certain smaller
fasteners (i.e., 7/16-1 4 and 3/8-16) are also adequate, but loaded much closer to their allowable values.
24.0 APPENDIX (Screw Engagement in Screw Chase; Sliding Friction in Screw
Chase; Thread Root Area)
DERIVATION OF EQUATION FOR DETERMINING SCREW ENGAGEMENT IN SCREW CHASE (per thread)
b b
Ath Ae/2
Referring to Figure 24.1 we find the area of the screw thread engagement, (A e ) to be:
(24.1)
But,
(24.2, 24.3)
(24.4)
(24.5)
Thus,
(24.6, 24.7)
(24.8)
Ratio of engaged thread area to total thread area then becomes:
(24.9, 24.10)
But,
(24.11)
So that,
(24.12)
Then:
(24.13)
Equation (24.14) below, considering friction for screws with V-threads in threaded round holes, is taken from Chapter 3 of
Mark's Mechanical Engineers' Handbook.
H/8
- ,A ' '•
··.:_,. 17H/24
··.· . · .. .. ·: . .
.... , -
.,
H
: :'.:: _::.}\::
R
•.
FIGURE24.2
where:
c = � the angle between the faces ofa thread, (degrees)
F = Tensile force exerted by tightening screw, in screw chase (lb.)
f = Coefficient of friction. For mild steel on aluminum, f = 0.47.
P = Pitch ofscrew, 1/N = Pitch, (in.)
R = Major radius ofscrew thread, (in.)
r = Minor radius of screw thread, (in.)
Re = Ratio ofarea of screw thread engagement in screw chase from Equation 24.13.
rm = mean radius of screw thread, (in.)= (R + r)/
2
Vs/ = Ultimate lateral frictional resistance to sliding of a screw in a screw chase parallel to walls (length) of
chase, (lb.). Shear factor for determining resistance of screw in screw chase parallel to walls (length) of chase,
(lb.).
But,
(24.16) !?.!!.
24
= (R - r)
So that,
(24.17) H = (24/17)(R - r)
NOTE 36: The equations from the original published document have been updated to the following simplified
forms.
(24.18)
[(24 ) (R r)] ( 2 p) 2
secc J r7 -+ 2
(ii) (R -r)
Also,
(24.19)
j [( �)(R-r)f +(8.SP) 2
secc =
(24)(R -r)
(24.20) S = secc
(24.21)
(24.22)
(24.23)
(24.24)
i}
C
v---
h
P/2
C 30·
h = 60 °
The ultimate lateral frictional resistance as given by Equation 24.22 is used to determine the shear strength of a screw in a
screw chase when loaded parallel to the walls (length) of the screw chase. Equation 24.22 is expressed in terms of the torque;
the major, mean and minor radii of the screw; the pitch of the screw; and the coefficient of friction between the fastener metal
and the aluminum extrusion. To determine an allowable design value, divide V5 1 by a suitable safety factor. A safety factor of
2.34 is recommended.
17 0.866 1.2269
K=D-2 ( )( ) =D---.(in.)
24 � N
1.2269 2
TC (D --N-)
(v --
2
1.2269
A(R) = Thread Root Area = = 0.7854 --) , (sq. in.)
4 N
25.0 APPLICABLE DOCUMENTS
25.1 References to the standards listed below shall be to the edition indicated. Any undated reference to a code or standard
appearing in the requirements of this standard shall be interpreted as to referring to the latest edition of that code or standard.
"Aluminum Design Manual, Part 1, Chapter J - Specification for Aluminum Structures", 2010
"North American Specification for the Design of Cold-Formed Steel Structural Members", - 2007
ANSI/ASME B1.1-2003, Unified Inch Screw Threads (UN and UNR Thread Forms)
25.1.SASTM International
ASTM Al 43/Al43M-07, Standard Practice for Safeguarding Against Embrittlement of Hot-Dip Galvanized Structural Steel
Products and Procedure for Detecting Embrittlement
ASTM Al 53/Al 53M-09 Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware
ASTM A 307-12, Standard Specification for Carbon Steel Bolts, Studs, and Threaded Rod 60 000 PSI Tensile Strength
ASTM A325-10el Standard Specification for Structural Bolts, Steel, Heat Treated, 120/105 ksi Minimum Tensile Strength
ASTM A449-l O Standard Specification for Hex Cap Screws, Bolts and Studs, Steel, Heat Treated, 120/105/90 ksi Minimum
Tensile Strength, General Use
ASTM A490-12 Standard Specification for Structural Bolts, Alloy Steel, Heat Treated, 150 ksi Minimum Tensile Strength
ASTM A563-07a Standard Specification for Carbon and Alloy Steel Nuts
ASTM B20 l-80(2009)e 1 Standard Practice for Testing Chromate Coatings on Zinc and Cadmium Surfaces
ASTM B456-l l e l Standard Specification for Electrodeposited Coatings of Copper Plus Nickel Plus Chromium and Nickel
Plus Chromium
ASTM B633-13 Standard Specification for Electrodeposited Coatings of Zinc on Iron and Steel
ASTM B695-04(2009) Standard Specification for Coatings of Zinc Mechanically Deposited on Iron and Steel
ASTM F593-13a Standard Specification for Stainless Steel Bolts, Hex Cap Screws, and Studs
ASCE/SEI 7-10, "Minimum Design Loads for Buildings and Other Stnictures", 2010
ASCE/SEI 8-02, "Specification for the Design of Cold-Formed Stainless Steel Stnictural Members", 2002
12295-200605, Fastener Part Standard - Cap Screws, Hex Bolts and Hex Nuts (Inch Dimensioned)
DA TE: 3/2/2015
CODE: TIR-A9-14
TITLE: Design Guide for Metal Cladding Fasteners
RATIONAL:
In the text following equation (10.19) an error occurred in the equation for P8 • The "t" variable was mistakenly
placed in equation. This errata corrects that mistake and moves the "d" variable toward the beginning of the
equation to align with the format of the preceding equations.
RATIONAL:
An typo was made in both TSA{I) and TSA(E) equations. (3) y, should have been 1/(3) 112
•
Copy,ighl by the Amer1can Archlle<:lural Manufacturers Association (AAMA). This document was purchased by J.Ql'i of Ch,oaNatl Inst of s1aooardlzat100 on ThU Mar 102010. t may
not be reproduce<l, repubtiSMd or dislribuled In any fon-nal w,u=t t11e express wntlen cons&nt ot AAMA