design of steel tension connections
TRANSCRIPT
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Advantages of Bolts
Does not require as highly skilled workers
Requires less equipment
Reduced risk of fire Better quality control
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Types of Connections by Bolt Action
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Bolt Holes(Sizes in Table J3.3) p. 16.1-62
Standard
Oversized
Short-slotted
Long-slotted
Connection types
Bearing
Slip-critical
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Spacing, Edge and End Distances
Maximums
Center to Center (pitch) 24 x thickness
of thinner part 12 Edge distance 12 x thickness of part 6
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Bolt Shear Strength
J3.6FnAb Table J3.2
FnTable J3.2
AbArea of bolt
Tabulated on page 7-33, Table 7-10
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Bearing Strength at Bolt Holes
J3.10 Rn 0.75
Rngiven by equations J3-2
Tabulated on page 7-34,35
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Analysis of Tension Connection
Example (p. 15 notes)
Two A36 steel plate tension membershave been connected with a lap spliceusing diameter A307 bolts,arranged as shown. Find theallowable service live load. Also findrequired distances a and b. Assume
service live load is two times deadload. Plate edges are likely to besheared.
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Analysis of Tension Connection
Example (p. 15 notes)
P P
a a3 in.
10 in.
P
P
3/8 in.
3/8 in.
b
b
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Bolt Design Example p. 16 notes
Design a pair of splice plates to
connect the two parts of the channel
tension member shown. The forcesin the member are 110 kips live load
and 69.7 kips dead load. The bolts in
the surrounding joints are 1diameterA325N. All steel is A36. Slip is not
critical.
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Bolt Design Example p. 16 notes
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Block Shear Rupture
J4.3Equations J4-3a and J4-3b
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Welded Tension Connections
Two primary types of welds:
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LRFD Specification for Welds
p. 16.1-52
Effective throat thickness = 0.707 x
Where = weld size or leg size
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Limitations on Fillet Welds
Minimum weld sizeTable J2.4
Maximum weld size:
along edge of material < thick= thickness of material
along edge of material > thick= material thickness - 1/16
Minimum length Greater than 4 x weld size and,
If longitudinal filet welds are used alone in endconnections of flat bar tension members length perpendicular distance between them (p. 16.1-234)
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Limitations on Fillet Welds
Intermittent fillet weld segments must be atleast 4 times the weld size and 1
Lap joints require a lap of at least 5 times
the thickness of the thinner part joined, butnot less than 1 in. (p. 16.1-235)
Returns are required when practicable at
the ends of fillet welds. The must be atleast 2 times the weld size and usually notmore than 4 times the weld size.
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Design Strength of WeldsTable J2.5 p. 16.1-57
Fillet welds (shear on effective area):
Where:
Aw= Area of weld = throat thickness x length
FEXX=Weld metal designation(FE70 = 70 ksi)
Welded connection design procedure p. 22 notes
))(60.0)(75.0( wEXXww AFAF
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Weld Design Example p. 22 notes
An L 6 x 4x is stressed in tension by a 50
kip live load and a 40 kip dead load. At
the truss panel point the angle member is
attached to a 5/8thick gusset plate. The4 leg of the angle is outstanding. Check
the angle for tension strength and design
the welded connection of the angle to theplate. Assume all material is A36 steel
and that the loading will be static.
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Weld Design Example p. 22 notes