Download - Gusset Plate Design
Lecture Notes #28Design of Gusset plate
1
Professor Guowei MaOffice: 160
Tel: 61-8-6488-3102Email: [email protected]
Gusset Plate
2
• Flat structural elements used to connect adjacent
members meeting at truss panel joints and at diagonal
brace connections.
• Help transmit loads from one member to another.
• Maybe welded or bolted to the members meeting at the
joints.
• Minimum thickness used in design practice is usually 10
mm.
Gusset Plate at a Diagonal Brace
3
Gusset Plate at a Truss Panel Point
4
Gusset Plate at a Truss Panel Point
5
Gusset Plate at a Truss Panel Point
6
Gusset Plate at a Truss Support
7
Design of Gusset Plate
8
• For diagonal bracing connection, several connection
interfaces must be designed:
diagonal brace-to-gusset connection
gusset-to-column connection
beam-to-column connection
• At truss joints, the gusset plates connect the web
members to the chord members
• The centroidal axes of the members meeting at the joint
coincide at one point, called the work point (WP)
Design of Gusset Plate
9
• Moment may be induced in the gusset plate and the
adjoining members if it is not feasible to have a common
WP
• Shear and axial stresses
• Whitmore effective width, lw Projecting lines at an angle of spread of 30˚ on both
side of the connection starting from the first row of bolts
to the last row of bolts
For welded connections, projected on both sides of the
longitudinal weld to the end of the weld
Design of Gusset Plate
10
• Effective gross area
Whitmore effective width, lw times the plate thickness, t
• End of the bracing member or truss web member
terminates at least a distance of 2t away from the re-
entrant corner of the gusset plate at the gusset-to-column
interfaces
• Above requirement can be relaxed for connections subject
to monotonic or static loading
Out-of-Plane Buckling
11
• Unbraced length, Lg
the larger of the length of the plate between adjacent
lines of bolts parallel to the direction of the axial
compression force, or the length of the plate along the
centroidal axis of the diagonal brace or truss web
member between the end of the brace or truss web
member and the connected edge of the gusset plate.
• Buckling is assumed to occur over a plate width equal to
the Whitmore effective width, lw
Out-of-Plane Buckling
12
tlN wcrc φσφ =
lw: Whitmore effective width
t: Thickness of the gusset plate
Φ: 0.9
σcr: The critical buckling stress
Buckling of the Free or Unsupported Edge
13
Buckling of the Free or Unsupported Edge
14
Ef
Lt yfg5.0≥
• Gusset plate under monotonic or static loading
• Gusset plate subject to cyclic (or seismic) loading
Ef
Lt yfg33.1≥
Yielding of Gusset Plate
15
Tension yielding is the most desirable form of failure because of the ductility associated with this failure mode
tlfN wys φφ =
• Design tension or compression yield strength
Tension Failure
16
Tension failure of the gusset plate due to fracture at a bolt line within the Whitmore effective area
tndlfN holewus )( −=φφ
plategusset theofstrength Tensile : uf0.75 : φ
lineeach for force axial applied the lar toperpendicu holesbolt ofNumber : n
holebolt ofDiameter : holedLeast desirable form of failure because of the sudden and brittle nature of this failure mode
Combined Actions
17
0.12*2**
≤
+
+
sss VV
NN
MM
φφφ
Example
18
For the truss joint shown below, the gusset plate is made of
Grade 400 steel with a yield stress fy= 400 MPa, and tensile
strength fu=520 MPa assuming a M20 bolts of Property Class
4.6, determine
i) Whitmore effective width for the gusset plate on diagonal
web members A and B
ii) Compression buckling capacity of the gusset plate on
diagonal member A
iii)Tension capacity of the gusset plate on diagonal member B
19
16 mm thick
Gusset plate
271 kN
271 kN
376 kN
20
75 mm
40
Solution
21
1)
mm 6.20630tan1508040
tan40
=°++=
++= θwAAwA Lbl
mm 2.25330tan150280
tan2
=°×+=
+= θwBBwB Lbl
22
2) mm 75=gL
433 mm 5.70519)16)(6.206(121
121
=== tlI wAA
mm 62.4)16)(6.206(
5.70519===
AIr A
A
2.1662.4
75==
A
g
rL
75 mm
206.6 mm
kN 24721N 104721.2
)1075()105.70519)(10200(14.3
7
23
1292
2
2
=×=
×××
== −
−
ecr l
EIN π
kN 22249247219.0 =×== crc NN φφ
23
3)
kN 4.1458
)102.253)(1016()10400)(9.0( 336
=
××××== −gyt AfN φφ
Tension yielding capacity of the gusset plate on the diagonal element B
Tension capacity of the gusset plate due fracture
kN 5.133110)2222.253)(1016()10520)(85.0)(9.0(
85.0336
=××−×××=
=−−
uut AfN φφ