lecture notes 11 design of plate girder
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Lecture Notes #11Design of Plate Girder
1
Professor Guowei Ma
Office: 160
Tel: 61-8-6488-3102
Email: [email protected]
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Plate Girder
2
• A plate girder is a beam built up from plate elements to
achieve a more efficient arrangement of material than is
possible with rolled beams.
• Plate girders are economical where the spans are long
enough to permit saving in cost by proportioning for the
particular requirements.
• Plate girders may be of riveted, bolted, or welded
constructions.
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Difference between Beam and Girder
3
• A plate girder is actually a deep beam. The limit states with
regard to beams are still applicable for plate girders.
• All rolled W (wide-flange shapes) have “compact” webs and
only a few sections have “non-compact” flanges.
• When the web is “non-compact” or “slender”, provisions
should be given to account for local and bend-buckling of
the web.
• In general, plate girder webs are typically “slender”.
• The flexural and shear strengths of a plate girder are largely
related to the web.
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Transfer Plate Girders – Plan View
PLATE GIRDER
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PG5-C
PG5-BC
PG5-BC
Floor Framing SystemSteel transfer structures; plate girders PG5-A, PG5-BC & PG5-C
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Plate Girder PG5-C- girders of more than 5m deep and with spans of up to 27m
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Design of Plate Girders
Efficient design thick flanges and thin deep webs
-but web cannot be so thin that serviceability and
flange buckling are affected
a
dt
T
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Section SlendernessClause 5.2.2
For a section with flat compression plate elements, the
section slenderness (λ s) shall be taken as the value of the
plate element slenderness (λ e) for the element of the
cross-section which has the greatest value of λe/ λ ey
Read carefully Clause 5.2.2
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Design of WebUnstiffed webs
• web shear
• combined shear and bending
• web buckling
• web bearing.
Stiffened webs:
• transverse, intermediate stiffener proportioning
• end stiffeners
• end posts
• axial loads on stiffeners
• longitudinal stiffeners.
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Minimum Web ThicknessClause 5.10.1, 5.10.4, 5.10.5, 5.10.6
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Shear Capacity of WebsClause 5.10.2
Aw : the effective area of the web: Aw = (d1 – dd ) t w
d1 : the clear depth of the web,
dd : height of any holes up to a height of 0.1d1 for
unstiffened webs (0.3d1 if web is stiffened) and
tw : is the web thickness.
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Buckling Capacity of Unstiffed Web
Clause 5.11.5.1
Method of stiffening
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Shear and bending interaction for
unstiffened webs
Clause 5.12.2, 5.12.3
for
αvm: Reduction factor in shear capacity
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Bearing Capacity of Unstiffed Web
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Bearing Capacity of Unstiffed Web
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Bearing Capacity of Unstiffed Web
• Bearing yield capacity (Clause 5.13.3)
where bs is the length of the stiff bearing, tf the flange
thickness and bd is the remaining distance to the end of the
beam.
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Bearing Capacity of Unstiffed Web
• Bearing buckling capacity (Clause 5.13.4)
The nominal bearing buckling capacity (Rbb) of a web
without transverse stiffeners shall be taken as the axial
load capacity determined in accordance with Section 6
(Members subject to Axial Compression) using αb equals
0.5 and kf equals 1.0 for a compression member of area
twbb and slenderness ratio le/r equals 2.5d1/tw where bb is
the total bearing width obtained by dispersions at a slope
of 1:1 from bbf to the neutral axis, if available, as shown in
Figure 5.13.1.1.
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Bearing Capacity of Unstiffed Web
• Bearing buckling capacity (Clause 5.13.4)
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Design of Load Bearing Stiffeners
• Bearing yield capacity (Clause 5.14.1)
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Rsb = the nominal buckling capacity of the stiffened web,
determined in accordance with Section 6 using b
equals 0.5 and kf equals 1.0 for a compression
member whose radius of gyration is taken about the
axis parallel to the web.
Design of Load Bearing Stiffeners
• Bearing buckling capacity (Clause 5.14.2)
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Design of Load Bearing Stiffeners
• Bearing buckling capacity (Clause 5.14.2)
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Torsional End Restraints
(Clause 5.14.2)
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Design of Intermediate Transverse
Stiffeners
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Design of Intermediate Transverse
Stiffeners
• Minimum area (Clause 5.11.3)
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Design of Intermediate Transverse
Stiffeners
• Buckling capacity (Clause 5.11.4)
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Connection to Web(Clause 5.15.8)
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End Posts(Clause 5.15.8)
αv : given in Clause 5.11.5.2
Vw : given in Clause 5.11.4
e : distance between the end plate and load bearing
stiffener.
When an end post is required, it shall be formed by a load
bearing stiffener and a parallel end plate. The load bearing
stiffener shall be designed in accordance with Clause 5.14,
and shall be no smaller than the end plate. The area of the
end plate (Aep) shall satisfy
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Design of Longitudinal Web Stiffeners
(Clause 5.16)