Transcript Design of Beam-Column Connections in Steel Moment Frames

Design of Beam-Column Connections in Steel Moment
Frames
Observed Damage to Steel Moment Frames in the 1994
Northridge Earthquake
Observed Damage to Steel Moment Frames in the 1994
Northridge Earthquake
Typical Moment Frame Connection Detail Prior to 1994
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Prequalified Connection Detail by FEMA 350
Welded Unreinforced Flanges, Welded Web
Connection (WUF-W)
Welded Unreinforced Flanges, Bolted Web
Connection (WUF-B)
Recommended Weld Access Hole Detail
Typical Details of the Joint Panel Zone Continuity Plate and Column Web Doubler Plate
Design Procedure of the WUF-B Connections
Beam-Colum Connection Recommended in GB500112001: WUF-B Connection – Beam Parallel to
Column Web
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Column through, joint panel zone in the column
The 2 welds between the beam flanges and the columns flange must be CJP
groove welds
The beam web to column flange connection by high strength friction grip bolts
via a column connection plate
The weld between the column flange and the column connection plate shall be
fillet weld both sides, >=5mm, and to develop the full shear strength of the
connection plate. If the plate exceeds 16mm in thickness, use double bevel
CJP groove welds
Continuity plates and beam flanges equal thickness and equal strength
Beam-Colum Connection Recommended in GB500112001: WUF-B Connection – Beam Perpendicular to
Column Web
Design Process – Step 1 Design Connection for
Bending
• Mu >= 1.3Mp
• Mp = full plastic moment capacity of the
plastic hinge of the beam (column
through), or of the column (beam through)
• Mu = Bending moment resistance capacity of
the joint connection provided by the
flange connections and based on the
design strength of connection
• If column through and if CJP groove welds
are used to connect the beam flanges to
the column, this overtrength requirement
is considered met
Eurocode 8 Provisions
Design Process – Step 2 Design Connection
for Shear
• Vu >= 1.2(2Mp/ln)+VGb
• Mp = full plastic moment capacity of the
plastic hinge of the beam (column
through), or of the column (beam through)
• ln = clear span of beam
• VGb=(seismic weight UDL)ln/2, shear force
at beam ends, determined by considering
static equilibrium of the isolated beam
under the seismic weight UDL
• Vu = Shear resistance capacity of the
joint connection provided by the web
connection and based on the design
strength of connection
Design Process – Step 3 Calculate the Required
Panel Zone Thickness and Determine if a Doubler
Plate is Needed
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The shear stress in the panel
zone bounded by the flanges
of the column and the
continuity plates shall meet
t = y(Mpb1 + Mpb2)/Vp<=4fyv/3,
as well as t = (Mb1 +
Mb2)/Vp<=(4/3)fv/gRE
Vp = hbhctp is the volume of
the panel zone, tp is the
panel zone thickness >=(hb +
hc)/90
y = 0.6 for Seismic
Resistance Class 3 and 4, 0.7
for Seismic Resistance Class
1 and 2
Mb1 and Mb2 = the factored
bending moments of beams at
the two sides of the joint
panel
gRE=0.75
f = design shear strength of
Beam-Column
Joint Panel
Zone
Doubler
Plate if
Required
Design Process – Step 4 Design the Shear
Tab and the HSFG Bolts
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To resist the connection shear force demand
1.3(2Mp/l)
FEMA 350 recommends that the bolts should be
designed for bearing
Chinese code recommends the following for checking
the shear resistance of HSFG bolts: Nvb = 0.75nAnbfub
Nvb = shear resistance provided by one HSFG bolt
n = number of cross sections resisting shear in the
bolt
Anb= net cross section area of bolt
fub = tensile strength of bolt material