07_Eurocodes_Steel_Workshop_WEYNAND.pdf

Design of Structural
Steel Joints
Dr. Klaus Weynand
Feldmann + Weynand GmbH, Aachen, Germany
Prof. Jean-Pierre Jaspart
University of Liège, Belgium

Design of Structural
Steel Joints
• Introduction
• Integration of joints into
structural design process
• Moment resistant joints
• Simple joints
• Design tools

Eurocodes - Design of steel buildings with worked examples Brussels, 16 - 17 October 2014
EN 1993 Part 1.8
Chapter 1 – Introduction
Chapter 2 – Basis of design
Chapter 3 – Connections made with bolts, rivets or pins
Chapter 4 – Welded connections
Chapter 5 – Analysis, classification and modelling
Chapter 6 – Structural joints connecting H or I sections
Chapter 7 – Hollow section joints

Design of simple joints
ECCS Publication No 126 (EN)
• Background information
• Design guidelines

2 – Basis of design  Partial safety coefficients

3 – Connections made mechanical fasteners

4 – Welded connections

Actual joint response

Actual joint response
M

M Rd
S j,ini
cd

Influence on the structural response
• Displacements
• Internal forces
• Failure mode and failure load

M

M

?
?
?
M

Characterization
Modelling
Classification
Idealization
Four successive steps for structural integration

Characterization
Search for a unified approach whatever the material
M

?
?
?

Various configurations (1)
Continuity
Beam-to-beam
Column bases

Joints in portal frames

Connections and joints in
composite construction

Various cross-section shapes (1)
Hot-rolled and
cold-formed

Various cross-section shapes (2)
Built-up profiles

Various connection elements
Splices
Cleats
End plates

Economy
Reduced fabrication, transportation and erection costs



Specific design criteria
Robustness
 Joints as key elements

Characterization (1)
Search for a unified approach
M

?
?
?

Characterization (2)
Eurocode 3 – Part 1-8
• Beam-to-beam joints, splices, beam-to-column joints and column
bases:
 welded connections
 bolted connections (anchors for column bases)
Background: COMPONENT METHOD

Three steps
First step
Identification of the
active components
Second step:
Response of the
components
Third step:
“Assembly” of the
components
F F F
E k1 E k2
E k3
F1,Rd
F2,Rd
F3,Rd
  
column web
in shear
column web
in tension
column web
in compression
M
Sj,ini
Mj,Rd
cd
 
, ,
min
j Rd i Rd
M F z
 
2
,
1
j ini
i
E z
S
k



Characterization (3) - component method

Characterization (4) - component method
EC3 Part 1-8 provides therefore:
• a library of components
• rules for the evaluation of the properties of the components
(stiffness, resistance, deformation capacity)
• rules for the evaluation of the possible component interactions
• « assembly » rules for components
Applicable for simple joint and moment resistant joint

Characterization (4) – Hollow section joints
Different approach for lattice girder joints
For many types of joint configurations:
• Joints considered as a whole
• Check of relevant failure modes
• Scope of application to be checked

Classification (1)
Stiffness
Sj,ini

Pinned
Semi-rigid
Rigid
Mj
Boundaries for stiffness
Joint initial stiffness
Semi-rigid
Rigid
Pinned
Classification boundaries
Initial joint stiffness

Classification (2)
Resistance
Mj,Rd
Partial-strength
Full-strength
Pinned

Mj
Boundaries for strength
Joint strength
Full resistance
Partial resistance
Pinned
Classification boundaries
Joint resistance

Classification (3)
Ductility
• Brittle
• “Semi-ductile”
• Ductile

Mj

Modelling
JOINT
MODELLING
BEAM-TO-COLUMN JOINTS
MAJOR AXIS BENDING
BEAM
SPLICES
COLUMN
BASES
SIMPLE
SEMI-
CONTINUOUS
CONTINUOUS

Example
Single sided beam-to-column joint configuration, bolted end-plate connection
+ +
+ +
M
V
15
3
IPE220
HEB140
120
60 10
80
30 30
240
4 M16 8.8
140
u=10
p=60
5
w=
To be evaluated:
Design moment resistance , initial stiffness
0
1
1,0
1,0
M
M




Material: S 235

General data
2 2 140 2 12 2 12 92
wc c fc c
h h t r mm
        
 
  2
2 2
4295,6 2 140 12 7 2 12 12 1307,6
vc c c fc wc c
A A b t t r
mm
   
        
80 7
0,8 0,8 12 26,9
2 2
fc
c
w t
m r mm
 
     
140 80
30
2 2
c
b w
e mm
 
  
2 2
,
0
12 235
0,25 0,25 8460 /
1,0
fc yc
pl fc
M
t f
m Nmm mm


  
Column
Equivalent T-stub in tension
F /4
t
Ft
F /4
t
F /4
t
F /4
t
m e
leff

General data
+ +
+ +
15
3
IPE220
120
60 10
80
30 30
240
4 M16 8.8
140
u=10
p=60
5
w=
z
9,2
220 10 60 165,4
2 2
fb
b
t
z h u p mm
        
6
,
,
0
285.406 235 10
(classe 1 section) 67,07
1,0
pl yb yb
c Rd
M
W f
M kNm


 
  
Lever arm
Beam

General data
2 2
,
0
15 235
0,25 0,25 13.218 /
1,0
p yp
pl p
M
t f
m Nmm mm


  
mp
mp2
80 5,9
0,8 2 0,8 2 3 33,66
2 2
wb
p w
w t
m a mm
 
      
2 0,8 2 60 10 9,2 0,8 2 5 35,14
p fb f
m p u t a mm
         
140 80
30
2 2
p
p
b w
e mm
 
  
End plate

General data
5,5
 
1
33,66
0,53
33,66 30
p
p p
m
m e
   
 
2
2
35,14
0,55
33,66 30
p
p p
m
m e
   
 
Alpha factor for effective lengths
End plate

General data
3
,
0,9 0,9 800 157 10
90,43
1,25
ub s
t Rd
Mb
f A
F kN


  
  
3
,
0,6 0,6 800 157 10
(shear plane in thread) 60,3
1.25
ub s
v Rd
Mb
f A
F kN


  
  
   
1
0,5 12 15 10 14,8 2 4 47,4
2
b fc p bolt nut
L t t h h mm
          
Bolts

Component No 1 – Column web in shear
Vwp
Vwp

F
M
z
F
3
,
,
0
0,9 0,9 1307,6 235 10
159,7
3 3 1,0
vc y cw
wc Rd
M
A f
V kN


  
  

Assumption : 1
 
,
,1
159,7
159,7
1
wc Rd
Rd
V
F kN

  
1
0,38 0,38 1307,6
3,004
1 165,4
vc
A
k mm
h


  

Resistance
Stiffness coefficient
Transformation parameter

Component No 2 – Column web in compression
   
   
, , min 2 2 2 5 ; 2 5
min 9,2 2 5 2 2 15 5 12 12 ; 9,2 5 2 15 10 5 12 12 161,27
eff c wc fb f p fc fb f p fc
b t a t t s t a t u t s
mm
 
         
 
 
               
 
, ,
Assumption : min 1,0; 1,7 / 1,0
wc com Ed y wc
k f

 
  
 
, , ,
2
161,27 92 235
0,932 0,932 0,543 0,673 1,0
210000 7 7
eff c wc c y wc
p
wc
b d f
Et
 
 
     
 
   
1 2 2
, ,
1 1
0,713
1 1,3 161,27 7 1307,6
1 1,3 /
eff c wc wc vc
b t A
 
   
 

3
,2 , , , 1
/ 1 0,713 1 161,27 7 235 10 1,0 189,1
Rd wc eff c wc wc y wc M
F k b t f kN
  
        
Resistance
Reduction factors to account for compression stresses and instability

Component No 2 – Column web in compression
F

F k E
i i i
 
, ,
2
0,7 0,7 161,27 7
8,589
92
eff c wc wc
wc
b t
k mm
h
 
  

Component No 3 – Column web in tension
   
, , min 2 ;4 1,25 min 2 26,9;4 26,9 1,25 30 145,10
eff t wc
b m m e mm
 
       
   
1 2 2
, ,
1 1
0,749
1 1,3 145,1 7 1307,6
1 1,3 /
eff t wc wc vc
b t A
   
 

3
,3 , , , 0
/ 0,749 145,1 7 235 10 1,0 178,7
Rd eff t wc wc y wc M
F b t f kN
  
      
, ,
3
0,7 0,7 145,1 7
7,728
92
eff t wc wc
wc
b t
k mm
h
 
  
Resistance

Equivalent T-stub in tension
Component No 4 – Column flange in bending
Component No 5 – End plate in bending
F /4
t
Ft
F /4
t
F /4
t
F /4
t
m e
leff

T-stub – Effective length
Distinction between circular and non-circular yield line patterns
Circular patterns Non-circular patterns

Groups effects to consider in addition to the individual response of each bolt-row
Group 1+2 Group 2+3 Group 1+2+3
Row 1
Row 2
Row 3

Groups effects to consider in addition to the individual response of each bolt-row
Row 3
,3 ,3, ,3,
;
( )
Rd Rd indiv Rd group
F min F F


Bolt rows considered
In this example: only bolt row 1 is considered for tension forces
+ +
+ +
M
V
15
3
IPE220
HEB140
120
60 10
80
30 30
240
4 M16 8.8
140
u=10
p=60
5
w=
Row 1
Row 2

, , , , 145,1 (see column web in tension)
eff t fc eff t wc
l b mm
 
   
min ;1,25 ; / 2 min 30;1,25 26,9;30 30
p
n e m b w mm
 
    
 
Resistance

3
, , , , 3
, , 2
2 2 2 145,1 8460 2 90,4 10 30
10 138,5
26,9 30
eff t fc pl fc t Rd
fc Rd t
l m B n
F kN
m n

      
   
 
, , 3 ,
2 2 90,43 180,9
fc Rd t t Rd
F B kN
   
Mode 1 - Complete yielding of the flange
Mode 2 - Bolt failure with yielding of the flange
Mode 3 - Bolt failure
, , , 3
, , 1
4 4 145,1 8460
10 182,5
26,9
eff t fc pl fc
fc Rd t
l m
F kN
m

 
   

,4 , , 1 , , 2 , , 3
min ; ; 138,5
Rd fc Rd t fc Rd t fc Rd t
F F F F kN
 
 
 
3 3
, ,
4 3 3
0,9 0,9 145,1 12
11,59
26,9
eff fc t fc
l t
k mm
m
 
  
Resistance

 
, , min 2 ; min 2 33,66; 5,5 33,66 185
eff t p p p
l m m mm
  
 
    
 
 
min ;1,25 ; min 30;1,25 33,66;30 30
p p p
n e m e mm
 
   
 
, , , 3
, ,1
4 4 185 13.218
Mode 1: 10 291
33,66
eff t p pl p
ep Rd
p
l m
F kN
m

 
   
3
, , , , 3
, ,2
2 2 2 185 13.218 2 90,43 10 30
Mode 2: 10 162,1
33,66 30
eff p t pl p t Rd p
ep Rd
p p
l m B n
F kN
m n

      
   
 
,5 , ,1 , ,2 , ,3
min ; ; 162,1
Rd ep Rd ep Rd ep Rd
F F F F kN
 
 
 
Resistance

3 3
, ,
5 3 3
0,9 0,9 185,0 15
14,73
33,66
eff t p p
p
l t
k mm
m
 
  

Component No 7 – Beam flange and web in compression
 
,7 , 3
67,07
/ 318,2
210,8 10
Rd c Rd b fb
F M h t kN

   

7
k 
Resistance

Component No 8 – Beam web in tension
, , , , 185
eff t wb eff t p
b l mm
 
3
,8 , , 0
/ 185 5,9 235 10 1,0 256,5
Rd eff t wb wb yb M
F b t f kN
 
     
8
k 
Resistance

Component No 10 – Bolts in tension
,10 ,
2 2 90,43 180,9
Rd t Rd
F B kN
   
10
157
1,6 1,6 5,30
47,4
s
b
A
k mm
L
   
 Mode 3 in T-stubs for components:
• “column flange in bending”
• “end plate in bending”
Resistance

Mj,Rd
Design moment resistance
,
min 138,5 (Column flange in bending)
Rd Rd i
F F kN
 
 
 
3
, 138,5 165,4 10 22,91
j Rd Rd
M F z kNm

    
, , ,
2
15,27
3
j el Rd j Rd
M M kNm
 
Design plastic moment resistance
Relevant component
Design elastic moment resistance

Stiffness

Sj,ini
2 6
2
,
210000 165,4 10
/ 1 6234 /
1 1 1 1 1 1
3,004 8,589 7,728 11,59 14,73 5,30
j ini i
i
S E h k kNm rad

 
  
    

, / 2 3117 /
j j ini
S S kNm rad
 
Initial stiffness
Secant stiffness

Design moment-rotation characteristic

M
Sj,ini
Sj,ini
Sj
Sj
= /
Ersatzsteifigkeit:
Mj,Rd
2/3Mj,Rd
Secant stiffness

Nominally pinned joints
Braced frame

Nominally pinned joints
V  0 M = 0

Classification and modelling of joints
Limits for classification of joints by stiffness

Nominally pinned
Semi-rigid
Rigid
Mj
Initial stiffness of the joint
Sj,ini <<
“Nominally pinned” joints :

Sj,ini
Limits for classification of joints by stiffness

Nominally pinned
Semi-rigid
Rigid
Mj
Initial stiffness of the joint
“Semi-rigid” joints :

As an alternative to a semi-continuous modelling (semi-rigid joints), is it safe to
model the joints as nominally pinned whilst they are actually semi-rigid?
Semi-rigid Sj,ini > 0,5EIb/Lb
Partial strength Mj,Rd > 0,25 Mfull-strength
Nominally pinned Sj,ini = 0
Nominally pinned Mj,Rd = 0
??

Yes, …under the reservation the joint has:
• a sufficient rotation capacity
= capacity to “rotate”
• a sufficient ductility
= capacity to follow the actual
loading path in a ductile way
VRd
V
M
Yielding criterion
MRd
Supposed
loading path
Actual loading
path

Supplementary design requirement
Sufficient resistance to «catenary effects» so as to provide required structural
robustness

Example: Partial depth end-plate
Components
• Bolts in shear
• End-plate in bearing
• End-plate in shear (gross section)
• End-plate in shear (net section)
• End-plate in shear block
• End-plate in bending
• Beam web in shear
• Welds in shear
• Column flange in bearing

Partial depth end-plate
Strength requirement
• Use of “component method” for the assessment of VRd
Assessment of the strength of all the constitutive
components of the joint
+
“Assembly” of these components

Rotation capacity requirement
Bending moment
Rotation
avail
Contact between
supported beam and
supporting element
Compression force
Bending
moment
Bolts in tension

Rotation capacity requirement
hp
he
tp
hb
db
avail
p b
h d

p
avail
e
t
h
 

Ductility requirement
• Prevent premature fracture of the bolts
• Prevent premature fracture of the welds
under unavoidable bending moment in the joint

Ductility requirements
• Prevent premature collapse of the bolts
2,8 yp
p ub
f
d
t f

2,8 ycf
p ub
f
d
t f
 for the supporting column
d and fub : diameter and tensile strength of bolts
for the end-plate
Yielding of end-plate prior to tensile fracture of bolts

Practical design tools
• Tables of standardized joints
• Dedicated software

Worked Example Configuration
 Beam IPE 500
 Column HEA 340
 End plate connection
Design assumption
 Rigid joint
Frame analysis
 MEd = 220 kNm
CoP software used for this example: http://cop.fw-ing.com

Design resistance: MRd = 196 kNm < 220 kNm
Classification: Semi-rigid
Failure mode: Column web in compression

Failure mode:
End plate in bending

Failure mode:
Column web panel in shear

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