COST ACTION TU0601...Institut Für Konstruktion und Entwurf Prof. Dr.-Ing. Ulrike Kuhlmann,...
Transcript of COST ACTION TU0601...Institut Für Konstruktion und Entwurf Prof. Dr.-Ing. Ulrike Kuhlmann,...
Institut Für Konstruktion und Entwurf
Prof. Dr.-Ing. Ulrike Kuhlmann, Dipl.-Ing. Lars Rölle
COST ACTION TU0601Robustness of Structures
Workshop Coimbra 02./03. March 2009
Ductility of connections - a measure to improve redundancy
Prof. Dr.-Ing. Ulrike Kuhlmann, Dipl.-Ing. Lars Rölle
Institut Für Konstruktion und Entwurf
Prof. Dr.-Ing. Ulrike Kuhlmann, Dipl.-Ing. Lars Rölle
Redundancy within the structural system by alternate load pathsRedundancy within the structural system by alternate load paths
Alternate load path method
strengthening of one/more floors design of joints with sufficiently d til b h i d
Alternate load path method
ductile behaviour and activation of membrane forces
→ causes usually much extra costs → less extra costsd d f ll d i d→ demands for well-designed
connections2
Institut Für Konstruktion und Entwurf
Prof. Dr.-Ing. Ulrike Kuhlmann, Dipl.-Ing. Lars Rölle
Alternate load path methodAlternate load path method
alternate load paths may be achieved by various measures
bending capacity
plastic reserves bearing-mechanism structural behaviour
σ
actual values
σy
2D
fy,d
fy,cnominal values
actual values
σy uniaxial
ε
material hardening
tension capacity
3Dg
σy
3D
spatial
requires sufficient available ductility of members and joints3
Institut Für Konstruktion und Entwurf
Prof. Dr.-Ing. Ulrike Kuhlmann, Dipl.-Ing. Lars Rölle
Ductility demands to allow the activation of bearing reservesDuctility demands to allow the activation of bearing reserves
plastic material reserves plastic system reserves
large plastic strain change of bearing mechanismcatenary action
large global and local deformations
DUCTILITY
ductility of members ductility of jointsy y j
4
Institut Für Konstruktion und Entwurf
Prof. Dr.-Ing. Ulrike Kuhlmann, Dipl.-Ing. Lars Rölle
Type of connections influence the global resistance of the structureType of connections influence the global resistance of the structure
type of joints are usually the weakest link beam-to-column connectionin a framed structure
special focus
rigid partial-strength pinned
M M M M M M
N
MjMbeam
Φ
MjMbeam
N
Mj
Mbeam
Φ
Mj
Mbeam
N Φ
suitable but expensive suitable not suitable lack of resistanceN Φ N Φ N Φ
⇒ by adequate resistance and sufficient ductility 5
Institut Für Konstruktion und Entwurf
Prof. Dr.-Ing. Ulrike Kuhlmann, Dipl.-Ing. Lars Rölle
Why is sufficiently ductile joint behaviour so important?Why is sufficiently ductile joint behaviour so important?
M M
→ no redistribution possible → plastic redistribution possible
Φ Φ
6 hinge is located in the joint ⇒ high requirements concerning joint deformability
Institut Für Konstruktion und Entwurf
Prof. Dr.-Ing. Ulrike Kuhlmann, Dipl.-Ing. Lars Rölle
Influence of over strength effectsInfluence of over-strength effects
Over-strength effectsmaterials
b ff tmembrane effects
Adjustment of single componentsweakest components always ductile
oversizing of the bolts
avoiding premature brittle bolt failure with limited ductility of the joint7
Institut Für Konstruktion und Entwurf
Prof. Dr.-Ing. Ulrike Kuhlmann, Dipl.-Ing. Lars Rölle
Influence of over strength effectsInfluence of over-strength effects
Influence to the relevant component
M M Mductile component brittle component connectionM M Mductile component brittle component connection
nominal values Φ1 Φ2 Φ1+Φ2+ =Φ1 Φ2 Φ1+Φ2+ =
Φ Φ ΦcdΦ Φ Φcd
M M Mductile component brittle component connectionM M Mductile component brittle component connection
actual values + =+ =
Φ Φ ΦΦcdΦ Φ ΦΦcd
actual values of material strength may limit the deformation capacity clearly 8
Institut Für Konstruktion und Entwurf
Prof. Dr.-Ing. Ulrike Kuhlmann, Dipl.-Ing. Lars Rölle
Influence of over strength effects on resistance and ductility
Influence on the moment-rotation-curve
Influence of over-strength effects on resistance and ductility
IPE 500, M24 10.9, t=15 mm500
Bolf & fBolf & f
400
[kN
m] Boltmax+EPmax
Boltmax+EPmit
B l EP iΔM
Bol
Bol
Bol
fuB,(μ+σ) & fy,(μ+σ)
fuB,(μ+σ) & fy,(μ)
fuB,(μ+σ) & fy,(μ-σ)
f & f
Bol
Bol
Bol
fuB,(μ+σ) & fy,(μ+σ)
fuB,(μ+σ) & fy,(μ)
fuB,(μ+σ) & fy,(μ-σ)
f & f
200
300
nmom
ent [ Boltmax+EPmin
Boltmit+EPmax
Boltmit+EPmit
Boltmit+EPmin
ΔM(μ)
ΔM(μ+σ)
ΔM(μ-σ)
Bol
Bol
Bol
fuB,(μ) & fy,(μ+σ)
fuB,(μ) & fy,(μ)
fuB,(μ) & fy,(μ-σ)
Bol
Bol
Bol
fuB,(μ) & fy,(μ+σ)
fuB,(μ) & fy,(μ)
fuB,(μ) & fy,(μ-σ)
mom
ent
100Kno
te
Boltmit EPmin
Boltmin+EPmax
Boltmin+EPmit
Boltmin+EPmin
Bol
Bol
Bol
fuB,(μ-σ) & fy,(μ+σ)
fuB,(μ-σ) & fy,(μ)
fuB,(μ-σ) & fy,(μ-σ)
Bol
Bol
Bol
fuB,(μ-σ) & fy,(μ+σ)
fuB,(μ-σ) & fy,(μ)
fuB,(μ-σ) & fy,(μ-σ)
m
00 10 20 30 40 50 60 70
Knotenrotation [mrad]
ΔΦ(μ)ΔΦ(μ-σ) ΔΦ(μ+σ)
rotation
small influence on the resistance, clear influence on the rotation capacity9
Institut Für Konstruktion und Entwurf
Prof. Dr.-Ing. Ulrike Kuhlmann, Dipl.-Ing. Lars Rölle
Influence of over strength on the structural response
structural response under service conditions
Influence of over-strength on the structural response
kNm
]
Required rotation at support
oint
mom
ent [
mean value
5% - value
95% - value
depends on bending resistanceof member and joints that dependon material strength
required rotation [mrad]
jo
Variation of material strength influence also structural response10
Institut Für Konstruktion und Entwurf
Prof. Dr.-Ing. Ulrike Kuhlmann, Dipl.-Ing. Lars Rölle
Probabilistic analysis to assess sufficient rotation capacity
M determintion off structural steel
Probabilistic analysis to assess sufficient rotation capacity
M determintion ofM- Φ-curve
f
fyf
stochastic distribution of strength
structural steel
boltsΦavai
Φavaifu,B
strength
Φavai - Φreq = Zequation of limit state
Z < 1t ti
M
qf live loadstochastic
distribution of loads
Φreq
rotation not
sufficient
Φ
method to assess the geometrical criteria for sufficiently ductile joint behaviour11
Institut Für Konstruktion und Entwurf
Prof. Dr.-Ing. Ulrike Kuhlmann, Dipl.-Ing. Lars Rölle
Redundancy by allowing force redistributionRedundancy by allowing force redistribution
requires large deformations
Φ
demands for sufficient resistance (M-N), beside ductility
N N
activation of alternate load paths requires joint ductility and sufficient M-N resistance13
Institut Für Konstruktion und Entwurf
Prof. Dr.-Ing. Ulrike Kuhlmann, Dipl.-Ing. Lars Rölle
Experimental test simulation of steel and composite jointsExperimental test simulation of steel and composite joints
Steel Joint Tests Composite Joint Tests
bending test
M
bending and tension
M
Φ
M-Φ-curve
N
M-N-Interaction
determination of requirementsand design criteria for
highly ductile behaviour
NM
M-Φ-curvehighly ductile behaviour
14
Φ
for hogging and sagging moment
Institut Für Konstruktion und Entwurf
Prof. Dr.-Ing. Ulrike Kuhlmann, Dipl.-Ing. Lars Rölle
Composite joints under bending and tensionComposite joints under bending and tension
Test results
80V1 nt
M-phi-curve M-N-interaction1
20
40
60
kNm
]
V1V2V3V4V5
ggin
g m
omen
0,2
0,4
0,6
0,8
m]
-40
-20
00 100 200 300 400 500 600 700
Mom
ent [
k
g m
omen
tsa
g
0 6
-0,4
-0,2
0-70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70M
[kN
m
Joint Rotation V1Joint Rotation V2
-80
-60
Normal Force [kN]
hogg
ing
-1
-0,8
-0,6
phi[mrad]
Joint Rotation V3Joint Rotation V4Joint Rotation V5
→ Joints have been able to follow the whole M-N-curve from pure bending state
to pure tension state due to sufficient ductility
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Institut Für Konstruktion und Entwurf
Prof. Dr.-Ing. Ulrike Kuhlmann, Dipl.-Ing. Lars Rölle
Joint tests confirmed by a Substructure testJoint tests confirmed by a Substructure test
Φavai
[Substructure test
Liége]Liége]
structural response allows force redistribution by activation of membrane effects 16
Institut Für Konstruktion und Entwurf
Prof. Dr.-Ing. Ulrike Kuhlmann, Dipl.-Ing. Lars Rölle
OutlookOutlook
further numerical and experimental investigations are planned
stress
P(t)t1t
strain
P(t)t2t3
straindetermination high stress-strain rates
of plates and bolts component response under high velocity
P(t)component response under high velocity
loadingrotation capacity and strength?
including additional bearing effects3D effects
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Institut Für Konstruktion und Entwurf
Prof. Dr.-Ing. Ulrike Kuhlmann, Dipl.-Ing. Lars Rölle
Thanks for attention !Thanks for attention !
Universität StuttgartInstitut für Konstruktion und EntwurfSchwerpunkte: Stahlbau, Holzbau und VerbundbauProf Dr -Ing Ulrike KuhlmannProf. Dr. Ing. Ulrike KuhlmannDipl.-Ing. Lars RöllePfaffenwaldring 770569 StuttgartGermany
Tel. +49 711 685 66245Fax +49 711 685 66236Fax +49 711 685 [email protected]