Stability behaviour of non- conventional cold-formed steel ... · cold-formed steel structures ESMC...

Department of Structural EngineeringBudapest University of Technology and Economics

Stability behaviour of non -conventional

cold -formed steel structures

ESMC 2009 September 7-11, 2009, Lisbon

László Dunai Gábor Jakab

Professor Asst. Professor

Budapest University of Technology and Economics

Department of Structural Engineering


„Non -conventional”

Cold-formed sections fabrication; new generation of products

Novel structural functions in buildings

New structural arrangements


New structural arrangements

Design rules ?

Experimental research and development

DESIGN


Section types combined sections

Eccentricities eccentric section arrangements in joints

eccentric load introduction on section elements

Non-conventional arrangements


Connections connectors, contacts

Lateral supports discrete position; partial rigidity


section section

connection structural

element

Interaction


element

structural element joint

Stability behaviour ?


Frame



Frame – application



Truss



Truss – application



FE model

EXPE

DE

Pilot test

Verification test

FE simulation

Research methodology

Analysis

Virtual


ERI

MENT

ESIGN

Validation test

Design test

Prototype test

Design method

Struct. details

Design value

Virtual experiment


Structural element and connection

Structural joint

Research strategy


Structural joint

Global structure


Structural element and connection C-section, screw connection

Research strategy


Structural joint

Global structure truss


Fundamental research on element behaviour

Subject of the research– centric/eccentric compression– combined built-up sections– load introduction– lateral restraints

C-section structural elements


– lateral restraints

Aims– stability behaviour– failure mode identification– FE model development, verification, application– design method development, validation


Experimental program


• 10 different section and end connection arrangements• 98 tests• C150/1.0 – C200/2.5

– web b/t: 80-200• Specimen lengths

– 800, 1500, 2000, 2500, 3600 mm


Test preliminary design



Single C -section elements



Element end failure


Short screw layouton web

Stub column –web connection

Load introduction at the whole section end


Screw arrangement – web/flange



Screw arrangement – web



„I-section” elements



Single double section



„Hollow” section elements


Tension and compression side C or U loaded


Behaviour modes



Laterally supported elements



Software : ANSYS

Element : SHELL181 (4-node, 24 DOF’s)

Material model : linear elastic – hardening

plastic

Single C -section element FE model


plastic

Contact surfaces : CONTA173/TARGE170

Self-drilling screw model :

– „beamstar”; BEAM4

– calibrated stiffness parameters

Model size : ~ 100000 DOF’s (L=2500 mm)

Contact surfaces

Shank elementRadial elements


cFSM analysis pure modes FE model

Geometrical imperfections



20

40

60

80

100

120

FE

res

ista

nces

[kN

]

FE analysis


00 20 40 60 80 100 120

Test resistances [kN]


EC3-1-3:1996y = 0.975x

R2 = 0.98

EC3-1-3:2006y = 0.9777x

R2 = 0.9596

Rt = Rd

100

120

140

160

180

200

Des

ign

resi

stan

ces

(Rd)

[kN

]Single section element resistances


0

20

40

60

80

100

0 20 40 60 80 100 120 140 160 180 200

Test resistances (R t) [kN]

Des

ign

resi

stan

ces

(R

1996 2006 Rt = Rd EC3-1-3:1996 trend EC3-1-3:2006 trend


1

8.0

,

8.0

,

≤

∆++

Rdb

EdEd

Rdb

Ed

M

MM

N

N

1/

)(

/ 0,,

,,

0min

≤⋅

∆+⋅+

⋅⋅ Mcomzeffyb

EdzEdzz

Meffyb

Ed

Wf

MM

Af

N

γκ

γχ nomEdEdz eNM ⋅=,

nomee ⋅= 4.1mod

Sye ⋅≥ 4.0mod

EC3-1-3:1996

EC3-1-3:2006

Buckling – bending design resistance


( ) ( ) 165.065.0

,,≤+ ∆+

Rdb

EdEd

Rdb

Ed

MMM

NN

Sye ⋅≥ 4.0mod


αγ

κγχ

≤⋅

∆+⋅+

⋅⋅ 1,,

,,

1min /

)(

/ Mcomzeffyb

EdzEdzz

Meffyb

Ed

Wf

MM

Af

N

Section type α

Double section design resistance


I column 0.8·L+1.0, L – element length [m]

CC 1.8

CU1.3 – C-section loaded1.8 – U-section loaded

I brace 2.5


Subject of the research– full-scale truss experimental study– different structural elements– different joints

Aims

C-section truss


Aims– interacting stability behaviour– failure mode identification– FE model development, verification– design method validation


failure in the upper

Test #1


failure in the upper chord, interaction

of bending and flexural buckling


failure in the lower chord

Test #5/1


failure in the lower chord

joint nearest to the supportinteraction of shear and

tension


failure of the upper chord; interaction of bending and

Test #5/2


interaction of bending and flexural buckling


30

40

50Lo

ad [k

N/ja

ck]

Load -deflection relationship


0

10

20

0 20 40 60 80 100Deflection [mm]

Load

[kN

/jack

]

Test No. 1 Test No. 2 Test No. 3 Test No. 4 Test No. 5


Truss FE model

Software : ANSYS

Element : SHELL181 (4-node, 24 DOF’s)

Material model : linear elastic –

hardening plastic

Contact surfaces :


Contact surfaces :

CONTA173/TARGE170

Bolt model :

– modified „beamstar”; BEAM4

– calibrated stiffness parameter

Imperfections : selected eigenmodes

Model size : ~ 1.400.000 DOF’s

Shank element

Rigid radial link

Radial beam element


Eigenmodes – imperfections



FE analysis – joint failure1 2


12


FE analysis – chord buckling



1/

)5.0(

/

)(

/ 1,,

,,

1,,

,,

1min

≤⋅

∆+⋅⋅+

⋅⋅∆+⋅

+⋅⋅ Mcomzeffyb

EdzEdzz

McomyeffybLT

EdyEdyLT

Meffyb

Ed

Wf

MM

Wf

MM

Af

N

γκ

γχκ

γχ

Compression chord: single section resistance --- reduced out-of-plane eccentricity

Brace: single and I-section resistance

Design method

N-joint : shear resistance and interaction of joint and chord member


N-joint : shear resistance and interaction of joint and chord member

5

,,

3 M

effvywRdb

AfV

γχ

⋅⋅⋅

=

( ) ( ) 52

,,,,0,0 //1 MRdbEdyeffvyeffveffRd VVfAfAAN γ

−⋅⋅+⋅−=


Research methodology: from experiments to design of non-

conventional cold-formed steel structures.

Experiments on C-section elements: test results for a wide range of

arrangement (section, load introduction); modified stability behaviour

modes.

Concluding remarks


FE model for screwed members: screw model, cFSM pure mode

imperfections, calibration, test domain extension.

Development of cold-formed structures: truss, frame, purlin,

composite floor beam; experimental and numerical research.

Global advanced FE model: development, verification, applicability.

Design methods: experimental and numerical validation of modified

and/or new application rules for the structural elements, joints and

structure.



Thank you for your attention!

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