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Structural Behaviour of

High Performance Steel

Structures in Seismic Area

Ms. Paola Pannuzzo

Dr. Junbo Chen

Dr. Tak-Ming Chan

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1. Introduction

2. Methodology

3. Results and Discussions

4. Concluding remarks

OUTLINE

1

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1. Strength

2. Stiffness

3. Ductility

1. High Strength –to- weight ratio

2. High torsional stiffness

3. Yes/ No?

REQUIREMENTS

FOR SEISMIC APPLICATIONS

CHARACTHERISTICS

OF HOT-FINISHED HOLLOW STEEL

SECTIONS

Introduction

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DUCTILITY

Capacity of a mechanical system (structure or member

or material) to deform in the plastic domain ( after yield

point) without reducing its bearing capacity.

PDuctility = Deformation capacity

Yield Point

Δ𝒖Δ𝒚

Failure

Introduction

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Manufacturing process

Hot-finished Cold-formed

• Homogeneity • Non-homogeneity

• Consistent hardness • Enhanced strength

• Good ductility • Less ductility

• Low residual stresses • High Residual stresses

• Hot-Finished

• Cold-Formed

MATERIAL DUCTILITY

Ability of steel to resist large plastic strains

Cold-Formed

Introduction

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MEMBER DUCTILITY = ROTATION CAPACITY

Key Parameters : b/t , d/t

• EUROCODE 8

GLOBAL DUCTILITY LOCAL DUCTILITY GLOBAL DUCTILITY LOCAL DUCTILITY

• AISC 341-16

Introduction

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• 12 specimens, with different width-to-thickness ratios (b/t), depth-to-thickness

ratios (d/t) with similar member slenderness (L/r).

• All specimens were tested under monotonic as well as cyclic loading.

• The section sizes were chosen so as to provide a sufficient scatter of b/t and d/t

values with regard to the limits provided by AISC 341-16 for highly, λhd , and

moderately, λmd, ductile members.

TEST MATRIX

Methodology

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EXPERIMENTAL SETUP

• Three-point bending test arrangement

• Monotonic tests were carried out

under displacement control

• SAC loading protocol was adopted

to apply the lateral cyclic load

Methodology

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FAILURE MODES

Flange local buckling

Flange and Web local buckling

Fracture before local buckling

Fracture after local buckling

Results and discussions

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(i) Highly ductile members

• Despite both achieved high rotation levels with no moment degradation,

rectangular sections attained lower over-strength as well lower rotation

levels than square sections with similar b/t ratio

Section b/t d/t L/r

Ductile

criteria

(AISC 341-

16)

100x100x6.3 13.6 13.6 23.1 Highly

120x120x6.3 16.2 16.2 21.3 Moderately

150x150x5 27.5 27.5 19.8 No ductile1

160x80x5 13.0 28.9 18.9 Highly

200x100x5 16.9 36.4 20.5 Moderately

250x150x6.3 21.4 37.5 28.2 Moderately

-0.1 -0.06 -0.02 0.02 0.06 0.1-2

-1.6

-1.2

-0.8

-0.4

0

0.4

0.8

1.2

1.6

2

Backbone curves

Rotation [rad]

No

rmal

ized

mo

men

t

100x100x6.3

160x80x5

Results and discussions

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(ii) Moderately ductile members

Section b/t d/t L/r

Ductile

criteria

(AISC 341-

16)100x100x6.3 13.6 13.6 23.1 Highly

120x120x6.3 16.2 16.2 21.3 Moderately

150x150x5 27.5 27.5 19.8 No ductile1

160x80x5 13.0 28.9 18.9 Highly

200x100x5 16.9 36.4 20.5 Moderately

250x150x6.3 21.4 37.5 28.2 Moderately

-0.1 -0.06 -0.02 0.02 0.06 0.1-2

-1.6

-1.2

-0.8

-0.4

0

0.4

0.8

1.2

1.6

2

Backbone curves

Rotation [rad]

No

rmal

ized

mo

men

t

120x120x6.3

200x100x5

• Moment degradation is more evident with increasing values of b/t and d/t ratios,

especially for rectangular sections. This effect may be due to the interaction between

flange and web local buckling.

• 120x120x6.3 section was classified as moderately ductile member could be classified as

highly ductile members.

• 200x100x5 with similar b/t ratio did not behave as highly ductile members since higher d/t

ratio affected the rotation capacity.

Results and discussions

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(iii) Sections above and below the limit for

Moderately ductile members

Section b/t d/t L/r

Ductile

criteria

(AISC 341-

16)100x100x6.3 13.6 13.6 23.1 Highly

120x120x6.3 16.2 16.2 21.3 Moderately

150x150x5 27.5 27.5 19.8 No ductile1

160x80x5 13.0 28.9 18.9 Highly

200x100x5 16.9 36.4 20.5 Moderately

250x150x6.3 21.4 37.5 28.2 Moderately

-0.1 -0.06 -0.02 0.02 0.06 0.1-2

-1.6

-1.2

-0.8

-0.4

0

0.4

0.8

1.2

1.6

2

Backbone curves

Rotation [rad]

No

rmal

ized

mo

men

t

150x150x5

250x150x6.3

• Although, according to AISC classification, square section 150x150x5 cannot beeven used for seismic applications performed better than the rectangular section250x150x5 in terms of moment and rotation capacity.

Results and discussions

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The results suggest that relaxed limits for the width–to-thickness (b/t) and depth–to-thickness (d/t) ratios may be adopted for a more convenient use of hot-finished hollow steel sectionsin seismic bending applications , taking advantage of their improved ductility, result of hot-manufacturing process

+ DUCTILITY

+ STRENGTH/WEIGHT

+ ECONOMIC BENEFITS

Higher performance of steel frame for seismic

design usingHOT-FINISHED HOLLOW

STEEL SECTIONS

Concluding remarks