seismic performance of timber-steel hybrid structuresrisedr.tongji.edu.cn/ubc/ppt/5.5/plenary...

Zheng Li

PhD, Assistant Professor

Department of Structural Engineering

Tongji University

Seismic Performance of Timber-Steel

Hybrid Structures

The Fifth Tongji-UBC Symposium on Earthquake Engineering

"Facing Earthquake Challenges Together”

Outline

1. Introduction

2. Timber-steel hybrid structure

3. Experimental study

4. Numerical modeling

5. Reliability analysis

6. Summary

1. Introduction

Earthquakes!

1. Introduction

Christchurch earthquake, M6.3, New Zealand, 2011,

Photo by A. Trafford

Wenchuan earthquake, M8.0, China, 2008

Wenchuan earthquake, M8.0, China, 2008

Kobe earthquake, M6.9, Japan, 1995,

Photo by M.Yasumura

Murray Grove 8-storey CLT structure

in London (2008)

10-storey CLT structure

in Melbourne (2012)

Timber-concrete hybrid building in Quebec City

(2010)

Examples of multi-storey

timber buildings

1. Introduction

2. Formation of timber-steel hybrid structure

Why not hybridization?

Hybridization can be an alternative to develop multi-storey timber

buildings, because it normally combines the respective benefits of

different materials. In this project, a kind of multi-storey timber-

steel hybrid structure is proposed.

Timber-steel

hybrid structure

Timber hybrid diaphragm

Steel moment resisting frame

Suitable for multi-story buildings

Good seismic performance

Higher degree of industrialization

Advantages

Light wood-framed shear wall

Horizontal system

Vertical system

Steel frame

Infill wood-framed shear wall

Bolts

Anchor bolts

Hold-down

Timber-steel hybrid shear wall system

2. Formation of timber-steel hybrid structure

Specimen A :

light wood-framed diaphragm

single-sheathed infill wood-

framed shear wall

Specimen B:

Timber-steel hybrid diaphragm

double-sheathed infill wood-

framed shear wall

A-1, A-2, A-3 and B-1, B-2, B-3

are timber-steel hybrid shear

wall systems in specimen A and

specimen B.

3.1 Specimen design


Layout of specimen A and specimen B

Specimen A

(light wood-framed diaphragm &

single-sheathed infill wood shear wall)

Specimen B

(timber-steel hybrid diaphragm &

double-sheathed infill wood shear wall )


3.3 Installation of the specimen

The specimens were first subjected to non-destructive monotonic load to

study the initial lateral stiffness of the steel frame before and after the

installation of infills. Then fully reversed quasi-static cyclic load was

applied and cycled to 80% of degradation in the specimen’s strength.


3.4 Test Procedures

Nail heads embedding into

the sheathing panels

Failure of weld

• Failure modes


After the tests

Fatigue fracture of nails

Fall off of the

sheathing panels

(a) A-1 (c) A-3(b) A-2

• Hysteresis loops

(d) B-1 (f) B-3(e) B-2


• Share of force between timber and steel

In a timber-steel hybrid system, the lateral load was resisted by

the steel frame and the infill wood shear wall simultaneously. For

each specimen, the shear forces carried by the two subsystems

were obtained respectively. For instance, the shear force carried

by the steel frame and the infill wood shear wall of A-2 are shown

below.


• Share of force between timber and steelBased on the test results of the shear force carried by each subsystem, the

percentage shear force of each subsystem could be obtained.

• In the initial loading stage (within 25mm). The single- and double-sheathed infill wood

shear walls carried 50-75% and 65-95% of the lateral load of the hybrid system;

• When damages occurred in the wood shear walls, the percentage shear force in the

wood shear walls decreased, and the steel frame became more active.

Percentage shear force in the subsystems: (a) specimen with single-sheathed infill light wood-

framed shear walls; (b) specimen with double-sheathed infill light wood-framed shear walls


• Numerical model – timber-steel hybrid shear wall


• User defined element in ABAQUS


• Model validation


Load–displacement relationship

Energy dissipations

• Damage assessment


Test setup Backbone curves

Performance

level

Immediate occupancy

(IO)

Life safety

(LS)

Collapse prevention

(CP)

Drift limit (%) 0.7 2.5 5.0


Baseline walls: infill bf/ , 0.5,1.0, 2.5, 5.0rK k k


Earthquake input:

According to Chinese code of “Seismic design of building structures”, the

probabilities of 50-year exceedance for the earthquakes considered in the IO, LS,

and CP limit states are 63%, 10% and 2%, which are in accordance with the

average return period of 50, 475, and 2475 years.

NO. Event Date Station Component PGA (g)

1 Wenchuan 12/05/2008 Wolong EW 0.976

2 Tangshan 28/071976 Beijing Hotel EW 0.067

3 Ninghe 25/11/1976 Tianjin Hospital NS 0.149

4 Qian’an 31/08/1976 M0303 Qianan lanhe bridge NS 0.135

5 Chichi-1 21/09/1999 CHY006 NS 0.345

6 Chichi-2 21/09/1999 TCU070 EW 0.255

7 Chichi-3 21/09/1999 TCU106 NS 0.128

8 Chichi-4 21/09/1999 TAP052 NS 0.127

9 Kobe 17/01/1995 0 KJMA KJM000 0.821

10 Northridge-1 17/01/1994 0013 Beverly Hills - 14145 Mulhol MUL009 0.416

11 Northridge-2 17/01/1994 24278 Castaic - Old Ridge Route ORR090 0.568

12 Northridge-3 17/01/1994 90086 Buena Park - La Palma BPK090 0.139

13 Loma Prieta-1 18/10/1989 47381 Gilroy Array #3 G03000 0.555

14 Loma Prieta-2 18/10/1989 57425 Gilroy Array #7 GMR000 0.226

15 Loma Prieta-3 18/10/1989 58224 Oakland - Title & Trust TIB180 0.195


Hybrid shear wall with Kr=0.5 Hybrid shear wall with Kr=1.0

Hybrid shear wall with Kr=2.5 Hybrid shear wall with Kr=5.0

• Fragility analysis

• Response surface method


Step 1. Limit state function

( , , )a rG S K

Step 2. Response surface generation by numerical simulations

where Kr is a shear wall design factor

• 15 Spectrum levels (0.10, 0.16, 0.30, 0.45, 0.60, 0.75, 0.90, 1.05,

1.20, 1.35, 1.50, 1.65, 1.80, 2.05 and 2.10 g)

• 4 Kr levels (i.e. 0.5, 1.0, 2.5, and 5.0)

• 15 historical earthquake records


Step 3. Response surface fitting by polynomial functions

Step 4. Failure probability estimation

• Probabilistic-based design


Performance curves for the hybrid shear wall with Kr = 2.5

1. For the hybrid shear wall system, the infill wood-framed shear walls

were very effective in the initial stages of loading, while the steel

moment resisting frame turned out to be more active around the

ultimate limited state of the hybrid system.

2. Reliability analysis and performance-based seismic design of the

timber-steel hybrid building systems need robust computer models.

Moreover, the definition of the performance criteria and the

development of limit state functions are both key issues.

3. Different methods can be used in the evaluation of seismic reliability

of timber-steel hybrid systems, which offers effective tools for the

development of relative code provisions.

6. Summary

Thanks very much for your kind attention!

[email protected]

seismic performance of timber-steel hybrid structuresrisedr.tongji.edu.cn/ubc/ppt/5.5/plenary...

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