In-Plane Testing of

Timber-Concrete Composite Floors

Students: Michael Newcombe & Wouter van Beerschoten

Supervisors: Dr. David Carradine, Assc. Prof. Stefano Pampanin

& Prof. Andy Buchanan

→ Post-tensioned frames and walls

→ Long spans

→ Thin concrete topping (TCC flooring)

→ Timber diaphragm connections

Potential for high floor flexibility…

New forms of multistorey timber buildings are evolving:

INTRODUCTION

(c.o. N. Perez)

BACKGROUND

Is floor flexibility a problem?

→ 1994 Northridge

- Several structures collapsed

- Higher diaphragm forces

- Higher drift demands on gravity systems

→ Lots of research on long span precast

concrete floors with concrete LLRS

(Fleischman, Lee and Kuchma, Miranda…)

→ Little investigation with solid timber LLRS

OBJECTIVES

Experimental:

Analysis:

1. Establish performance of

different diaphragm connections

2. Deformation components

3. Identify structural types that

may have a problem

4. Provide recommendations for

modeling

Dcon Dshear Dflexure

EXPERIMENTAL

Floor diaphragm:

Connectors

Instrumentation

Hydraulic Ram

Set up:

EXPERIMENTAL

Diaphragm Connections:

- Concrete-to-timber

Dowels (at 90°)

Screws

Inclined (at 45 °)

- Timber-to-timber:

Dowels (at 90°)

Screws

Inclined (at 45 °)

Nails Dowels (at 90°)

EXPERIMENTAL

Performance of Connections:

Conc.-Timber

Screws

90°

-15 -10 -5 0 5 10 15

Displacement (mm)

-40

-30

-20

-10

0

10

20

30

40

Force

(k

N)

EXPERIMENTAL

Conc.-Timber

Screws

45°

Performance of Connections:

-10 -5 0 5 10

Displacement (mm)

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

Force

(k

N)

EXPERIMENTAL

Performance of Connections:

Timber-Timber

Screws

90°

-15 -10 -5 0 5 10 15

Displacement (mm)

-50

-40

-30

-20

-10

0

10

20

30

40

50

Force

(k

N)

EXPERIMENTAL

Performance of Connections:

Timber-Timber

Nails

90°

-20 -15 -10 -5 0 5 10 15 20

Displacement (mm)

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

Force

(k

N)

EXPERIMENTAL

Performance of Connections:

Timber-Timber

Screws

45°

-20 -15 -10 -5 0 5 10 15 20

Displacement (mm)

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

60

Force

(k

N)

EXPERIMENTAL

Summary floor testing:

- Connection backbone curves vary

- Inclined fasteners are 4 times

stiffer than dowels

- Timber and concrete connections

with screws have the same stiffness

- Dcon >> Ddiaphragm

- Timber-to-timber connections:

→Easy construction and repair

→Less damage -15 -10 -5 0 5 10 15

Displacement (mm)

-7

-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

7

Fo

rce p

er f

ast

ener

(kN

)

Test 1

Test 2

Test 3

Test 4

Test 5

ANALYSIS

Q: For which structures do we need to model floor flexibility?

And to what complexity?

FRAMES

WALLS

Perform numerical analysis

(considering Kdiaphragm from testing)

Consider different floor geometries

Consider different LLRS

(single storey)

Consider different floor models

MDOF

SDOF 1

SDOF 2

0.90

0.95

1.00

1.05

1.10

1.15

1.20

1.25

1.30

1.35

1.40

0.00 0.04 0.08 0.12 0.16 0.20 0.24

Period, Tconn [s]

Dm

do

f / D

sd

of

0.90

0.95

1.00

1.05

1.10

0.00 0.04 0.08 0.12 0.16 0.20 0.24

Period, Tconn [s]

Dm

do

f / D

sd

of

ANALYSIS

Single storey results: Amplification of most flexible floor

FRAMES

Rigid Design limits

WALLS

0.70

1.20

1.70

2.20

2.70

3.20

0.00 0.04 0.08 0.12 0.16 0.20 0.24

Period, Tconn [s]

PF

A / P

GA

0.70

1.20

1.70

2.20

2.70

3.20

0.00 0.04 0.08 0.12 0.16 0.20 0.24

Period, Tconn [s]

PF

A / P

GA

ANALYSIS

Single storey results: Amplification of most flexible floor

FRAMES

Rigid Design limits

WALLS

ANALYSIS

Summary for single storey:

-For frame design:

Assume the diaphragms are rigid (within 2.5%)

- For wall design:

Model the diaphragm connections as a SDOF (within 5%)

ANALYSIS

Multistorey frames:

- Check the rigid diaphragm assumption

- Compare Rigid and SDOF floor

models

- What are the effects of higher

modes in the structure and

non-linear floor response

1/2500y:1/500y:1/50y:

ANALYSIS

Results for multistorey frames:

0.0

3.8

7.6

11.4

15.2

19.0

22.8

0.0% 1.0% 2.0% 3.0% 4.0% 5.0%

Drift

Heig

ht

[m]

0.0

3.8

7.6

11.4

15.2

19.0

22.8

0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75

PFAi / PGA

He

igh

t [m

]

Design

TargetFlexible

Rigid

Flexible

Rigid

Flexible

Rigid

ANALYSIS

Results for multistorey frames:

- Floor response spectra (since the floor diaphragm is a SDOF)

0

1

2

3

4

5

0 1 2 3 4 5

Period [s]

Ac

cle

rati

on

s [

g]

0

1

2

3

4

5

0 1 2 3 4 5

Period [s]

Ac

cle

rati

on

s [

g]

0

1

2

3

4

5

0 1 2 3 4 5

Period [s]

Ac

cle

rati

on

s [

g]

0

1

2

3

4

5

0 1 2 3 4 5

Period [s]

Ac

cle

rati

on

s [

g]

0

1

2

3

4

5

0 1 2 3 4 5

Period [s]

Ac

cle

rati

on

s [

g]

0

1

2

3

4

5

0 1 2 3 4 5

Period [s]

Ac

cle

rati

on

s [

g]

0

1

2

3

4

5

0 1 2 3 4 5

Period [s]

Ac

cle

rati

on

s [

g]

0

1

2

3

4

5

0 1 2 3 4 5

Period [s]

Ac

cle

rati

on

s [

g]

T1T2

T3

Tconn

ANALYSIS

Summary for multistorey frames:

- Rigid floor diaphragm assumptions is O.K.

- Inelasticity in the floor connections reduces the peak floor

accelerations

- The ground (design) spectrum can be used to determine the

peak floor accelerations

Tconn

PFA

T [s]Tconn

Acknowledgements

- Test rig: Anna Brignola and Stefano Pampanin