The document describes the design and development of a modular pedestrian bridge made of composite materials. Key points: - The bridge is 18m wide and uses a modular assembly of identical spatial elements made of composites to reduce production costs. - Finite element analysis was used to dimension and optimize the structure. Modal analysis found vertical and lateral vibration frequencies above the required minimum. - A 1:1 scale physical model was made and used to create molds for vacuum bag laminating composite semi-modules. - Modules are joined with adhesive and external carbon fiber belts. Sensors will be used to map the bridge's tension state under different loads.

1. C o n v e r g e n z e p a r a l l e l e
l a b o r a t o r i d a l b a s s o
Lecce / Brindisi - Mesagne, 10 -11 luglio 2013
Progettazione e realizzazione di una passerella in compositi (CF)
Ricerca, sviluppo e progettazione interdisciplinare
Filippo Broggini arch.EPFL
BlueOffice Architecture, Bellinzona (Suisse)
C. TSCB, twin shape composed beam

2. TSCB - TWIN SHAPE COMPOSED BEAM
Filippo Broggini
BlueOffice Architecture (Bellinzona, Switzerland)
Architecture structural design
Luca Diviani
University of Applied Sciences of Southern Switzerland (Manno, Switzerland)
Study, design and material characterization
Study, develop and build a modular pedestrian bridge 18 m wide, characterized by a
fast assembly-disassembly system
mc2012 : Matérialités Contemporaines; Lyon 30.11.2012

3. 1.1 – THE IDEA
Context
When using composite materials,
smaller is the unit, lower are the
costs involved in the production of
the basic mold. Therefore, global
production costs can be reduced
by reducing the dimension of the
unit and optimizing the assembly
costs.
The basic idea is to produce a
monocoque shell starting from the
combination of identical spatial
elements.
The project aims at pushing the
product beyond its usual shape by
seeking new creative hints in the
morphogenetic shapes found in
diatoms, radiolars spatial elements.

4. 1.2 - DESIGN
Introduction
By observing micro-organisms like diatoms, the architect decomposes complex
shapes into spatial iterations and complex symmetries laying out simple elements
(modules) in space and generating more complex and expressive units.

5. 1.2 - DESIGN
Preliminary Concept
Initially the beam was thought just as a load-bearing element onto which some
plates made of pultrused products (walking zone), the fixed systems, the parapet
and the handrail were fixed.

6. 1.2 - DESIGN
Preliminary Concept
The construction of the first model
not only stimulated our plastic
research, but also increased our
confidence in the solidity of the
adopted shape.
Initially the beam was thought just as a load-bearing element onto which some
plates made of pultrused products (walking zone), the fixed systems, the parapet
and the handrail were fixed.

7. 1.2 - DESIGN
Final Concept
By actually handling the object, we gradually discover it, approaching more and
more closely the reality to build. So the idea of crossing the bridge going inside
the beam instead of on it gained footing.
By transforming the beam inside into
a transit zone and crossing in a real
spatial experience, we develop a
number of openings which
aesthetically lighten the beam, but
which also play the role of windows
on the surrounding territory

8. 1.2 - DESIGN
Scaled model of the foot-bridge
Also the internal aspects is strongly
relevant. Space is decomposed in
shadow and light zones, yielding a sort
of kaleidoscopic geometrization which
modifies its own aspect during daytime.
We have further improved body
geometry by setting up a new model
which is then produced exactly as in
reality, i.e. by means of a mold.

9. 2.1 – MATERIAL CHARACTERIZATION
Mechanical and Physical properties
The adhesion properties, with and
without ageing treatment, in order to
obtain the characteristics of the glue
best suited to composite-composite
and to composite-foam combinations.
• Laminates physical properties:
traction (ISO 527-1/4/5),
compression (ISO-14126), and
bending (ISO-14125).
Essentially, the fallowing test are carried on:
• Sandwich Flexural and Shear
Stiffness properties (ASTM
D 7250M, C 393M)

10. 2.1 – MATERIAL CHARACTERIZATION
Physical and durability properties
The specimens have been subjected
to artificial accelerated ageing by a
climatic chamber able to simulate the
weathering. The ageing was based on
the repeated exposure of the
specimens to the main weathering
agents, such as rain, temperature,
freeze/thaw cycles, humidity and
sunlight.
Durability properties, for the
verification of resistance to
atmospheric, environmental and UV
ageing.

11. 2.2 - DIMENSIONING
Finite Elements Model
Dimensioning, verification and structural optimization
was carried out by means of the Finite Element
(FEM) software Ansys 13.0
( TETTO:Top layout
core = 30 mm
Lateral layout
core = 20 mm
Bottom layout
core = 40 mm
Joint layout
L7
CC283
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s
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0.3
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L6
CC283
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L5
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90°
L4
CORE
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s
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30
mm
L3
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s
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L7
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L6
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45°
L5
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90°
L4
CORE
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s
=
20
mm
L3
CC283
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s
=
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90°
L2
CC283
;
s
=
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mm;
-­‐45°
L1
CC283
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s
=
0.3
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0°
L7
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;
s
=
0.3
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0°
L6
CC283
;
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=
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45°
L5
CC283
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=
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90°
L4
CORE
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;
s
=
40
mm
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=
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L2
CC283
;
s
=
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mm;
-­‐45°
L1
CC283
;
s
=
0.3
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0°
L12
CC283
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s
=
0.3
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0°
L11
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45°
L10
CC283
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=
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90°
L9
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=
0.3
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90°
L8
CC283
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s
=
0.3
mm;
-­‐45°
L7
CC283
;
s
=
0.3
mm;
0°
L6
CC283
;
s
=
0.3
mm;
0°
L5
CC283
;
s
=
0.3
mm;
45°
L4
CC283
;
s
=
0.3
mm;
90°
L3
CC283
;
s
=
0.3
mm;
90°
L2
CC283
;
s
=
0.3
mm;-­‐
45°
L1
CC283
;
s
=
0.3
mm;
0°

12. 2.2 - DIMENSIONING
Finite Elements Analysis – Static behavior
[mm]
The computed foot-bridge dimensions are: length 18.0 m; width 4.2 m and
height 2.4 m;
Boundary conditions were defined in a way to simulate the action of a
pedestrian 4.0 kN/m2 on the walkable surface; wind loads of 1.2 kN/m and
Snow load of 0.8 kN/m.
Analysis use loads
combination, based on SIA
(Swiss Society of
Engineers and Architects)
codes, which try to excite
the instability of the critical
elements.

13. 2.2 - DIMENSIONING
Modal and dynamic Simulations
The vertical vibration frequency is 8.6 Hz
and lateral vibration frequency is 6.2 Hz. it is
satisfied with the SIA design requirements
of 4.5 Hz as minimal frequency.
Tsai-Wu failure criteria was used to verify
the delamination of materials.

14. 2.4 - MANUFACTURING
1:1 scale model
The first step for the
mold construction is to
create a perfectly
designed reverse mold
of the final piece. To do
that, a 1:1 scale model
has been realized in
polyurethane material

15. 2.4 - MANUFACTURING
1:1 scale model
The first step for the mold
construction is to create a
perfectly designed
reverse mold of the final
piece. To do that, a 1:1
scale model has been
realized in polyurethane
material
After the milling phase,
the model has been
accurately painted and
polished

16. 2.4 - MANUFACTURING
Mold realization
The 1:1 polyurethane scale model has been use to obtain the reverse mold
in glass fiber material reinforced with a steel reticular structure.

17. 2.4 - MANUFACTURING
Mold realization
The 1:1 polyurethane scale model has been use to obtain the reverse mold
in glass fiber material reinforced with a steel reticular structure.

18. 2.4 - MANUFACTURING
Mold realization
All the semi-modules are been laminated using vacuum bag laminating
technique that uses atmospheric pressure as a clamp to hold laminate plies
together.

19. 2.4 - MANUFACTURING
Mold realization
After the lamination of the external skins and the assembly phase with internal
core material, the semi-modules was post-cured and finished.

20. 2.4 - MANUFACTURING
Mold realization
Two semi-models are glued together using an extremely high strength
structural adhesive. The complete module will be post-cured for 24 h.

21. 2.4 - MANUFACTURING
Assembly
Internally, Steel beams are used to align modules and to support axial loads.
Externally, modules are joined together by two bonding carbon fiber
layered belts, for inside and outside bonding area of the modules.

22. 2.4 - TESTING
Mapping tensional state
The foot-bridge will be put to real service equipped with sensors aimed at
mapping the tensional state in function of loads induced by different load
conditions, and allowing us to verify the static calculations and check the
manufacturing production quality.
This will be accomplished using electrical and optical fiber strain gages
and will allow, at the same time, to evaluate the peculiar features of these
different devices by comparing the results they deliver.
Fiber-optic sensors embedded within composite materials represent a new
branch of engineering with the potential to greatly enhance the confidence
and use of these materials.

23. 3.1 - CONCLUSIONS
“Ready to listen the material’s soul”
In the history of technologies and materials,
the first reaction of man is to apply the typical
shapes of old, known materials to the usage of
new ones.

24. 3.1 - CONCLUSIONS
“Ready to listen the material’s soul”
In the history of technologies and materials,
the first reaction of man is to apply the typical
shapes of old, known materials to the usage of
new ones.
Now the times are mature to face composite
materials through the logics pertaining to the
material itself.
It has to be left to future designers in next
years (but something is already happening
now) to interpret this challenge, which will
have to aim at creating not only new structural
and formal approaches, but also at conceiving
spaces resulting from the meeting of matter,
forces and fantasy.

25. © November 29, 2012
Filippo Broggini blueoffice.broggini@bluewin.ch
Luca Diviani luca.diviani@supsi.ch