Design and Fabrication of
Suspension Bridge
Group 4: Cynthia, Gerald, Melanie, Brazy, Alberta
What is a Suspension Bridge?
• It gets its name from the fact that the deck/roadway is
suspended by vertical suspenders, which are connected to
supporting cables that run between towers and are anchored
in anchor blocks/anchorages at each end.
• Also, it is one of the most popular bridges as they are very
beautiful and elegant.
• They can easily cross distances between 610 and 2134
meters, this is an advantage over other bridge designs.
• However given the complexity of their design and the
materials needed to build them, they are very costly.
Tower
Anchorage
Supporting
cable
Suspenders
Deck
History of Suspension Bridges
• The earliest suspension bridges were made in the 15th century
by a man called Gylapo who used twisted yak skins as
suspension cables. This was so durable that one of them
survived until 2004 where it was destroyed by a massive flood.
• Later in 1532, twisted grass was used by the Incan Empire, and
spanned 45 meters across valleys. However they did not last
long and had to be replaced from time to time.
• The first modern-day suspension Bridge was done by Veranzio
in 1959, using timber and rope.
How does a Suspension Bridge
work?
• The suspenders transfer the load on the deck and the deck’s weight
to the towers via the supporting cables. This creates an arc of the
entire deck, and induces tensile forces in the anchorages, supporting
cables, and suspenders. Compressive forces are induced into the
towers, which carry most of the weight of the bridge.
• The anchorages are usually solid rock or massive concrete blocks
anchored underground and dissipate the forces deep into the ground
Our Initial design
Force resolution of Deck
𝑀𝑎𝑠𝑠 𝑜𝑓 𝐷𝑒𝑐𝑘 = 𝑉𝑜𝑙𝑢𝑚𝑒 × 𝐷𝑒𝑛𝑠𝑖𝑡𝑦
= 0.15𝑚 × 1𝑚 × 0.012𝑚 × 620 𝑘𝑔/𝑚3
= 1.116 𝑘𝑔
𝑊 = 𝐷𝑒𝑎𝑑 𝑙𝑜𝑎𝑑 + 𝐶𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑒𝑑 𝑙𝑜𝑎𝑑
= 11.16 𝑁 + 40 𝑁
= 51.16 𝑁
Ra = 25.58 N
W = 51.16 N
Rb = 25.58 N
Shear Force and Bending Moment
Diagram
𝑉/𝑁
25.58
0.5
0.2
𝑥/𝑚
0.8
- 25.58
76.4
𝑀/𝑁𝑚
𝑥/𝑚
0.2
0.5
0.8
Materials and Tools Used
• Plywood, 12mm thickness
• Woven Spiral Fiber, 2mm diameter
• Composite Wood, 1.5 cm thick
• Star-shaped Dowels
• Table saw, Hacksaw, Sand Paper, Ruler, Measuring Tape
Method of Fabrication
1.
2.
3.
4.
5.
6.
7.
8.
Cut deck and tower pieces
Drill holes into deck
Cut support-wedges
Smooth edges of wood with sand paper
Drill holes into towers and wedges
Assemble tower and support with wooden nails
Pass fiber through deck and towers
Tie suspenders to supporting cable
Finished product
Challenges Faced & Lessons
learned
• Making sure the ropes are taut
• Cutting wood against the grain instead of along the grain
• Fan blew one tower down from table
• Drilling straight
THANK
YOU