1. Design Brief
Liam and Dorsa

2. Introduction: Inquiry And Analysis
Material and Structure Limitations:
Maximum 75 popsicle sticks
Maximum 3 hot glue sticks
36cm minimum length
11 cm minimum width
≤20cm superstructure
≤20cm substructure
Design Challenge:
With a limited amount of materials, we must build a bridge that spans a gap of 30cm. Our success will be determined by the maximum amount of weight that can be applied to the bridge.

3. Term Definition Diagram Tension: Compression: Dead Load: Live Load:
Force that pulls an object, makes in longer
Compression:
Force that squeezes an object, makes it smaller/shorter
Dead Load:
Constant weight of the bridge itself; nothing except the raw materials
Live Load:
Temporary weight of objects on the bridge (snow, pedestrians, cars, trucks, etc.)
Racking:
Twisting and turning of a bridge, prevented with triangles and corner braces
Deflection:
The distance or angle that an object is moved when force is applied to it
42lbs
61lbs
Heavy

4. Possible Bridge Designs
Definition
Pros
Cons
Diagram
Suspension
Deck of the bridge is held up by vertical cables that are suspended from larger cables that run between towers above the deck
Easy to maintain
Inexpensive to construct
Can span very long distances
Strong wind can disrupt the bridge
It is a light bridge that cannot support loads as heavy as other bridge types
Cable Stayed
Deck of bridge is held up by cables running directly to the tower(s)
Sturdier than the suspension bridge
Quick construction time
Even less expensive than suspension bridges
Not as flexible as the suspension bridge
Can not span very long distances
Arch
Bridge is held up by curved substructure that redirects force into the ground at the bottom points of the arch
Gets stronger over time because of increased compression
Very limited span
Requires a large amount of time to construct compared to other bridge types
Beam
A single beam that spans the required distance
Easy to plan and construct
Inexpensive
Limited span, even less than the arch bridge
Cannot support very heavy loads
Truss
Superstructure composed of multiple triangles that distribute force equally around the entirety of the bridge
Lightweight
Can be constructed almost anywhere
Expensive to construct
Take up a lot of space for a relatively short spanning bridge
Possible Bridge Designs

5. Images of Notes Taken
Notes taken about different forces that affect bridges, along with different bridge types and the best materials.

6. Inquiry Questions What weight will our bridge break under?
What is the strongest bridge design?
Where is the strongest point to place the weight?
What are the strongest shapes and supports?
How will we divide the work equally?
Will we have enough materials to build the entire bridge?

7. Bridge Design Drawings
We came up with four possible bridge designs to build. There is a “Pros and Cons” list for each design that helped us to determine our final bridge product.

8. Bridge Design Drawings
1st Design: Double Truss
Height: 18cm
Length: 38cm
Width: 11cm
Pros:
Cons:
Forces are very much spread out
Takes up a lot of space
Multiple corner braces to strengthen sides
Heavy dead load
Sturdy shape due to large quantity of triangles
Majority of triangles are very large but unsupported
Very tall super structure makes the bridge unbalanced

9. Bridge Design Drawings
2nd Design: Arch Warren Truss
Height (Super structure): 9cm
Height (Sub structure): 11cm
Length: 35cm
Width: 11cm
Pros:
Cons:
Force is divided across both super and sub structures
Complicated design; difficult to construct
Multiple crosses in sub structure
Weak sides
Uses a lot of popsicle sticks; not many left to reinforce bridge
Heavy substructure may bend the bridge

10. Bridge Design Drawings
3rd Design: Homemade Design
Height: 10cm
Length: 36cm
Width: 12cm
Pros:
Cons:
Triangles have multiple braces
Weak joints in the centre
Force is split in half, then further divided
Little support on the side edges
Only two full triangle supports
Too many sticks used on the bottom

11. Bridge Design Drawings
4th Design: Truss (Chosen Design)
Height: 10cm
Length: 36cm
Width: 11cm
Pros:
Cons:
Multiple sturdy triangles
Lots of force being pushed to the bottom
Large braces to keep bridge intact
Weak joint in the centre*
Corner braces to reinforce sides
Lots of pressure on corner and centre braces
Short and balanced; dead load is well distributed
Lots of popsicle sticks left over to connect front and back faces
*weak centre joint

12. Chosen Design
We chose this design because we thought that it would distribute weight the best. One thing we overlooked in the other designs was the amount of popsicle sticks required to connect the front and back faces. This design does not need very many sticks for the faces, thus we can use a lot more for the connections. This bridge is not just random triangles stuck together. It has multiple braces that were carefully put into place to greatly strengthen the weak points.

13. Constructing The Bridge
Front face of the bridge being laid out

14. Constructing The Bridge
More preparation
Ready to glue

15. Constructing The Bridge
Front and back faces of the bridge
Crosses are used to attach the two faces

16. Constructing The Bridge
Bottom is complete

17. Constructing The Bridge
Top of the bridge is completed using crosses like the bottom
Braces are added to the sides so they can keep their shape

18. Bridge Is Finished!

19. Expectations
We hope that the bridge will be able to hold at least 65lbs
The sides have been reinforced, so they should hopefully stay in shape and no racking will occur
The bottom has to stay attached in order to keep the weight distributed

20. Work Distribution

21. Final Weight The final weight of our bridge was
90 pounds, exceeding our
expectations by 25 pounds.

22. Problem
Our bridge broke at two glue joints, one of which was not reinforced very well. However, no racking occurred, so the side and corner braces proved to be effective.