National Timber Bridge Design Entry

College & Team Information
College or University:		Student Chapter:
Address:
Phone:	Fax:	E-mail:
Website address:		Faculty Advisor:
Person In Charge of Project:

Team Member	Class	Team Member	Class










Hours spent on project:		Cost of Material ($ Amount)
Student:	Faculty:	Donated:	Purchased:

1. Abstract - (Max 500 word narrative)
	For our bridge design, we decided to use new technological advancements to enhance the unique design of our structure. Our team is utilizing new materials that have not been placed in the NDS wood code. For our decking, we decided to use Skidguard plywood panels because Skidguard panels are waterproof and slip resistant. Skidguard plywood are especially designed for the usage for boat decks. For our top chord, we used Douglas Fir wood purchased from Home Depot. The Douglas Fir wood has a measurement of 2x6 on both sides. Then we used 2x6 Douglas Fir joist members to connect the two sides together to form the deck understructure. In order to make the joist hangers secure properly and tightly to the top chord, we used Simpson 2x6 face mount hangars for joist and we also added epoxy filler. This epoxy is used to fill the gaps between the top chord and the joist members. A significant advantage of this epoxy filler is that it is easily hand mixed and in 20 minutes it will be as strong as steel. This in turn will optimize stiffness by stopping deflection at the joints, without increasing weight to the structure. For our truss design, instead of using steel, which would add tremendously to the weight of the structure, we decided to use the Brazillian wood called Ipe. This wood has not yet been tested in depth to be placed in the NDS wood code. However, we decided to use this wood because it has not been used before and it has a lot of advantages. The advantages of ipe include: it is naturally resistant to rot and decay, and it is twice as dense as other wood species, up to five times harder. In addition, ipe possesses a beautiful dark brown colour. Another component that we used was carbon fiber, formerly an exotic material used in structural components of military planes and stealth bombers in the 80s and 90s. We mixed the carbon fiber with epoxy resin glue to the truss connections and the bottom portion of the T-beam. This is very effective

2. Deflection Table
Deflection (millimeters - rounded to 2 decimal places)
Loading Inc.	Bridge	Beam L	Beam R	Average (L&R)	Gross Deck	Net Deck
5 kN
10 kN
15 kN
20 kN - 0 min.
20 kN - 15 min.
20 kN - 30 min.
20 kN - 45 min.
20 kN - 60 min.
1) Loading Increments.
2) Bridge - As measured at midspan of the longitudinal beam receiving greatest loading.
3) Beam L - As measured under the longitudinal beam to left of selected deck monitoring point.
4) Beam R - As measured under the longitudinal beam to right of selected deck monitoring point.
5) Average (L&R) - Average of 3 and 4.
6) Gross Deck - As measured under the loading point expected to experience maximum deflection.
7) Net Deck - Column 6 minus column 5.
Deck span (transverse distance between main longitudinal bridge support members measured from inside edge to inside edge) = mm / 100 = mm (max. allowable net deck deflection)

3. Materials List
Material Item	Weight (kg)




















Total Weight (Kg)
Weight Non-wood (Kg)
Percent Non-wood

4. Summary -Describe Bridge and behavior under load - (Max 500 words)
	An innovative idea used on this bridge to improve its load capacity, reduce deflection, and reduce weight, was to use carbon fiber and epoxy to reinforce the side beams, joints, and trusses. Carbon fiber is strong in tension, so it was used on the underside of the beams and joints. The bridge showed very little deflection even under a (20kN) 5000 lb load. Epoxy matrixed carbon fiber used on the bridge is extremely brittle but have an extremely high tensile modulus and tensile strength. The tension modulus of carbon fiber is nearly ten times that of wood. This is the reason why we were able to see an incredibly small deflection. Since fibers can only pull and not push, it is only applicable for use under tension. When we reinforced the bottom side of the longitudinal beams, the carbon fiber would be in pure tension when the bridge is under load, which in essense acts as still rebars used in concrete. The bridge in theory, will fail slowly with the epoxy shearing off the wood it bonded to and the carbon fiber breaks plastically once the stress on it reaches its tensile strength. However, only a miniscule of epoxy cracked and the carbon fiber was unbroken under a (20kN) 5000 lb load.

5. Project Drawings and Photos

Longitudinal Cross Section	Tranverse Cross Section	Trimetric View	Project Photo	Team Photo
Click on drawing or photo above for larger view.

6. Component Details
In ten (10) words or less per each component below, describe the bridge:
Stringers/Girders:	Douglas Fir is exceptionally versatile with high strength.
Deck:	Skidguard panels are waterproof and slip resistant.
Floor Beams:
Suspension:
Unique:	Expoxy is as strong as steel minus the weight. Ipe is naturally resistant to rot and decay. Carbon fiber pushes back the compression of the applied loads.

Describe preservative treatment for all wood members. Include type and concentrations. Also include a short statement of why this treatment was selected. Did the treatment requirement present any special problems? If yes, provide details
	We chose to purchase wood that was pretreated at Home Depot. Although pretreated wood is more expensive, we believe that it will be more thoroughly pretreated and more effective. The Skidguard plywood produced by Simpson Olympic Panel is also pretreated so that it is waterproof and more durable.

7. Special Considerations