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)
	Cable-stayed bridges consist of one or more towers with many steel cables attached to various points on the tower and deck. Those cables are arranged parallel in a harp pattern, or all connect to the top of the tower in a fan design. Historically, cable-stayed bridges are used where the span length is between that of a cantilever bridge and a suspension bridge. Modern technological advancements in the field of structural engineering have given rise to the recent popularity of cable-stayed bridges across the world. Some of the major advantages of cable-stayed bridges are their elegant transparent appearance, increased stiffness over suspension-type bridges, efficient utilization of structural materials, and relatively small size of bridge elements. They offer the opportunity to cross large obstacles with elegance and economy, allowing great freedom of formal expression. Though most cable-stayed bridges are not made of structural wood, the design concepts are equally suitable for small structures, like the ones being designed for this competition. Our group collectively believed it would be advantageous in today's advancing civil engineering field to begin exploring the principles of design and construction of a cable-stayed bridge. Thus the motivation for designing one of the firstever cable-stayed bridges for the Timber Bridge Competition was born. Our objective was to build a wood bridge that is non-traditional, aesthetically pleasing, and structurally sound. Our bridge is composed of four 6X6 pressure treated select structural Douglas Fir columns supporting a bridge deck of 5 - 2X4 stringers, 45 - 2X4 decking pieces and 2 curbs. There are three transverse stringers comprised of two 2X6 members bolted together with 4X6 blocking at the ends. 2X4 bracing is provided as well as eight 1/4" diameter steel cables in a harp pattern tying into the deck are four 1/4" cables tying in horizontally to the columns to resist kicking out moments. This innovative design is the first of its kind in the competition. A challenge to design and to build, this bridge was constructed in just two months.

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)
	Our group decided to use LVDTs (Linear Variable Differential Transformers) to measure bridge deflection. These electromechanical transducers convert rectillinear motion of a caliper into a voltage potential. This allowed us to measure the output voltage of the LVDTs with multimeters. We opted for this measurement solution due to the possible risk involved with loading our bridge's cables with high tension. Per competition requirements, our bridge was subject to an increasing load for approximately 30 minutes and then a sustained 20 kN load for one hour. To generate the force a hydraulic jack and a wooden beam were secured so as to push against a ceiling beam inside the structural engineering laboratory our bridge was located in. A team member then sat on top of our bridge during loading to continuously increase the load as prescribed by the competition rules. Most of the delfection occurred during the initial increasing load. Once the maximum load was achieved and held constant for one hour, maximum bridge deflection increased very slightly.

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:	3 - Double 2x6 P.T.S.S.D.F. with 4 x 6 blocking
Deck:	45 - 2x4 P.T.D.F. No. 1
Floor Beams:	5 - 2x4 P.T.D.F. No. 1 (3m & 1m)
Suspension:	1/4 in stranded stainless steel cable
Unique:	cable-stayed bridge

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
	Our design is sustainable because we opted for wood that was available locally (harvested within 150 miles, bought within 15 miles). The wood was treated to AWPA standards with ACQ-B. This type of treatment was standardized by the AWPA in 1992 and is used for treating western wood species like Douglas Fir. The solution contains 66.7% copper oxide

7. Special Considerations
	and 33.3% quat as didecyldimethylammonium chloride. Our design is the first of its kind in the competition. We opted to design and build a cable-stayed bridge for its beauty, economy, and longevity. It was important for us to have a sustainable design that exercised supporting local businesses and reducing our impact on the environment. We plan to donate our bridge to our engineering department so that future students may become inspired to date to be innovative in engineering design and construction. Here are a few word from our team: Robert - "It truly was an experience worth having; all civil engineers should partake in a project like this. It was challenging at times, but together were able to complete our bridge that we are all very produ of." Hai - "This project has widened my knowledge about cable-stayed bridges and taught me the importance of teamwork." Candace - "Teamwork enabled us to get this project accomplished. Planning, communication and hard work are keys that facilitated the completion of our cable-stayed timber bridge."