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)
	The 2004 ASCE-OSU Chapter designed, constructed and tested a bridge to compete in the 2004 National Timber Bridge Competition. The team consisted of twenty (20) undergraduate students and one (1) graduate student who are active members of OSU-ASCE and are enrolled at The Ohio State University. The simply supported truss bridge has been designed to span four meters and safely carry 20 kN of load at any location on the deck surface with minimal deflection. This year’s bridge has been designed to make economical use of materials and labor. The economical design uses standard no. 2 pressure treated 2x southern pine lumber for all of the wooden components. This material has been selected because it is the most available material which meets the competition’s requirements for both durability and preservative treatment. The truss design was maximized using computer modeling and then modified to achieve an aesthetically well proportioned bridge. Extensive design is present in all of the truss member connections to prevent the possibility of sheer pullout. These connections consist of steel plates and bolts which are arranged to transfer tension forces from the member to four (4) strategically placed bolts to a steel plate to one (1) bolt and finally to two (2) gusset plates (one carpentry and steel fabrication on each side of the truss). Additionally, the bridge is a modular design made up of four (4) deck sections and two (2) truss sections which are completely independent of one another making it possible for the bridge to be assembled offsite and erected in difficult to access locations. This design is attractive because six (6) reasonably mobile bridge components can be brought on site and put together with minimal effort or expertise by merely sliding the deck panels into the steel buckets attached to the trusses and securely fastening the bolts that hold the components together. All fabrication, carpentry and steel work, was completed using The Ohio State University’s facilities by the student team members with the assistance of the Civil Engineering and Agricultural Engineering shop staffs. Nearly all of the bridge material was graciously donated for this project by local business.

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)
	As previously stated the bridge is a simply supported truss bridge. The two trusses span 4.1 meters and are 1.6 meters in height. The outer most and inner truss members are cut from standard 2x6 and 2x4 respectively. The truss members are pin connected to two 1/8 inch steel gussets plates at each node with ½” diameter stainless steel bolts. The end of each member that can conceivably experience tension has been reinforced with 1/8” steel plates connected to the respective member with four ¼” stainless steel bolts to allow the pin connection to be made relatively close to the end of the member. The deck is made up of 2x6 supported by a frame made of 2x8. The 2x8 frame is arranged to create twenty 1 meter x 0.25 meter bays. The deck frame is connected using standard 2x8 connected with galvanized joist hangers. The deck preformed well under the 20 kN load. Virtually no net deck deflection was realized. The overall deflection was 8.1 mm.

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:	2x8 no.2 pressure treated southern pine
Deck:	2x6 no.2 pressure treated southern pine
Floor Beams:	n/a
Suspension:	two truss made of 2x6 and 2x4 and 1/8" steel plates
Unique:	modular design

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
	Standard pressure treated lumber for above ground use, AWPA min. retention of 0.25 lbs/ft, CCA.

7. Special Considerations
	The team lacked having an active faculty advisor.