National Timber Bridge Design Competition - 2019

1. National Timber Bridge Design Competition - 2019 College or University Name: Lawrence Technological University Student Chapter (ASCE or FPS): ASCE Address: 21000 West Ten Mile Rd., Southfield, MI 48075 Website Address: www.ltu.edu Faculty Advisor: Mena Bebawy, PhD, P.E. Email: mbebawy@ltu.edu Phone: 248-204-2564 Student Member in Charge of Project: David Amegadoe Email: damegadoe@ltu.edu Phone: 248-204-2548

2. Hours Spent on This Project Students: 6 Hours/student (96 Hours/group) Faculty: 12 hours Cost of Materials Donated: None Purchased: Wood ($560) + Fasteners ($20) ≈ $580

3. Abstract (Maximum 500 Word Narrative): Explain the bridge design concept and what was done to optimize stiffness wile attempting to minimize weight of the structure. • The team aimed at creating a practical design that used the least amount of commercially available materials, while achieving the required stiffness. The team designed and built the bridge (including the deck) using #2 Prime Ground Contact Pressure-Treated Southern Yellow Pine with numbers and nominal dimensions as follows: • Thirty-two 2”×6”×12’ (for truss top/bottom chords, truss diagonals, deck, & gusset plates, $331.84) • Eight 4”×4”×12’ (for vertical truss members, bracing system, & top/bottom chord splices, $140.56) • Ten 2”×6”×8’ (for cross beams supporting the deck and transferring the load to two main trusses, $66.7) • Four 2”×4”×8’ (for curbs, $19.92) • The lumber was commercially available at a very reasonable price. Lengths and cuts of the wood were engineered to minimize the lumber waste to virtually none. Compatible Deckmate epoxy (polymer) coated deck screws # 9 × 3” were used as fasteners in the supporting truss system as well as the deck. Small size screws have the advantage over bolts or larger lag screws in distributing the load over a larger surface area and thus eliminating the stress concentration and the tear-out failure of wood. Besides, epoxy coating ensured durability of the fasteners. • The deck consisted of 2”× 6” boards continuously supported over five cross beams. Each cross beam consisted of two 2”×6” and was supported by two end trusses that served as guardrails for the bridge with a standard height from the top of the deck to the top of the truss (guardrail) of 42”. Deck boards were placed next to each other with a gap of 1/8” to allow for drainage and prevent water puddling on the bridge. • To enhance the lateral stability of the two main trusses, a bracing system was added to the outside of the truss and the cross beams extended to serve as a part of the bracing system. The bracing system provided a very efficient lateral system, while maintaining a clear roadway without overhead bracing. • The simple and efficient design facilitated the construction of the bridge and made it possible for the team put bridge together in approximately six hours. Besides, except for the wood screws, no material other than wood was used in the construction of the bridge.

4. 2. Deflection Table (Deflection – millimeters rounded to 2 decimal places) • Loading Increments • Bridge – As measured at midspan of the longitudinal beam receiving greatest loading. • Beam L – As measured under the longitudinal beam to left of selected deck monitoring point. • Beam R – As measured under the longitudinal beam to right of selected deck monitoring point. • Average (L & R) – Average of 3 and 4, above. • Gross Deck – As measured under the loading point expected to experience maximum deflection. • Net Deck – Column 6 minus Column 5. Deck Span: Transverse distance between main longitudinal bridge support members measured from inside edge to inside edge = _____835.03________mm ÷ 100 = _____8.35_______mm = maximum allowable net deck deflection.

5. 3. Materials List

6. 4. Summary – Describe Bridge and Its Behavior Under Load (max. 500 words) The bridge is composed of two main trusses serving as guardrails while supporting ten cross beams that support a 1.5-in.-thick deck. The trusses are simply supported at their ends and the deck is made continuous over the cross beams. The bridge was loaded using a hydraulic actuator, which applied the load through a wood spreader with four points of loading spaced according to competition rules. The clear deck span was 32.875 in. (835 mm) from the inside of the cross beam to the inside of the other cross beam. In the longitudinal direction, the load was applied at the mid-span as well as the mid-width of the bridge. Displacement was recorded using a data acquisition system, which also monitored the applied load. The bridge span from center to center of supports was 4000 mm. The maximum recorded deflection under the main truss at the end of the test was 8.59 mm, which was nearly equal to Span/465 Net deck deflection was under the span/100. The measured net deck deflection at the end of the test was approximately 7.35 mm, while the allowable deflection was 8.35 mm

7. Side Drawing (insert below)

8. End Drawing (insert below)

9. Trimetric Drawing (insert below)

10. Cross section under the point of maximum deck deflection. Section is taken at a distance of 11.75” (300 mm) from the mid-width of the bridge ( under a loading line) Drawing Clearly Showing Location of Loading and Deflection Gage Points in Relation to Longitudinal Members (insert below)NOTE: Repeat slide if loading set-up was moved to measure deck deflection.

11. Longitudinal section showing the main truss deflection gage in relation to the load Drawing Clearly Showing Location of Loading and Deflection Gage Points in Relation to Longitudinal Members (insert below)NOTE: Repeat slide if loading set-up was moved to measure deck deflection.

12. Drawing Clearly Showing Location of Loading and Deflection Gage Points in Relation to Transverse Members (insert below)NOTE: Repeat slide if loading set-up was moved to measure deck deflection.

13. PHOTO Showing SIDE View of Loading Setup for Measuring Bridge Deflection (insert below)NOTE: Repeat slide if loading set-up was moved to measure deck deflection. Location of three deflection gages for deck deflection Bridge deflection @ midspan under main truss

14. PHOTO Showing END View of Loading Setup for Measuring Bridge Deflection (insert below)NOTE: Repeat slide if loading set-up was moved to measure deck deflection.

15. End Photo of Finished Bridge

16. Side Photo of Finished Bridge

17. Trimetric Photo of Finished Bridge

18. Team Photo (with bridge in the foreground, where possible)

19. 6. Bridge Component Details

20. 7. Preservative Treatment: Describe the preservative treatment applied to 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. If treatment was not selected, explain why. Pressure treated ground-contact #2 Prime Southern Yellow Pine was used in the construction of all bridge components. In addition, the bridge will be water sealed annually to extend its lifespan Pressure treated wood is tested and recommended for exterior applications especially when the wood is expected to come into contact with soil or in areas with poor air circulation. Chemicals used currently in pressure treated lumber impose a little to no hazard on humans and the environment. Therefore, pressure treated lumber is safe and allowed for use in Michigan.

21. 8. Special Considerations –Indicate the End Use of Your Bridge Local businesses, parks, and golf courses showed interest in using the bridge. It has not been decided which agency will win the bridge but it is expected that the bridge will be donated to a facility with high traffic where people can see and appreciate the timber construction. In addition, annual maintenance of the bridge using appropriate water sealant will be indicated as a requirement of winning the bridge

22. 9. Summarize the Team’s Experience from Participation in this Competition. Was it beneficial? What steps would you recommend to improve the experience? • Team enjoyed working on the design, construction, and testing of the bridge. Teamwork with a drink and dinner made working on the bridge a fun experience.

23. Individual pieces as well as components of the bridge were weighed during the construction to estimate the total weight of the bridge Photo of Bridge Weighing

24. Beam right Beam left One photo of each deflection gauge at full loading, with identification sign indicating DECK, BEAM LEFT, BEAM RIGHT, BRIDGE. Load (lbs) Deck Bridge Load and deflection readings after holding for one hour (Load is in pounds and deflections is in inches)

25. Add as many photos as you wish showing the bridge construction process. Especially consider photos of internal structural components that may not be visible to judges from observing the finished bridge.

26. Add as many photos as you wish showing the bridge construction process. Especially consider photos of internal structural components that may not be visible to judges from observing the finished bridge.