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| 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 overall concept was to employ laminated trusses with transverse decking to efficiently support the required loading with minimal deflections. The bridge was created to have a unique and aeshetically pleasing apperance while maximizing stiffness. Both the bridge and deck easily passed the deflection performance criteria. The truss design optimized stiffness and lowered the wieght of the bridge. Innovation was introduced in the design by creating the trusses from alternating layers of 3/4 inch treated plywood glue-laminated together. This enabled the truss to act as a frame structure and lower the deflection by eliminating deformations at member connections. The elimination of mechanical connections also aided in using less non-wood material. The support structure was made up of three of these trusses. The two outside trusses consisted of four alternating layers while the center truss had eight alternating layers. The transverse beams were made from pressure treated 2x4s and were used to minimize buckling and add stability. The decking for the bridge was constructed of three layers and the deck was analyzed and designed as a composite section. The bottom and middle layers were made up of 3/4 inch treated plywood placed transverse to one another and the wearsurface was constructed using pressure treated 2x12s. These layers were glued to one another and then screwed down. | ||
| 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) | ||
| The laminated-truss bridge was designed to be stiff and structurally efficient. When the bridge was loaded it performed better than the pre-deisgn analysis had predicted. After the initial load was applied there were some settling noises in the support structure. The allowable deflection at the midpoint of the bridge was 10mm and the intitial design analysis estimated 5.5mm of deflection. Under full load after the one hour load duration the bridge only deflected 4.49mm which is fifty-five percent less than the allowable deflection. The left truss deflections were slightly higher than the right truss which is expected to have been caused from craftsmanship of each of the trusses. This can possibly be eliminated by creating a precision jig to cut the pieces istead of cutting each piece out with a jigsaw and a "steady" hand. The deck also performed better than the design analysis. The deck was designed to have an allowable deflection of 5.56mm. The analysis predicted it would only deflect 2.25mm under load and it hoad an actual total net deflection of 1.72mm. This was a sixty-nine percent lower deflection than the allowadle. To check thrust displacement at the supports a mark was placed on the floor at all four corners of the bridge. While under full-load these marks were all able to be seen, showing there was virtually no horizontal movement. | ||
| 5. Project Drawings and Photos | ||||
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| 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: | Connectionless, glue-laminated trusses | Deck: | Three layers, two of plywood and one of 2x12s |
| Floor Beams: | 2x4 treated lumber with steel connector brackets | |
| Suspension: | ||
| Unique: | ||
| 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 | ||
| The wood for this project was commercially pressure treated for ground contact. The chemical used in the treatment was CCA-C with a 0.40 concentration. This preservative was selected for use due to the ease of purchasing the lumber from any local lumber supplier. | ||
| 7. Special Considerations | ||
| The bridge will be attached to a floating dock and used for a walkway from the embankment to the dock. The bridge will allow the owner to extend the dock further out into the water, while featuring an aesthetically pleasing structure. | ||
COPYRIGHT ©2009 - MSRCD
Programming by:Keith Mazer
All rights reserved.