Download
1 / 22
220 likes | 240 Views
Discover the structural concept and optimization strategy of a timber bridge designed by NJIT students. Learn about materials used, deflection analysis results, and the innovative construction techniques employed. 8
E N D
National Timber Bridge Design Competition - 2019 College or University Name: New Jersey Institute of Technology Student Chapter (ASCE or FPS): ASCE Address: Colton Hall, Suite 200 University Heights Newark, NJ 07102 Website Address: https://civil.njit.edu/ Faculty Advisor: Stephanie Santos Email: stephanie.ribeiro@njit.edu Phone: 973-596-2450 Student Member in Charge of Project: Krzysztof Buz Email: kkb27@njit.edu Phone:908-838-5801
Hours Spent on This Project Students: 135 Faculty: 15 Cost of Materials Donated: None Purchased: $975.13
Abstract (Maximum 500 Word Narrative): Explain the bridge design concept and what was done to optimize stiffness while attempting to minimize weight of the structure. To start out the design we analyzed a typical deck design. Therefore, our design is based on two main girders that consist of three 2x12s joined together with wood glue as well as screws. The reason why each girder consists of three 2x12s is because of the limitation on the overall member length. Since the overall length of an individual member cannot exceed 2 meters, we needed to add splices to the girders. Our bridge was designed to have an overall length of 3.96m. This meant that we would have to run at least two splices in each of the girders in order to meet the maximum length requirements. This presented a question of how to join and cut the wood. In order to stiffen up the girders, we decided to cut them at a 45 degree angle and join them with wood glue as well as two screws on each angled cut. We also staggered the cuts so that two cuts are not next to each other as well as changed the direction of the cut. To ensure that the two joined pieces of wood did not fall apart or cause more deflection, we utilized a 2x12 by 2 ft piece of wood on the side of the cuts as a gusset plate, and screwed them into the sides of the girders; effectively holding them together and preventing the cuts from shearing under load. The crossbeams were designed to be 2x10, spaced at about 14.5 in or 368.3 mm from each other. The deck was constructed from 3/4in plywood that was screwed into the 2x10 crossbeams. The curb was constructed simply with 2x4s.
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 = _________316.9____mm ÷ 100 = __________3.169__mm = maximum allowable net deck deflection.
4. Summary – Describe Bridge and Its Behavior Under Load (max. 500 words) Under load the bridge behaved as expected with some deflection at the center of the beam span. One of our worries was the deck defection however when it was loaded it behaved better than expected. The beam splices held as designed. However we did receive 7 mm of deflection which is 1 mm more then was predicted by RISA 2D which was the program used to analyze the structural behavior of the beams. As we applied more load the defection increased as expected. After all the load was applied the deflection of the bridge stayed the same with no more additional deflection being experienced. The deck and 2x10 set up worked great with the decking taking the 4 load points and spreading the load onto the 2x10s which then applied the load onto the beams.
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. Load points Deflection Meter
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.
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.
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. In order to preserve the timber bridge we will use Olympic Maximum stain and sealant. This stain and sealant should provide protection for up to 6 years. Seeing as we plan on displaying this bridge in front of our Civil Engineering building at NJIT it will be replaced next year by that years timber bridge therefore the 6 year protection should be sufficient for this purpose.
8. Special Considerations –Indicate the End Use of Your Bridge The plan for this bridge is to be displayed in front of our Civil Engineering building for a year until a new timber bridge is constructed. Displaying this bridge would show new students one of aspects of civil engineering as well as have students be interested in all these extracurricular projects.
9. Summarize the Team’s Experience from Participation in this Competition. Was it beneficial? What steps would you recommend to improve the experience? The experience that was gained from this project is the application of engineering concepts in real life. The problems that we had to overcome made us think outside of the box. During the design process we had the ability to use our knowledge from our classes to help us with analyzing the structural members. This project also gave us a practical application of some of the engineering programs that we are taught during our classes. The construction aspect of the project proved to be a valuable experience with solving problems very quickly as well technical skills required in wood working such as using saws and power tools. It was overall a fun experience that helps us to understand the fundamentals of civil engineering as well as how different materials behave under load and during construction.
One photo of each deflection gauge at full loading, with identification sign indicating DECK, BEAM LEFT, BEAM RIGHT, BRIDGE. Bridge
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.
