Paper Bridge Short Span 25 cm

Transcription

1 Paper Bridge Short Span 25 cm Name Teacher Period TAPE OF ANY KIND IS NOT ALLOWED. HOT GLUE IS NOT ALLOWED. Purpose - To construct a bridge from paper and glue that will support the heaviest load. The minimum supporting mass requirement is 5 pounds. Paper Bridge Record 565 pounds ATTENTION PARENTS AND STUDENTS The bridge project requires the fabrication of bridge components that may require the use of hand or power tools. Common tools used are scissors, knife, electric drill and handsaw or power saw. Follow all manufacturer safety guidelines and directions including the use of safety goggles. Tools should be used under adult supervision. The bridge project requires the fabrication of bridge components that may require the use of white glue. Follow all manufacturer safety guidelines and directions. Requirements 1. The bridge is to be constructed from white 8.5" X 11" or 8.5" X 14" computer/zerox paper and wood toothpicks. THERE ARE NO RESTRICTIONS ON THE USE OF THE TOOTHPICKS. NO OTHER PAPER PRODUCTS ARE ALLOWED. 2. ONLY Elmer's glue (generic white glue) or Elmer's glue stick (generic glue stick) are allowed. NOTE - White glue will not discolor or change the opaque characteristic of the paper. Any white glue or glue stick that discolors the paper is NOT allowed. Allowed Glues 3. Tape of ANY type is NOT allowed. Hot glue is NOT allowed. 4. The MASS of the bridge shall not exceed 200 GRAMS. MASS OF BRIDGE < 200 GRAMS (MASS IS LESS THAN OR EQUAL TO 200 GRAMS)

2 5. The bridge shall be freestanding and must SPAN two level surfaces that are 25 centimeters apart. It is recommended that the minimum length of the bridge be no less than cm (11 inches). LENGTH OF BRIDGE > 25 CM (SUGGESTED MINIMUM LENGTH IS CM OR 11 INCHES) 6. The bridge MUST incorporate a truss design. Students should research truss designs or DESIGN THEIR OWN unique truss design. If a student selects to design his or her own unique truss design, it is recommended that his/her teacher review the design. THE TRUSS MUST PROVIDE THE BRIDGE S STRUCTURAL STRENGTH. 7. NO inverted bridges (trusses are beneath the roadway). 8. All students are REQUIRED to use the bridge design simulation. Bridge Design Simulation The support for the bridge shall be from the top of the level surface. The edges of the level surface cannot be used in any way for support. ACCEPTABLE (table provides only vertical support) UNACCEPTABLE (table is providing horizontal support)

3 10. You must incorporate a "loading zone" at the midpoint of the span along the centerline of the bridge. The loading zone must receive a 5-cm x 10-cm flat block of wood called the loading platform. A halfinch hole must be located at the center of the loading zone and pass completely through the deck and all bridge supports beneath the deck. A bolt will be inserted through the hole from beneath the deck and attached to the loading platform. Your instructor will provide the bolt and loading platform. ½ hole Actual Loading Platform (teacher will provide) Loading Zone The purpose of these pictures is to aid in the explanation of the bridge project requirements. These pictures are NOT intended to be examples of quality construction or design. LOADING ZONE WILL THE BLOCK FIT?

4 11. The bridge must include a decking of paper to provide a suitable road surface at least 5-cm wide across the full span of the bridge. Four conditions must be met: - The deck may not have any gaps. - A block of wood 5-cm x 10-cm x 1-cm representing a car must be able to move along the length of the deck unobstructed from end to end. - The highest point of the deck may be no higher than 5 cm above the tabletop to allow for loading zone reinforcement. - The deck of the bridge must either be flat across its entire span or inclined upwards towards the loading zone. 12. The bridge may NOT be COLORED in any fashion (paints, canyons, markers, etc.). The color of the bridge must reflect the color of the paper and glue used. 13. Failure to meet these specifications will result in grade penalties. See grading rubric for details. Bridge Testing 1. A load (force) will be applied to the loading zone. 2. The load will be increased until structural failure is reached. 3. Structural failure is defined as: a member fails: tears or buckles, a joint fails: breaks or pulls out, the loading platform pulls through the loading zone, the roadway deflects vertically 2 inches, or the bridge is pulled through the 25 centimeter gap. 4. The greatest load applied without partial or complete structural failure will determine the final grade. Refer to the bridge rubric for details. 5. Students can not benefit from accidental grade rubric omissions or mistakes. Omissions and mistakes will be corrected and bridges will be evaluated appropriately.

5 Key to Member Construction Member construction should demand considerable attention. Although researching member construction is an excellent idea, that alone is not enough. One should experiment with various sized and shaped members before deciding on the best design for that person. Due to differing mechanical skills, a member design that is great for one student may be difficult for another. Bridges that take compression and tension into consideration and build the appropriately sized and shaped members are superior to bridges with uniformly constructed members. What will work best for you? Experiment and find out! Basic Member Construction 1. Roll a piece of paper into a tube with a diameter roughly the size of a quarter. 2. Carefully place the tube on the tabletop making sure the tube doesn t unravel. 3. With both hands flat and palms facing down, position the tube along the middle of your fingers. 4. Roll the tube away from yourself while applying a gentle downward force on the tube. 5. Reposition the tube and your hands once the tube has rolled to the bottom of your palms. 6. Repeat until the tube has tightened up to the desired size. 7. Securely the tube from unraveling with glue.

6 Key to Joint Construction Since most bridges will fail at the joints, joint construction should demand maximum attention. Although researching joint construction is an excellent idea, that alone is not enough. One should experiment with various joining techniques before deciding on the best technique for that person. Due to differing mechanical skills, a joining technique that is great for one student may be difficult for another. Excessive use of glue is not the key to building a robust joint. Glue should be used sparingly. Joints that are mitered and fit flush along with reinforcement techniques have proven to be superior to poorly engineered joints reinforced with excessive amounts of glue. Reinforcement techniques may include but are not limited to the following: pinning, slotted connections or gusset plating. What will work best for you? Experiment and find out! Basic Joint Construction Colored paper has been used to show the joints. You may NOT use colored paper. 1. Butt two members of approximately the same size together end-on. 2. Wrap a piece of paper around the two members, centered on the butted ends. 3. Repeat steps 3 through 7 of Basic Member Construction. Click here for larger images.

7 Key to Loading Zone Construction Finally, consider reinforcing the loading zone. A poorly designed and reinforced loading zone may result in structural failure ONLY at the loading zone. This unfortunate over site may leave the rest of the bridge structurally intact. Loading zone reinforcement should not be limited to excess use of glue but may include the construction of additional members (i.e. layers and/or joint construction). Remember the entire weight supported by the bridge is applied at the loading zone. What will work best for you? Experiment and find out! Loading Platform 5 cm X 10 cm X 1 cm (teacher will provide) Complete bridge breaking set-up. You may NOT use colored paper. Bridge Design Worksheet Template and Force Analysis

8 GREEN ZONE Acceptable Bridge Paper Bridge Grading Rubric - Violations ORANGE ZONE Acceptable bridges with MINOR infractions RED ZONE Unacceptable bridges with MAJOR infractions Bridge meets all design requirements Bridge will be tested until structural failure is reached and scored* between 65 and 100. A bridge that receives a failing grade may raise their grade by entering a bridge on the make up day. See orange zone for explanation. Bridge exceeds maximum mass limit by no more than 50 grams Bridge fails to include a proper loading zone. A bridge with one or more of the above infractions will be tested until structural failure is reached and scored* between 60 and 80. A bridge that receives a failing grade may raise their grade by entering a bridge on the make up day. See orange zone for explanation. If a bridge has both an orange zone and a red zone infraction, it will be evaluated according to the red zone infraction. Bridge exceeds maximum mass limit by more than 50 grams Bridge fails to incorporate a properly design loading zone or truss design Bridge fails minimum length requirement Bridge is constructed with disallowed material(s) A bridge with one or more of the above infractions will be tested if structurally possible until structural failure is reached and scored between a 50 and 70. A bridge that can not be tested will receive a grade of zero. Students may raise their grade by entering a bridge meeting all design requirements on the make up day. The make up bridge will be tested until structural failure is reached and scored between 60 and 80. Make up bridges will follow the orange zone rubric. A make up bridge that fails to meet ALL design requirements will not be evaluated. * A bridge that meets the minimum supporting mass requirement will receive a passing grade.

9 Paper Bridge Grading Rubric Scoring Score Green Zone Orange Zone Red Zone 100 A bridge that supports a weight equal to 200 lbs. earns a Bridges that support more than the minimum but less than 200 lbs. will be scaled between and 80. A bridge that supports just the minimum earns an 80. Make up bridges will be scored according to the orange zone rubric below. A bridge that supports a weight equal to or greater than 200 lbs. earns an 80. Bridges that support more than the minimum but less than 200 lbs. will be scaled between 79 and A bridge that supports just the minimum earns a A bridge that supports a mass greater than the 1 lb. but less than the minimum earns a 65. A bridge that supports a mass greater than the 1 lb. but less than the minimum earns a 60. A bridge that supports a weight equal to or greater than 200 lbs. kg earns a 70. Bridges that support more than the minimum but less than 200 lbs. will be scaled between 69 and 60. A bridge that supports just the minimum earns a A bridge that collapses under its own weight earns a zero. A bridge that collapses under its own weight earns a zero. A bridge that supports a mass greater than the 1 lb. but less than the minimum earns a 50. A bridge that collapses under its own weight earns a zero.

10 Paper Bridge Scoring Scale Weight Applied Scoring Zone Green Zone Orange Zone Red Zone 200 pounds pounds pounds pounds pounds pounds pounds pounds pounds pounds pounds pounds pounds pounds pounds pounds pounds pounds pounds pounds Weight = Minimum (5 lbs.) lb. Weight < Minimum Bonus Points One bonus point will be awarded for every 20 lbs. in excess of 200 lbs. Bonus points are awarded ONLY to green zone bridges. Red and orange zone bridges are ineligible for bonus points. Late Grade 10 points will be deducted for each day late.

11 Paper Bridge Score Card Name Name Teacher Period On-Level Mass of Bridge (grams) Weight Supported (lbs.) Score PreAP Mass of Bridge (grams) Efficiency Factor (See Bridge Scoring Spreadsheet) Weight Supported (lbs.) Scoring Weight (See Bridge Scoring Spreadsheet) (lbs.) Score Bridge Check List Criteria Green Zone Orange Zone Red Zone Mass m 200 grams 200 g < m 250 g m > 250 g Length > 25 cm > 25 cm < 25 cm Width 5 cm < 5 cm Loading Zone Fits correctly. Fits incorrectly Does not fit. Materials Permitted Permitted Disallowed Competition Color GREEN ORANGE RED Bridge Testing Questions 1. Draw a stick drawing of your bridge on the grid to the right. 2. On your stick drawing, identify where you predict structural failure occurred. 3. Place a large red X on your bridge where you predict structural failure will occur. 4. Did the structural failure occur where predicted? YES NO 5. Why did the structural failure occur where it did? Was it a design or construction oversight? Explain. Answer on the backside or a separate sheet of paper. 6. How would you improve your design? Answer on the backside or a separate sheet of paper.

12 Paper Bridge Second Bridge? Name Teacher Period

13 Bridge Short Span Pre-Build Questions Name Teacher Period Go to for bridge directions and course calendar to answer the questions below. 1. What type and size paper is allowed in the construction of your bridge? 2. What type of glue is allowed in the construction of your bridge? 3. What types of glue are NOT allowed in the construction of your bridge? 4. Is tape allowed in the construction of your bridge? 5. What are the bridge s mass and length requirements? 6. What is the width of the opening your bridge must span? 7. Should you build your bridge longer, shorter or the same length as the width of the opening? 8. Define truss. 9. Draw a sketch of a simple truss. 10. How must your bridge be supported?

14 11. Describe the size and location of the loading zone. 12. What is the size of the loading platform? 13. How much of the applied breaking force is applied to the loading platform/loading zone? How should the construction of your bridge take this into consideration? 14. What is the minimum width of the roadway? 15. May you decorated or color your bridge? 16. What defines structural failure? 17. How much weight must your bridge support for a passing grade? 18. What grade do you want to earn on this project? How much weight must your bridge support to earn this grade? 19. When is the bridge due? When will testing of the bridges begin? 20. What will happen to your bridge after testing?

15 Bridge TEKS/Objectives Introduction TEKS (1) Physics. In Physics, students conduct laboratory and field investigations, use scientific methods during investigations, and make informed decisions using critical thinking and scientific problem solving. Students study a variety of topics that include: laws of motion; changes within physical systems and conservation of energy and momentum; forces; thermodynamics; characteristics and behavior of waves; and atomic, nuclear, and quantum physics. Students who successfully complete Physics will acquire factual knowledge within a conceptual framework, practice experimental design and interpretation, work collaboratively with colleagues, and develop critical thinking skills. Knowledge and Skills TEKS (1) Scientific processes. The student conducts investigations, for at least 40% of instructional time, using safe, environmentally appropriate, and ethical practices. These investigations must involve actively obtaining and analyzing data with physical equipment, but may also involve experimentation in a simulated environment as well as field observations that extend beyond the classroom. The student is expected to: (A) demonstrate safe practices during laboratory and field investigations; and (B) demonstrate an understanding of the use and conservation of resources and the proper disposal or recycling of materials. (2) Scientific processes. The student uses a systematic approach to answer scientific laboratory and field investigative questions. The student is expected to: (E) design and implement investigative procedures, including making observations, asking well-defined questions, formulating testable hypotheses, identifying variables, selecting appropriate equipment and technology, and evaluating numerical answers for reasonableness; (K) communicate valid conclusions supported by the data through various methods such as lab reports, labeled drawings, graphic organizers, journals, summaries, oral reports, and technology-based reports; and (3) Scientific processes. The student uses critical thinking, scientific reasoning, and problem solving to make informed decisions within and outside the classroom. The student is expected to (A) in all fields of science, analyze, evaluate, and critique scientific explanations by using empirical evidence, logical reasoning, and experimental and observational testing, including examining all sides of scientific evidence of those scientific explanations, so as to encourage critical thinking by the student; (E) research and describe the connections between physics and future careers; and (F) express and interpret relationships symbolically in accordance with accepted theories to make predictions and solve problems mathematically, including problems requiring proportional reasoning and graphical vector addition. (4) Science concepts. The student knows and applies the laws governing motion in a variety of situations. The student is expected to: (D) calculate the effect of forces on objects, including the law of inertia, the relationship between force and acceleration, and the nature of force pairs between objects; (E) develop and interpret free-body force diagrams; and