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Description of Unit

This interdisciplinary unit includes math, science, technology, English language arts, and reading content. Additional ties could be made to drafting and architectural design. To engage fourth-grade students in the topic, the teacher will introduce relevant books—such as Iggy Peck, Architect by Andrea Beaty and Monsters Under Bridges by Rachel Roellke Coddington. Classroom discussion, video clips, or articles about architecture and bridge design will be shared to engage students, activate prior knowledge, and assist students in choosing a bridge type. Individually or in small groups, students will research various types of bridges, explore structural considerations, and design a bridge incorporating specific mathematical concepts. Using their designs, students will construct their bridge, present their research findings on the bridge type and model bridge to peers, hypothesize the architectural soundness of their bridge design prior to conducting a weight test using appropriate mediums, and have the opportunity to redesign and retest. Finally, students will give a presentation that includes information about their bridge design, construction and weight test, their weight test data, and approaches for the redesign and retest.

This guide links the Bridges unit to the Texas Essential Knowledge and Skills (TEKS) for fourth-grade students. Bridges is an interdisciplinary unit designed to foster an interest in STEM (science, technology, engineering, and math), the architectural process, and creative problem solving. In a world that depends heavily on the exchange of goods and transportation of people in the most efficient manner possible, bridges have become increasingly important to today’s society. According to the National Science Foundation:

In the 21st century, scientific and technological innovations have become increasingly important as we face the benefits and challenges of both globalization and a knowledge-based economy. To succeed in this new information-based and highly technological society, students need to develop their capabilities in STEM to levels much beyond what was considered acceptable in the past.

The following document includes the applicable TEKS and the details of the Bridges unit. The final section
of this document presents the applicable Texas College and Career Readiness Standards adopted by the
Texas Higher Education Coordinating Board (THECB) on January 24, 2008.

Phase I. Learning Experiences

  1. Students will develop deeper understanding of the various types of bridges, their purposes, and their construction. The teacher will share books—such as Iggy Peck, Architect by Andrea Beaty and Monsters Under Bridges by Rachel Roellke Coddington—video clips, and articles to engage the students and guide them through a discussion regarding the types, purposes, and construction of bridges. See the recommended websites in the Internet Resources section.

    Possible guiding questions for classroom discussion might include the following:

    • What do you know about bridges?
    • Why do we need bridges?
    • What defines a structure as a bridge?
    • What characteristics do bridges have?
    • Where might bridges be found or used?
    • What types of bridges are there?

    The teacher may also need to teach the students about the various types of bridges and preteach relevant vocabulary. This website is a resource for explaining different types of bridges including the following:

    • Arch bridge
    • Beam bridge
    • Truss bridge
    • Cantilever bridge
    • Tiered-arch bridge
    • Suspension bridge
    • Cable-stayed bridge
    • Pedestrian bridge

    The teacher will provide students with pictures of several bridges using Google Images or another search engine of choice, as well as those pictures included in Monsters Under Bridges, and have them identify the mathematical features in each. Possible concepts might include the following:

    • Angles
    • Lines
    • Line segments
    • Parallel and perpendicular lines
    • Lines of symmetry within a two-dimensional figure
    • Acute, right, and obtuse triangles

    During this time, the teacher can also lead a discussion about using a protractor to measure angles found in bridges and other aspects of bridges that can be measured. Depending on student understanding of these concepts, the teacher may need to provide additional instructional support of these math concepts.
    Possible questions for classroom discussion and to guide student research might include the following:

    • What do you know about bridges?
    • Why do we need bridges?
    • What shapes and angles are present in bridge design?
    • Is symmetry important in bridge construction? Why or why not?
    • What mathematical concepts are included in bridge design?
    • What role do angle measurements play in bridge design?
    • Depending on bridge type, are certain shapes favorable over others?
    • What is the optimal length of a bridge?
    • How do you determine how long to make a bridge?
  2. To develop understanding of the components of an effective weight test, students will be placed in small groups to conduct an experiment on how the length and strength of a bridge are related.

    • Two books of the same thickness
    • A small paper cup
    • Approximately 50 pennies
    • 4¼-inch-wide strips of paper with lengths of 5, 6, 8, 9, and 11 inches
    • Make paper bridges from the strips. For each strip, fold up 1 inch on each of the long sides.
    • Make a hypothesis about which bridge will hold the most pennies.
    • Start with the 5-inch bridge. Suspend the bridge between two surfaces with the two books holding down opposite ends. The bridge should overlap each book by about 1 inch. Place the paper cup in the center of the bridge.
    • Put pennies into the cup one at a time until the bridge collapses.
    • Record the number of pennies added to the cup. This number is the breaking weight of the bridge.
    • Repeat the experiment to find the breaking weights for the remaining lengths of bridges.
    • Predict the breaking weight of a 3-inch bridge and a 14-inch bridge. Explain your reasoning in your science journal.

    Have students consider the following questions:

    • What made this test effective?
    • Which variable was tested?
    • Was your hypothesis correct?
    • What are the characteristics of an effective weight test?

Phase II. Independent Research

A. Research process

  1. Selecting a topic. Students will choose a bridge type to research. Students will continue to develop their understanding and knowledge of bridges that were introduced in Phase I through further research using credible Internet sources, books, video clips, or other types of media.
  2. Guiding questions. The questions below may be used to guide students through their individual or small-group research.
    • How do you think the idea for fabricated bridges came about?
    • What purposes do bridges serve?
    • What factors influence what type of bridge is used in a particular region or location?
    • What materials are used in bridge construction?
    • Are all bridges made from the same materials? Why or why not?
    • Why would a bridge be made out of a specific set of materials?
    • What shapes are best for bridge strength?
    • What steps are needed to construct a bridge?
    • What types of careers are associated with bridge design and construction?
    • Would plate tectonics or other environmental factors affect the types, placement, or materials used in bridge construction for a specific location?
    • How has bridge construction changed over time?
    • Are there any instances where soil composition would factor into bridge construction? What considerations must be taken into account when determining the type of bridge needed in a specific location?
    • What happens when a bridge fails?
    • What can be done to improve a bridge if it fails?

    Students may generate their own questions in their science journal as well.

  3. Designing a research proposal. Students will develop a plan and construct a model bridge based on knowledge and information gained through their research. Students will determine the appropriate construction material for their bridge. They may utilize drafting and design programs, other technology resources, or paper and pencil. Their design needs to be drawn to scale and include specific information about their bridge, including the following:
    • Type of bridge
    • Materials needed
    • Types and measurements of angles and shapes found in their design
    • All dimensions needed to construct and replicate the design
    • Given name
  4. Conducting research. Students will construct a model of the designed bridge. Model bridges must meet these requirements:
    • Minimum of 10 pounds supported when tested
    • Minimum length of 12 inches
    • Maximum amount of 8 ounces of liquid glue
    • Maximum amount of one of the following:
      • 200 popsicle sticks (standard size)
      • 500 toothpicks
      • 300 cotton swabs

B. The product

Students will demonstrate what they have learned about bridges through the construction of a model bridge. The model will be constructed from a scaled drawing.

After presentations of the various bridges, students will individually generate hypotheses as to how much weight each bridge will support and which bridge type will support the most weight. They will record their hypotheses in their science journal.

Students will then conduct a weight test on their own bridge.

To test, weight (e.g., washers, books, bags of sugar, beans or weights) will be suspended from the center of the bridge using either bungee cords or rope and a standard five-gallon bucket. Students should take into consideration the weight of the bungee cords, rope, and bucket when calculating the amount of weight their bridge supports.

An integral part of the engineer design process is redesigning and retesting. Therefore, if the students’ bridge fails the test or the students wants to try and make their bridge stronger, they will be allowed to redesign and retest.

C. Communication

Communication will be done in two stages.

  1. Stage I: Throughout the scientific process, students will communicate to their peers the bridge type, purpose, mathematical concepts, and any additional information the students discovered while building the bridge. Students will then conduct a weight test on the bridge to support their hypothesis on the bridge’s strength and stability.
  2. Stage II: Students will conclude the project with a final presentation through an avenue of their choice. Possible means include posters, digital presentations, brochures, or oral presentations. The presentation will include an overview of their bridge design and construction, weight-test guidelines and data, and if applicable, approaches taken for the redesign and retest. The presentation audience may include outside guests, such as parents, school staff, or other professionals. The audience will be given time to ask impromptu questions to reflect student learning.

D. A completed project consists of:

  1. Research
  2. A design of a model bridge
  3. A constructed model bridge
  4. A research and design presentation
  5. A weight test and data collection
  6. A redesign and retest (if needed)
  7. A final presentation
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