Lesson Plan 3: The Building of the Bridge Models
The objective of this lesson is for the students to each build their own individual bridges, using their drawings that have been inspired from nature and developed into feasible designs. Each student will have received a handout explaining the criteria for the building of their bridges at the beginning of the unit. This will give them time to thoughtfully develop their bridge designs as they are exposed to information throughout the unit. Students need to understand what is expected of them so that they can plan in advance. The handout will include size restrictions and bridge considerations. For example, the finished bridges may not exceed 36" in length, 8" in width and 24" in height because of room storage constraints. The actual building of the model will be a summation of all that they will have learned up to this point. This activity that entails the actual construction of their bridge models will be by far the longest activity in duration during this unit. It will take between two and three weeks and students will be encouraged to work on them during any free time that they have.
Students may choose the basic constructions of a beam bridge, an arch, a cantilever or a suspension bridge or any combination including the addition of trusses for support. It will be stressed that it is better to keep the concept and design simple. However, students must be able to explain the principles behind their design, exhibiting their understanding of how forces affect the strength of their bridge. Students should know if their bridges rely primarily on compression, tension or trusses to carry forces from the deck of the bridges to the bridges' supports.
The available materials in the classroom will be shown to the students with the strengths and weaknesses of some of the materials described. The safest, most sensible methods of cutting pieces will be demonstrated, including using mat board scraps under the pieces to be cut so that the table surfaces will be protected. Even though students will be working individually on their own bridges, they will be encouraged to brainstorm and share ideas, creating an environment of creativity and collegiality. Using the scaled drawings on graph paper that they have done during a previous lesson, they will make informed decisions on the appropriate materials to use for their bridge designs.
Materials will include mat board and foam board for the bridges and their bases. Scraps of these can be obtained free from most framing stores. Most frame stores usually have mat board scraps in quantity, but do not have as many foam board scraps on hand so you can call around and ask places to save them for you. Balsa wood is an excellent material for bridges. Clay can also be used. Most art teachers are scavengers and collect and save wire, string, drinking straws, wood, etc. X-acto knives, drills, a jigsaw and hand saw and pliers will also be available. Students can be creative and use a variety of materials and they can be encouraged to bring in their own materials if they desire. The bridge pieces can even be made out of rolled pieces of newspapers. It should be stressed, however, that the materials used should simulate the actual materials that would be used in their bridges if they were real. The students should try to use joints and connections similar to what their bridges would actually specify. The students will have a deadline for the completion of their bridges.
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