Strategies
Most art teachers have always used differentiated instruction, even before it had this catchy label. Since I have a wide variety of students who range from the valedictorian at one end to special education and REACH students at the other, I use a variety of strategies and activities for maximum learning. REACH students are those who have exceptional needs beyond those of the mainstreamed special education students. There are certain concepts that all of the students are expected to understand. For example, the forces of compression and tension are two ideas that are integral to the understanding of bridges. It could be on a level of "push" and "pull" which explains compression and tension on their simplest levels or it could be on a much more in-depth level of understanding. For example, I may have AP Physics students and students in AP math classes. Their understandings of the math formulas and the applied technology involved may far exceed mine. They can extend these understandings to further levels (taking these ideas and "running with them") for extra credit and personal satisfaction, if desired. All students can be successful with this unit and all students can be successful building bridges. The different levels of understanding and sophistication are normal and do not detract from the final results.
As an introduction to bridges, I will start with a CRISS (Creating Independence through Student-owned Strategies) Strategy called "Think-Pair-Share." If your classes are larger like some of mine, instead of pairing the students, the students can work in small groups. Large hands-on art classes present multiple challenges so teaching methods can be adapted and supplies stretched or substituted and space utilized as best as possible. Also, I teach in an AB Block schedule setting with 90 minute classes. For our art classes, that is a vast improvement over our previous model that featured 45 minute classes. All of the strategies and activities in this unit can be adapted to any scheduling model. In this beginning activity, each student will individually write down possible purposes of bridges and then share these in small groups at their tables. Then each group will share and discuss these with the whole class. This will hopefully serve as a stimulating "jumping off point" for the rest of our unit. The resulting discussions and sharing of ideas are essential parts of the learning for this unit. The students will list the results from this activity on an 18" x 24" piece of paper that will be hung on our "Bridge Wall." During the unit, we (the students, not just I) can add anything deemed relevant to the wall for sharing and future reference. Further explanation about the display wall appears later.
This "Think-Pair-Share" strategy can also be used as a short student-centered activity to stimulate any introductory thinking for the next part of the unit. It can be used to stimulate student thinking about actual bridges by naming real bridges such as the Delaware Memorial Bridge (a major suspension bridge on which most of my students have traveled) or the small overpass down the road from our high school (a beam bridge). They will also name types of bridges in a separate activity. Even though these introductory activities are separate, their findings are interrelated. Each bridge that they name also represents a basic type or combination of bridge types. The key to the "Think-Pair-Share" strategy is to adhere to the time limits to keep it short and the students focused.
Many of my students are visual learners. To ensure understanding, I want to use visual representations of the various concepts involved. I can show compression with a very simple but effective demonstration by compressing (pushing or pressing) my palms on either side of a row of approximately 10 books. By compressing the sides of the books, the whole row of books can be picked up. I will draw a simple sketch of a row of books embraced by hands on the board with arrows pointing inward from the sides, labeling them with the words "compression." (See Figure 1.). For visual learners who may be reading this, please refer to the appendix for sketches of these activities. Of course, all types of learners may benefit from viewing these.
To further reinforce the idea of compression, foot-long lengths of a swimming pool noodle can be distributed and shared. Any similar flexible material can be substituted. The students can actually see for themselves the wrinkling or compression of the Styrofoam-type material on the inside of the curve when the length is bent. This demonstration also introduces the force of tension. While the material on the inside of the curve is compressed, conversely, the bottom of the curve is stretched out and is then in tension. (See Figure 2.). Even a single uniform piece of computer paper (or just about any paper, for that matter) will display the properties of compression and tension. When the sheet is in tension (pulled on), it exhibits so much more strength than when it is in compression (the ends are pushed together and it immediately buckles and crumples, rendering it useless unless you are a scavenger like me who saves practically everything). (See Figure 3.). These demonstrations lead the learners into understanding the concepts of tension and compression. These forces can also be demonstrated with the simple bending of other materials such as a ruler, pencil, yarn, wire, a brick, etc. Some are weak when in tension while others are weak in compression. (2) A typical ruler laid flat and supported at each end will bend fairly easily when a force is applied at its center. However, when the same ruler is turned on its edge, it will resist the same force with very little bending at the center. The amount of available material is the same in both positions. (See Figure 4.) (2) However, this example illustrates the strength and concept of a girder as derived by the geometric properties of the cross section in their respective positions. This can also lead naturally into the use of materials and environmental factors. To illustrate the strength of a properly and improperly mixed material like concrete, plaster can be substituted for the cement portion. Students can mix a predetermined amount of dry plaster in a paper cup with varying amounts of water, leaving a stirrer like a craft stick in it. The one with the correct proportions will be the strongest. The mixtures with the least and most amounts of water will be structural disasters.
Visual demonstrations can also be used to demonstrate types of bridges. The idea of a cantilever can be shown using wooden blocks or other materials to represent a teeter totter. (See Figure 5.). The same concept of a cantilever can also be demonstrated using two students facing forward with one arm extended straight out to their sides. If a heavy book is placed on each of their palms, it will be difficult to keep their arms extended. However, if they overlap their hands and place a book in the arms hanging down by their sides for balance or counterweight, then they can support more weight of books on their overlapped hands. Their arms act like cantilevers. (See Figure 6.). This experiment has been demonstrated before with a person sitting on their outstretched hands but that would not be recommended in today's classroom (for safety reasons).
The concept behind a suspension bridge can be illustrated using two classroom chairs
spaced at least three feet apart, back to back. If using a 4" length of board, space them at least 4" apart. Using string or rope, drape two lengths over the ends of the chairs so that it looks like a suspension bridge. Cut three pieces of rope or string at least 30" in length and tie one to each of the two strings in the middle between the chairs (like a swing). Then tie one between the one chair and the middle and the other between the other chair and the middle. Lower a plank or board onto your bridge. Have two students pull the strings or ropes taught on each end as books are added onto the bridge to represent load. Test how much weight it can hold and discuss what happens when the students give the ropes too much slack, representing cables that are not anchored well enough to give the bridge adequate structural support. (See Figure 7.) (3)
All general structures need strength, support, and stability. Students can experiment with all three by placing two even stacks of books 12" apart and then placing a "bridge" consisting of a piece of cardstock or of some other stiff paper across the two stacks. They can count the number of pennies or some similar uniform materials that can be placed one at a time in the middle of the paper bridge until it collapses. Then they can fold a piece of paper like an accordion and place it under the paper bridge, adding pennies until it collapses. An arched piece of paper can then replace the folded piece, with the arch touching the top of the bridge and the ends wedged against the bottoms of both sides of the books. Pennies would again be added until it falls. The experiment can be repeated with differing amounts of taped paper rolls or toilet paper holders under the bridge. These could be repeated using a book on top of each end of the bridge. (See Figure 8.). (4) Students would be encouraged to test out their own theories and supports. The results would be discussed and could be placed on a chart. It will be interesting to see if each group of students, using the same materials, obtains the same results.
A quake table will be demonstrated for the students. A teacher from San Francisco (earthquake country) showed me how easy it is to make one using the detached fronts and backs of 3-ring binders. Cardboard could be used, too. Each cover is separated from the next with a little dollar store bouncy ball at each of the four corners. The first two covers are rubber banded together, entrapping the four balls. Then another binder piece is added with another 4 balls separating it from the last one. It is rubber banded to the existing part. Then another layer is added in the same fashion. Just one table can be used to simulate the earth's movements or two of these quake tables can be set next to each other, leaving a gap so that they could represent two hills separated by a raging river. A bridge made out of blocks can be set on it and the tables can be shaken. (See Figure 9). The destructive California earthquake in 1989 lasted for 15 seconds. Shaking the tables for 15 seconds would simulate the length of that quake. That would lead into discussions about safely building structures for certain parts of the country and what that would entail.
Students have different learning styles. Power Point presentations using both visual images and written explanations should help. A video on bridges and footage on You Tube of the famous Tacoma Narrows bridge disaster will add variety and a change of pace for students. To help students see Calatrava as a real person, a section of a You Tube interview featuring him will also be shown.
On our classroom Bridge Wall, I will add examples of the major ideas as we discuss them. To help students visualize the structural principles involved with each bridge type, I will add a drawn illustration of each with arrows pointing in the directions of force. For example, in a simple beam bridge, loading causes compression at the top of the bridge so the arrows would point horizontally inward. Loading would cause tension along the bottom so the arrows would point horizontally outward. The weight of the beam would also push straight downward onto the end supports that hold it up so the arrows would appropriately point downward. These end supports could be abutments, piers or the land itself. Each poster would be marked with these key terms so that the students can add to their architectural vocabulary with each lesson. Hopefully, they will not feel overwhelmed as each small chunk of knowledge is added. The posters that I have made illustrating each type of bridge such as the arch can go on the wall as can any photos of bridges that the students find in magazines or on the web. Vocabulary words can also go on the wall. After its use is explained to the students, for extra credit they can turn in suggestions on a piece of paper for a better name for the wall. The name could be a metaphor like "Bridge Wall: A Bridge of Ideas."
There will be a bridge resource center in the classroom that will include books from the library plus my personal books. A couple books were purchased at a local bookstore in their bargain section for less than $4.00 each and will be additional resources for the students. One has four small puzzles included and these can be laid out for passing students to do as a community effort.
This unit will culminate with an art show displaying the individual bridges that each of my students will have designed and built and then evaluated through discussion and a written reflective thinking piece. Their ideas for the bridges must be inspired by nature somehow. We will go on a field trip to the grounds of the school with sketch paper to get ideas from the environment. The students will be encouraged to be attuned to nature and quietly use their skills of observation, looking up for things like the symmetry of the trees with their branches or at birds in flight. They will need to look eye level with those structures that are on the ground and at everything in-between. Sketching their discoveries that catch their fancy as possibilities will be required because they will need to make the connection to a possible design for a bridge. They need to think abstractly and be willing to stretch creatively, discarding ideas that do not work. At the top of the pyramid of Bloom's Revised Taxonomy is Creating. That is what the students will do with the hands-on activity of creating their own bridges.
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