Fairly Fundamental Facts About Forces and Structures 4

Through hands-on group projects, students learn about the force of compression and how it acts on structural components. Using everyday materials, such as paper, toothpicks and tape, they construct structures designed to (hopefully) support the weight of a cinder block for 30 seconds.

When civil engineers are asked to design a building, one thing they must calculate is the total compressive load that will be at work in the structure. To do this, they take into account the anticipated loads resulting from how people will use the building and the weight of the structure itself. Based on these calculations, materials with appropriate properties for carrying the weight are chosen, and structural components (such as columns and beams) are designed to provide adequate support and weight distribution. compression force load structure support Students gain insight into structural supports designed to withstand compression. Students develop construction skills. Students learn about the fundamental loads. cinder blocks (or uniform text books) Per Group: piece of wood (a smooth flat object to put the cinder blocks on) 4 3"x5" index cards 8.5"x11" copy paper 8.5"x11" plastic transparency 12" masking tape 15 toothpicks (optional) (optional) 2 drinking straws ruler scissors safety glasses, 4 pairs Name for me some "strong" materials. (Listen to student ideas. Write them on the board. Expect students to suggest steel, concrete, wood., etc.) Would you believe that a piece of paper, used correctly, could support the full weight of a cinder block? A pushing or pulling action that moves, or tries to move, an object. Objects that can hold up weight and withstand forces that are placed on them. Examples: buildings, bridges, dams, planes, bicycle. frames. External forces that are acting on a structure. An internal force that develops inside materials that resists outside forces and fights to hold a structure together. Two pushing forces, directly opposing each other, that squeeze an object and try to squash it. For example, standing on an aluminum can, squeezing a piece of wood in a vise; both the can and the wood are in compression or are "being subjected to a compressive load." Do the "Introduction to Loads on Structures" activity, to help increase what the students will be able to understand from doing the activity. Gather materials. Set-up a safe test area. Problem Statement: Using the material provided, have teams of 3-4 design and build a structure or structures to hold a concrete cinder block at a height of 3" above the floor for 30 seconds. More cinder blocks will then be added until their structure fails. Allow the students 10 minutes to brainstorm, during which time the students need to sketch their design ideas. When the time is up, pass out the materials. The maximum amount of time allowed to build the structure will be 15 minutes. Testing takes place in the test area where all students are required to wear safety glasses. Have each team place their structure(s) on the floor and position the board onto their structure. Once it is in place, have two team members slowly and carefully lower the block onto the board. Advise the students that they should be mindful of placing the cinder block as flat as possible on the board to limit any twisting forces on their structure. Have the students who are not placing the block carefully watch their structure to see where and how it fails. After 30 seconds the structure will be deemed successful. More weight can be added until failure is achieved. !!Warning!! Watch out for fingers and feet during testing! What is compression and what effect does it have on structures (structural elements)? Give examples of compression and find real life examples of structural elements that are in compression. How did your structure fail? Did it twist or slide to one side as it collapsed? If so, what do you think caused your structure to fail this way? Rubric for Performance Assessment (doc) Rubric for Performance Assessment (pdf)