Weston Middle School
Massachusetts Grade 8
Technology/Engineering MCAS Review
| Syllabus: Grade 7 Design-Construction | |||
| Lesson (Periods) | Key Ideas | Description | Materials |
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I (2-3) Floppy Towers |
Technology= Knowledge of techniques - How to make things Each change in technology- stone age, bronze age, iron age, invention of concrete, invention of arch, electronics—has changed society Examples:
Engineering: Engineering(one definition) is designing a solution to a human need based on a (mathematical ) model of materials, which is good enough for the required task. It does the job, with an adequate margin of safety, but is not wasteful. Example: Pizza Engineering: How many pizzas do you order if 10 friends are coming for a pizza party? Engineering Model: Average person eats 2 slices, but some might eat more. Calculation: If 8 slices per pizza, you might order 3 pizzas( safety factor of 2 slices) or 4 pizzas ( safety factor of 10 slices).
The most efficient design is the least expensive one that meets the performance criteria
Here is an example of an elegant web page design:
For Apple Computer, its famed elegance in design is as much about what to leave out as about what to include. Failure- carefully analyzed- is essential to engineering design, as it reveals the weak points of structures and their design limits .
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Lesson 1: Columns:
Lesson
2
Discussion: Lesson 3
Lesson 3-4: Alternate application: Stays on ship mast rigging.
Based on Wimpy Antenna by Doug Prime Discussion:
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Office Paper Cotton String Tape 1/4" dowels Tape Measure |
| Designs that use standard components are easier and less expensive to design with and build. Example: Unistrut Space Frame, Chestnut Hill Mall Roof.
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Engineering Example: How many bolts does it take to hold up a concrete ceiling panel? Proper engineering design requires that designs be tested to failure to insure that there is an adequate margin of safety in the strength/reliability of design. While overbuilding and testing of a design causes projects to cost too much, the reverse can be disasterous, and in the end cost many times more In the summer of 2006, concrete ceiling panels in a 'Big Dig' tunnel fell on a car and killed a woman passenger.
Not knowing how a design will fail can have disasterous consequences - in the collapse of the tunnel ceiling of the Big Dig, the need to reduce costs and construction time overrode the need, through testing, to insure the safety of the design. |
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TV tower, Needham, MA: Tower is in compression. Guy wires( in tension) permit a much thinner than would be needed otherwise. |
TV tower, Newton, MA: Neighborhood restrictions against guy wires required a tripod design. |
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II ( 1 ) Structures |
Tower
is a Structure- materials that maintained a shape
( vs decorations, etc.)
Forces that act on it include tension and compression Other forces include torsion (arm twisting), bending (illustrate with sponge), and shear All structures fail when excessive loads are placed on them. Engineers need to know when structures will
fail- knowledge of failure properties (load limits) is critical
Are you tense? Need some structure to your life? Then tune in to Bill Nye the Science Guy as he explains the science of structures. All structures give support or create a shape. You can find structures everywhere. Bridges, buildings, chairs, shoes, plants, spiderwebs, tables, and even your own body are all structures. A structure's shape, size, and what it's made of depend on what the structure does and how strong it needs to be. When structures give support, they either experience a pull (tension) or a push (compression). Structures in tension, such as ropes, cables, or blimps are made from stuff that is good at pulling. The materials in tension are usually thin. Structures under compression, such as elephant legs and courthouse columns, are made from hard stiff stuff. Compared to structures under tension, structures under compression are much thicker. When it comes to structures, form (the size and shape) depends on function (what it does). Build support for Bill by watching the "Structures" episode. -http://www.tv.com/bill-nye-the-science-guy/show/9135/episode_guide.html
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Mini-Activities-to Do in Pairs: See more activities at Building Big Educator's Guide Extra time:
Social Studies Connection: Roman Concrete Failure in tension and compression- Laval Overpass Collapse, Montreal, October 2006 Beams Lesson
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Video: Structures (Bill Nye) Sponge Stack of wood Cinder Block Cotton String |
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III(3) |
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In computer lab: |
Concrete Block Video: Building Big |
| Building Big:
Mathematical Links: |
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IV( 4) Straw or Paper Bridges |
Challenge: Build a truss bridge 24" long using plastic straws, pins, and cardstock which will hold at least 8 small water bottles. Grade will depend on strength and efficiency( capacity/ weight of structure) of bridge. Just as a great general concentrates his forces where they are needed, an efficient design engineer puts the most material where it is most needed . I-Beams are strengthened most by increasing their web(height) dimension, because of the direction of the applied load.
Lesson 1: Build deck using standard design :
Lesson 2: Making side trusses using foam board jig- try different designs Lesson 3: Attach trusses to deck. Add top and end trusses- there are three dimensional planes. Lesson 3-4: Load Test to close to failure- analyze weak points- redesign Test for efficiency= Live Load( capacity)/ Dead Load( weight of bridge)
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Reference: Mario Salvadori, The Art of Construction Alternate I- Paper Beam Bridges
Lesson 2:
A beam or girder bridge on the Mass Turnpike in Weston Lesson 3:
Lesson 3/4:
If done- improve bridge; tape joints, assist other students; make small arch bridge or suspension bridge |
Plastic Straws Pins Water bottles 110 lb cardstock, 8-1/2" x 11" Optional: Truss Templates Deck Templates |
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V (3) West Point Bridge Designer
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Engineering structures are typically designed, tested, and optimized using engineering simulation programs.
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Lesson 2:
Extra time- work on own design Lesson 3:
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Other Bridge types |
Tufts Arch-Bridge Demo Model |
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VI(2) Home Construction- Site Selection |
Introduce
House Model Project
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Show photos Build architectural site model- discuss :
Video: House Construction See also |
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VII(3) Home Designer |
Handout: House Styles Demonstrate using home design software.
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Design House using CAD program( Punch Super Home Suite)
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VIII (1) House Model- |
Foundations provide a firm support for a building structure, as well as isolating wood components from moisture and insects in the ground. The type of foundation required depends upon the ground conditions. The width of the footings depends upon the compressive strength of the soil/ground- the softer the ground, the larger the footing is required. Tall buildings are usually built on foundations that extend to bedrock. Types of foundations include concrete posts, slab foundations, and foundation walls with footings. |
Activity:
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IX(2) House Model- Sills |
A sill beam, lying on top of the foundation, supports the rest of the structure.
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Demonstrating measuring and cutting sill beams using miter saws. Construct sill atop drawing plan.
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| X(2) Platform Framing |
Platform framing constructs floors and walls out of stick-built structural panels. This is the most common home-construction method in the US. Platform framing uses inexpensive materials and is easily learned by construction workers. Floors beams are called joists. Width of beams determined by spanned distance. Floor joists today are commonly engineered beams , as these are lighter, stronger, and less expensive than sawn-lumber beams and are available in any length.
Vertical structural elements are called studs. |
Engineered beams, made largely from waste, are much more efficient than solid beams |
1cm x 1 cm x 40 cm wood, 0.4 cm x 1 cm x 40 cm wood Glue guns Hot glue sticks Floor joist sample assembly |
| Post and Beam Framing | Post-and-beam framing uses large wood or steel vertical and horizontal elements ( posts and beams) to form the structure of the house. Post-and-Beam framing ( called timber framing when using wood elements) has the advantage of greater flexibility in floor plans, as the only vertical structural elements are posts, permitting owners to more easily customize and adapt structures to their needs. For wood buildings this advantage is offset by higher costs for materials, due to the scarcity of large construction timbers, and the higher skill level required to accurately construct such buildings. Post-and-beam framing is more typically seen in steel-framed commercial buildings.
In colonial times, most wood structures were built using this construction method. However, in the 1800's, as large trees became scarce, and fewer builders were skilled joiners, this method was replaced by balloon framing and platform framing. In the last thirty years, however, there has been a resurgence of interest in timber framing, as computer-based design and manufacturing have simplifed fabrication. In addition, timber framing has become integrated with new concepts in design, called Open Building.(pdf) Open Building using specialized utility modules and raceways to permit utility systems to be easily modified, without requiring the expensive modifications needed in platform framing. |
Links:
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XI(4) House Model- Wall Framing |
Platform framing has standard 8 foot or 10-foot ceilings to enable use of ready-made studs. Windows and doors must be rough-framed to accept factory-made components .
Stairs are framed using pre-cut beams called stringers to supports the treads and risers. |
Rough framing of stairs showing stringers and rough treads. These are later covered over with finished stairway materials prepared off-site by specialized manufacturers. |
1cm x 1 cm x 40 cm wood, 0.4 cm x 1 cm x 40 cm wood Glue guns Hot glue sticks Wall frame sample assembly |
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XII(3) House Model- Roof Framing |
Nearly all roofs are framed using one of two methods: standard stick framing or newer truss framing. Stick-framed roofs utilize individual rafters that span from the top of exterior walls to the ridge. Truss-framed roofs are built from triangular-shaped, pre-made truss units. Gable and hip roofs may be built primarily of trusses; other roof shapes, particularly those with dormers or on houses with cathedral ceilings, attic rooms or attic storage areas are stick built. Stick framing creates a triangle between rafters and ceiling joists. Collar beam adds strength at the middle.
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Demostrate how to create roof lines and install rafters. Build top floor and Roof as a separate unit- needs to be removable for modeling purposes Modified Stick
Method: Continue with Roof Framing- put steps for ridgeboard on board- uprights+ ridgeboard + rafters
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XIII(2) House Model Sheathing and Insulation |
Once a house is framed, it must be sheathed to achieve a finished appearance.
Sheathing Includes:
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XIV(1) Summing Up |
Review Parts of a Building-
o Excavation |
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| Community Planning/Cluster Zoning | |||
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