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Assessment Criteria – Research (R) andDevelopment (D)

Due: June 26th 2012

IA: Bridging the gap

Your JobDesign needYour company wants to build a transport bridge that can span from Hong Kong to Macau or a pedestrian bridge that can give people access from Hong Kong Island to TST.Owners requirementsChoice between two outcomes:A bridge that will transport vehicles from Hong Kong to MacauA pedestrian bridge to transport people from Hong Kong to TST Preparation for SubmissionResearch on existing productsReport showing bridge analysis and construction requirements, forces acting on structures, factor of safety3D CAD and development of design for prototypingTesting Prototype – using modeling materials instead of steelSome possible tasks:Research truss configurationsCreate the structural modelCheck static determinacy and stabilityCalculate reactionsCalculate internal member forcesDetermine member sizesCheck member sizes for constructabilityDraw plans.Build the bridgeResearch forces acting on – Forces labCreate a mood board of different types of bridgesLook and study the different types of bridgesFour types of bridges: Arch, beam, suspension, and cable-stayed

Development

Creativity

- You have 5-6 original and creative ideas
- You have used freehand sketching to show your ideas
- Sketching and written information is completed to a high standard
- You have annotated manufacturing methods and joining

techniques suitable to your solution

- You have explained how your design meets your design specification
- You have explained strengths and weaknesses of your design
- Your research has informed your design ideas
- Techniques
- You have used freehand drawing techniques.
- You have used isometric drawing techniques.
- You have used exploded drawing techniques.
- You have used perspective-drawing techniques.
- You have used CAD drawing techniques.
- Solution
- You have described your final design in detail.
- You have used correct symbols in your working drawing.
- You have included dimensions on your solution.
- You have listed joints/construction techniques.
- You have a parts list.
- You have listed tolerances for your solution.
- You have explained the finish of your solution.
- You have listed the materials needed to make your solution.
- You have a detailed plan of production.

Checklist – Research

Strategies

A written research plan with priorities of what you will research

Primary and secondary sources of data

Identified both qualitative and quantitative data

Correct referencing where appropriate

Data collection

Research and data is focused and appropriate to project

Balance between qualitative and quantitative

Presented research in a variety of forms (graphs, tables, diagrams, drawings and photographs

Research and data includes labelling and explanations of outcomes

Data processing and analysis

You have processed raw data and presented in an astute (clear) manner

You have transformed data into a suitable form for analysis (graph, table etc)

Your written analysis is detailed and explains how your design brief can be answered

You have analysed the relevance and usefulness of your data

You have identified any errors or uncertainties you encountered throughout your research/ data

You have assessed and commented on the reliability of your data

You have used correct referencing

The weight of the bridge will be recorded. The bridge will then be placed upon a testing stand which will consist of two surfaces, level with respect to each other and separated by 20cm. A bar will be placed across the roadbed (perpendicular to the bridge's length) at the weakest looking point of the bridge (a bridge being no better that its weakest point) and the weight adding mechanism suspended from this bar. Weight will be added at a slow, steady rate until the bridge collapses or sags to 90% of its original height. At this point, the total weight suspended by the bridge will be recorded.

Scoring:

The score for the bridge build event is determined by the following formula

(efficiency of a bridge):

score = (mass supported)/(mass of bridge).

The points will then be scaled to a maximum of 100 points.

Assessment of testing of prototype

Procedure:

The weight of the bridge will be recorded. The bridge will then be placed upon a testing stand which will consist of two surfaces, level with respect to each other and separated by 20cm. A bar will be placed across the roadbed (perpendicular to the bridge's length) at the weakest looking point of the bridge (a bridge being no better that its weakest point) and the weight adding mechanism suspended from this bar. Weight will be added at a slow, steady rate until the bridge collapses or sags to 90% of its original height. At this point, the total weight suspended by the bridge will be recorded.

Scoring:

The score for the bridge build event is determined by the following formula

(efficiency of a bridge):

score = (mass supported)/(mass of bridge).

The points will then be scaled to a maximum of 100 points.

Final Submission (use the development criteria as a guide)Must be an online folioYou must include the following:Moodboard on bridgesResearch into loads and forcesResearch into materials for bridgeResearch into different structures and beamsLabelling of loads on your bridgeDevelopment drawings of your bridgeTechnical drawing of your bridgeTesting prototype of truss bridgeTesting and EvaluationA successful project will explain the following extensions of learning:How the factor of safety is used in designHow scientific principles, mathematic tools, engineering concepts, experimental data, and practicalconsiderations contribute to the engineering design processHave a model bridge to meet a set of design requirementsBuild a model bridge, consistent with a set of plans and specificationsCompile your research project, images of testing prototypes into an online portfolio, they will be reviewed by a civil engineer practicing in Hong Kong. Review points:Adequacy of research Suitability/ appropriateness of structureCreativity or solutionCommunication and explanation

Show the different forces that can act on beams: compressive, tension, torsion, bending, shear.

Explain your results of testing the connection points of the various shapes – square, pentogram, heptagon. Which shape was strongest and how did you add support to various shapes?

Look at the following images of products and explain the importance of consideration of stress and strain on material choices and design of products.

Four main types of bridges

Task:

Draw a quick diagram of your bridge in 2D front view and label the external load and body load acting on it

Young’s modulus

Young’s modulus is concerned with simple stretching (or compression), in which an applied force increases or decreases the length of a sample of material without altering its density.

The Young Modulus is defined as the ratio of the tensile stress and the tensile strain within the elastic region of the stress/ strain curve.

So we can write: Young modulus = ____tensile stress____

tensile strain

We know that: Tensile stress = __force___ = F

area A

Tensile strain = ___extension __ = e

original length l

So we can write: Units for the Young Modulus are Pascals (Pa) or newtons per square metre (Nm-2).

The Young Modulus describes pulling forces.

Stress strain curve – Colour and label the elastic region one colour and the plastic region another

Draw a diagram showing necking and failure

Terms you need to research to help the project

Newton’s First Law: An object in motion will stay in motion unless acted upon by an outside force. An object at rest will stay at rest unless acted upon by an outside force.

Newton’s Second Law: Fnet = ma

This law says that if a force is applied to the bridge it will accelerate in the direction of that force. If the forces all add up to zero the bridge is in equilibrium and does not move.

Newton’s Third Law: For every action there is an equal and opposite reaction. If a car is on a bridge it is exerting a force on the bridge, therefore the bridge must be exerting the same amount of force on the car. If the bridge is not moving it is in equilibrium and all the forces will add up to zero.

- External load
- Body load
- Weight
- Mass
- Equilibrium
- Structures
- Strength
- Beam
- Sections of beams
- Tensile and compressive forces
- Stress and strain curve
- Deflection
- Stiffness
- Bending moment
- Factor of safety

Mechanical properties of materials

Ductility

Resiliance

Toughness

Elongation

Brittleness

Elastic limit

Yield stress

Ultimate stress

Breaking stress

Young’s modulus

Weight vs Mass… what would you weigh…

Weight- The gravitational weight of a body is the force with which the Earth attracts the body. This force is proportional to the body's mass and depends on the location. Because the distance from the surface to the centre of the Earth decreases at higher latitudes, and because the centrifugal force of the Earth’s rotation is greatest at the Equator, the observed weight of a body is smallest at the Equator and largest at the poles. The difference is sizable, about 1 part in 300. At a given location, the weight of a body is highest at the surface of the Earth; it diminishes with altitude and with the depth below the surface. For example, the weight of a body diminishes by about 0.1% if it is raised 3 km above the Earth's surface or taken 6 km below the surface. Weight also depends to a smaller but measurable degree on the density of the Earth's crust below the body.

Mass- Isaac Newton said that the mass of a body is the measure of the quantity of matter the body contains. Quantity here does not mean volume. Mass can be thought of as the tendency of a body to resist the change in velocity caused by an external force. Mass is therefore said to be a measure of inertia. It has magnitude but not direction and is therefore a scalar quantity. The SI unit is the kilogram (kg).

Task:

http://www.exploratorium.edu/ronh/weight/

Weigh your self and fill in the weight and mass on the various planets. Choose three of your own. Show all calculations.

Extension question: Explain why your weight varies on the different planets.

Bending moment = Force x Distance

Beams

Task:

Research the various types of beams, use technology student and your bridge research to help you.

http://www.technologystudent.com/forcmom/force2.htm

Units – Newton Metres (Nm)

BeamsName: ________________ Class: ___________

Beams bend and flex due to the mending moments. Different types of beams are then required in order to cater to various design requirements.

1. Research the different materials used for beams and explain positives and negatives of each, solid wood, concrete reinforced, metal sections.

2. Draw the different type of metal sections you can get in beams.

3. Discuss the economical or structural reasons for using different types of beam cross sections.

4. Draw diagrams to show the three types of beams: Cantilever, overhanging and simply supported.

5. Below is an image of a shading using LVL (laminated veneer lumber). Research and explain the benefits of using LVL beams in construction, consider – design, stability, manufacture. Show examples of existing products.

6. Why would factor of safety be important with the design of beams? Explain your answer with examples from their use in real design situations.

Formula:

Young modulus = ____tensile stress____

tensile strain

Tensile stress = __force___ = F

area A

Tensile strain = ___extension __ = e

original length l

Units for the Young Modulus are Pascals (Pa) or newtons per square metre (Nm-2).

Stiffness – load

deflection

Factor of Safety = Design load (UTS)

Normal maximum load (stress)

F = Ma

End of Topic focused questions

What is the correct definition for Young’s Modulus?

Give examples of what it means by Yield Strength of a material?

What is the difference between Plastic and Elastic strains?

Draw how the force is effecting a beam that is contracting body load?

Write down a definition for Mass?

Draw a body is experiencing Tensile forces?

Draw a diagram showing deflection taking place?

Describe what is meant by a bending moment?

What is the factor of safety?

What is the definition of Stress?

Strain is defined as the amount of deformation an object experiences compared to its original size and shape, how is this shown as a formula?

Appendices

Useful websites:

http://www.pbs.org/wgbh/buildingbig/bridge/basics.html - types of bridges

http://www.pbs.org/wgbh/buildingbig/bridge/truss_forces.html - forces

http://www.ccmr.cornell.edu/educa)on/modules/documents/PhysicsofBridges.pdf

http://www.pbs.org/wgbh/buildingbig/bridge/challenge/index.html

http://www.fhwa.dot.gov/bridge/steel/pubs/if12052/volume01.pdf - information on steels to be used in bridge construction and information on alloying, heat treatment, beams, Youngs Modulushttp://www.fhwa.dot.gov/bridge/steel/pubs/if12052/volume05.pdf - Information on types of bridges

http://www.evolo.us/category/competition/

Due June 26th

Compile your research project, images of testing prototypes, they will be reviewed by a civil engineer practising in Hong Kong.

Review points:

Adequacy of research

Suitability/ appropriateness of structure

Creativity or solution

Communication and explanation

Must be all compiled into an online folio document

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