CKY IB Design Technology

Name: _______________________

Class: ________

HL Topic 9 Structures

Your Job

Design 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 steel

Some 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

IA: Bridging the gapAssessment Criteria – Research (R) and Development (D)Due: June 26th 2012

Aspect 1 Aspect 2 Aspect 2

Creativity Techniques Solution

Complete

/ 2

Uses a range of innovative ideas to solve the problem, at least 6 varied design sketches showing details and descriptions

Uses freehand sketching, isometric and perspective. Includes the use of computer modeling (CAD) and other creative methods of presentation

Arrives at a good solution that is practical, functional, solves the design problem or need and is aesthetically pleasing

Partial

/ 1Only approaches a limited amount of innovative ideas to solve the problem. Ideas do not vary and lack creativity

Presents ideas using a range of techniques but not to the extend as above.

Satisfactory solution to the problem is reached, some aspects are still unresolved and need modification or improvement

Not at all

/ 0Idea generation is mundane or irrelevant. There is not a specific use or no development from what is already available

Does not use various techniques to communicate design idea or the techniques used are inappropriate

Does not arrive at a solution or the solution is not appropriate for the design need

Not at all

/ 6Comments:

Development (D) Development

Creativity

oYou have 5-6 original and creative ideasoYou have used freehand sketching to show your ideasoSketching and written information is completed to a high standardoYou have annotated manufacturing methods and joining techniques suitable to your solutionoYou have explained how your design meets your design specificationoYou have explained strengths and weaknesses of your designoYour research has informed your design ideas

Techniques

oYou have used freehand drawing techniques. oYou have used isometric drawing techniques. oYou have used exploded drawing techniques. oYou have used perspective-drawing techniques. oYou have used CAD drawing techniques.

Solution

oYou have described your final design in detail.oYou have used correct symbols in your working drawing. oYou have included dimensions on your solution. oYou have listed joints/construction techniques. oYou have a parts list. oYou have listed tolerances for your solution. oYou have explained the finish of your solution. oYou have listed the materials needed to make your solution. oYou have a detailed plan of production.

Po Leung Kuk Choi Kai Yau School - Internal Assessment Criteria – Development – SL_HL

Student: Teacher: Miss Gee Date:

Investigation/Project: Topics/option: Hours:

Aspect 1 Aspect 2 Aspect 3

Strategies Data collection Data processing and analysis

Complete

/ 2

Identifies a range of suitable resources and strategies for research.Has very clear priorities for research that link well with the brief or research question.

Collects a wide range of appropriate research material. The research balances both qualitative and quantitative and secondary and primary research methods. Represents information in many different forms.

Processes research material astutely with detailed analysis. Final analysis allows for the development of ideas. Analysis supports the usefulness of the study and links this to the design brief or question. Good recognition of any errors. Transforms all data appropriately.

Partial

/ 1Identifies some suitable resources and strategies for researchResearch is planned and links to the design brief or research question.

Collects some appropriate research material. Some different methods of research used and some information represented appropriately.

Processes research material appropriately however analysis is limited. The analysis doesn’t always link closely to the design brief and these errors are not always monitored. Only some data transformed usefully.

Not at all

/ 0Does not identify suitable resources and strategies. Any strategies are teacher led.

Does not collect any appropriate research material.

Processes research material inappropriately.

Not at all

/ 6

Comments:

Research (R) 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

Po Leung Kuk Choi Kai Yau School - Internal Assessment Criteria – Research – SL_HL

Student: Teacher: Miss Gee Date:

Investigation/Project: Topics/option: Hours:

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 folio

You 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 Evaluation

A 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 specifications

Compile 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

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.

External load acting on a structure

Body load

Forces research (use forces link in the appendices):

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.

Bridges research moodboard

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 strainWe know that: Tensile stress = __force___ = F area A

Tensile strain = ___extension __ = e original length l

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

Draw a diagram showing necking and failure

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.

Terms you need to research to help the project

• 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

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.

Mechanical properties of materials

DuctilityResiliance ToughnessElongationBrittlenessElastic limitYield stressUltimate stressBreaking stressYoung’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.

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

Bending moment = Force x Distance

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 strainTensile 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 questionsWhat 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 Modulus

http://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 researchSuitability/ appropriateness of structureCreativity or solutionCommunication and explanation

Must be all compiled into an online folio document