Failure Analysis To design a safer building Lesson

Failure Analysis To design a safer building Lesson 2. 3

Structural engineers O Analyze, design, plan, and research structural components and systems to achieve design goals and ensure the safety and comfort of users or occupants. O Make sure that the building or bridges does not collapse. O Build and test scale models

Failure Analysis Involves building a scale model and Testing it with various loads to see how strong it is and where it breaks, or “fails. ” The goal of this process is to identify weak aspects of a design and possible failure sites, so that the design can be strengthened before construction starts.

Design challenge O This is a team activity in which you and your teammates will go through the engineering design process to design and build a tower, and analyze how it failed.

1. Define the problem Problem Statement O Design and build a prototype of the tallest tower that supports the largest load, with the least cost. O Test the prototype and identify the weak points and types of failure. O Write a report, describing what you accomplished and what you learned.

Criteria A successful tower design will O Be at least two feet high O Support a live load of at least a 500 mlbottle of water O Be free standing O Have a 3”x 3” platform to place a load

Constraints The materials used for construction of the prototype are limited to O Notebook paper O Straws O Masking tape O Paperclips

2. Research the problems O Think about the forces that will act on your tower. When a load is applied, the tower will act as a system to support the load. But different components of the system will be subject to different forces.

Tension O A stretching force that happens when you pull the ends of an object apart.

Compression O Compression: a squeezing force that happens when you push the ends of an object together

Tension + Compression = bending

3. Develop Possible Solutions Sketch two to three different ideas. Think about the following: O Which materials are strongest for use in tension or compression? O How can these materials be shaped so they will be stronger? O How can the materials be fastened so the joints are strong? What design elements will make the tower tall and stable? O What design elements will hold up heavy live loads? O What design elements will make it an attractive structure?

4. Choose the best solution O Complete the Pugh chart O Strength O Height O Least expensive O Sketch the design

5. Create a Prototype O Price O 1 notebook paper: $1000 O Masking tape, per inch: $600 O A straw: $900 O A paper clip: $750 O Discuss what you need

COMPETE!! O Height O 4 points for the tallest tower O 3 points for second, 2 points for third, 1 point for fourth. O Strength O 5 points for fully-supported tower O 3 points for partially-supported tower O Cost-effective O 4 points for the cheapest tower (3, 2, 1) O 3 points for second, 2 points for third, 1 point for fourth.

Test and Evaluate Does it Meet the Criteria? O Measure the height O Calculate the final cost O Test for weight.

Failure Analysis Next, you will analyze how and why the building fails and how it can be improved. O Carefully add weight little by little until the tower just begins to fail. O Record the maximum weight. O Identify weak points of the building O Identify which forces below cause failure.

Basics of Failure Analysis Has 4 main areas. O Failure modes O Suddenly or gradually? O Failure site O Where in the object failure occurred O Failure mechanism O What physically happened in the failure O Root cause O The aspect of design, defect, or load that lead to the failure.

Terms of Failure Analysis O Elastic Deformation O Material returns to its original shape O Elastic Limit O The material does not return to its original shape any longer. Plastic deformation begins O Plastic Deformation O The material does not return to its original shape any longer. O Failure Point O The material breaks

4 Types of Materials O Elastic materials O Plastic materials O Brittle materials O Malleable material

Elastic materials O Change their shape when under a load, but return to their original shape when the load is removed. O Example O Rubber, A diving board, Anything else?

Plastic materials O Also change their shape but remain permanently deformed O Example O Melted plastic, plastic bag, anything else?

Brittle materials O Break or crumble rather than deform under a load O Example O Concrete, brick, anything else?

Malleable materials O Can easily be shaped by hammering or rolling, and keep their new shape. Some materials can be made more malleable by heating. O Example O Aluminum foil, copper, anything else?

More types of forces O Torsion: Twisting force O Shear: It occurs when part of an object is pushed on way and another par of the object is pushed in the opposite direction

Safety Analysis O

Benefit/ Cost Analysis O

Communicate Write a report of your tower project. O Picture of Failure Analysis O Sketch your tower before it fell, labeling the various components of the tower and why they are there. O With a colored pen or pencil, identify each of the weak points in the design, writing in the type of the force that caused the failure.

Report should include O Why is your tower a good design? O Did it meet the criteria and constraints of the problem? O How safe is this design? O What are the weakest points under extreme live loads? What is the benefit cost ratio of your design?

Redesign O If you design and build the tower one more time, how would you redesign the tower so it is taller, stronger, or less expensive?