CS382:Structural-outline

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<Structural Modeling>

Overview

  • This unit on structural modeling will last one week. It will explore the significance and basic concepts of modeling structures using bridges as a case study. We will teach the students how physical structures can be represented and tested from within a computational framework. Bridges are a good example of structures that must be evaluated extensively before they are physically built. Additionally, there are a few programs (Engineering oriented games) that provide interfaces for both building the virtual bridges and testing their weight capacity under variable loads. Students will use a modeling program to test out ideas, and will build and test their structure using K'nex during the lab period.

Background Reading for Teachers and TAs

  • http://www.in.gov/indot/files/bridge_chapter_01.pdf
    • "Bridge building for dummies." Provides an explanation of the duties of Bridge Technicians and defines a number of terms associated with bridge constructions, as well as explaining some of the more common failure points and why they're failure points. This is perhaps unnecessary if the teachers and the TAs possessed a solid knowledge of the subject, but could be extremely helpful otherwise.

Reading Assignments for Students

  • http://pghbridges.com/basics.htm
    • This would make a good read for the beginning of the unit, introducing students to a number of different basic and advanced bridge types, and various tidbits of information about them. If so desired, this could be condensed into a handout.

Reference Material

Lecture Notes

Lecture 1:


Foundations

  • Review key concepts from the units on static and dynamic models, remind people of the difference, and how the two types of models work in conjunction.
  • Why do we want to model bridges and other structures before they are built?
    • Make sure to touch on why it's important to make sure that the construction of structures (such as bridges) is sound virtually rather than gamble on a strong construction in the field.
      • When I (Dylan) took POCO / Software Engineering, I recall a story that Charlie told about why someone he knew (I think it was his father) believed that software engineers, like other professions, should be required to get a governmental license to practice software engineering, due to the fact that now software is important enough and used widely enough that the failure of such can cause a loss of life. I believe that this story is very relevant to this point in the lecture.
  • Explain why how modeling structures such as bridges is different than earlier examples of fire, etc, and how certain key aspects of the procedure and underlying theory are the same
  • Prepare the class to do the lab. If they're going to use bridge builder, this section could be a demonstration of the software and features.


Lecture 2:


Wrap-up/Open Questions

  • Review Components of the Lab.
  • Display a table of each group's lab results, (max load) and might show an picture and give an explanation for the best (most efficient bridge)
  • Explain how best to determine the accuracy of a bridge model.
  • Where can we go from here?
    • Modeling building strain
    • Introduce the 'shake table' and show the split-screen illustration of the model building collapsing on the shake table next to the computer simulation.
    • Does physically constructing a miniture model have any upsides. What about the downsides?
    • Do bridge-builders actually build physical models, or is all the planning done in silico?
    • What are the positive features of using computational models, what are the upsides?
    • How will an increase in processor speeds impact these pros/cons?

Pre-Lab Assignment

Procedure

Students will be instructed to complete a certain number of levels in the software program Bridge Construction Set described below. The first lecture will give them a sense of which designs are most efficient and hopefully encourage them to try to build the most efficient bridge possible, using the fewest number of beams.

Software

Bridge Construction Set

  • A bridge-building computer game. It offers a fairly detailed 3-D OpenGL model visualization. The game is organized into stages of increasing complexity. Demo Available for Mac OS X (Mac Lab anyone?)

Bill of Materials

Lab

  • The lab session will require the students to build K'nex models of bridges they designed in software. This lab will be completed in groups.

Procedure

  • Students will be split into lab groups of an appropriate size.
  • Each group will use Knex to construct the most efficient bridge built in software by a member of that group.
  • When groups are satisfied with their structural model, they will test it's integrity by placing the bridge between tables/chairs/etc and hanging weights off the bridge.
  • We can determine the model accuracy by devising a calculation that determines the appropriate weights to use based on the estimated model parameters of Bridge Construction Set.
  • Groups will then be instucted to determine the point of failure in both their Knex models and their Bridge Construction Set models to determine whether the two models fail at the expected weight thresholds. Again, this will rely on an estimation of what's going on inside Bridge Construction Set.
    • We might be able to contact the developers at Chronic Logic to gain more insight about this.
  • Students should be familiar with wikis by now, so instruct them to insert a picture of their bridge, (taken with the cameras on the imacs) and the max load the bridge could hold into a table in the wiki.

Software

  • This lab will rely on a pre-lab assignment using Bridge Construction Set. The students will have created bridge models in silico, and the goal of this lab is to build those models using Knex.

Bill of Materials

  • K'nex Bulk Pack
    • We diliberated long and hard over whether to use the PASCO bridge set or K'Nex. We decided that K'nex would be a better option for a few reasons.
      • 1. They break. Knex break under load, and this is a positive feature. The Pasco bridge parts are not intended to break but instead are built to be highly durable. To use the PASCO kit to validate the physical model by determining the maximum load would rely on a $399 load sensor kit per group.
      • 2. Breaking things is fun. If the above rational wasn't enough, we both agreed that students will have more fun if they actually get to see the point where their models fail.
  • Weights
    • We will need to procure weights from the physics department to test the Knex models.

Evaluation

CRS Questions

  • After an explanation of some of the concepts in the earlier lectures, have an image comparison of 2 bridges made in Bridgebuilder, ask students which of the two would be stronger.
  • Is this model static or dynamic?
  • Which is stronger; an arc or a triangle?
    • Bridge Construction Set software allows arcs to be constructed out of straight segments. This question will tie together the empirical testing aspect of the pre-lab assignment with the readings.

Quiz Questions

  • Using the framework we've described in the past few weeks of static and dynamic models, explain how you might model a bridge. First define your static model, next define the dynamic process.

<Structural Modeling> Metadata

This section contains information about the goals of the unit and the approaches taken to meet them.

Scheduling

This unit would be well suited for early in the semester. The basic concepts of bridge design are fairly straightforward.

Concepts and Techniques

The relevant discipline here is bridge building, and the skill set will include some basic physics.

General Education Alignment

  • Analytical Reasoning Requirement
    • Abstract Reasoning - From the [Catalog Description] Courses qualifying for credit in Abstract Reasoning typically share these characteristics:
      • They focus substantially on properties of classes of abstract models and operations that apply to them.
        • Sort of. This lab is more concrete. This unit will go early in the semester so it will apply some of the more abstract ideas presented earlier.
      • They provide experience in generalizing from specific instances to appropriate classes of abstract models.
        • Yes, because we're showing how structures and bridges, specifically apply to the abstract model parameters described in the What is a static model and what is a dynamic model units.
      • They provide experience in solving concrete problems by a process of abstraction and manipulation at the abstract level. Typically this experience is provided by word problems which require students to formalize real-world problems in abstract terms, to solve them with techniques that apply at that abstract level, and to convert the solutions back into concrete results.
        • Eh, again, this unit isn't geared towards this as far as I can see.
    • Quantitative Reasoning - From the [Catalog Description] General Education courses in Quantitative Reasoning foster students' abilities to generate, interpret and evaluate quantitative information. In particular, Quantitative Reasoning courses help students develop abilities in such areas as:
      • Using and interpreting formulas, graphs and tables.
        • not really. or maybe... If we use the pasco solution, the beam strength will be documented, and the students can perform basic calculations to figure out whether beams will break under a certain load.
      • Representing mathematical ideas symbolically, graphically, numerically and verbally.
        • The models provide a framework for visualizing physical (mathematical) constraints.
      • Using mathematical and statistical ideas to solve problems in a variety of contexts.
        • This is one context where we're using mathematical and statistical ideas.
      • Using simple models such as linear dependence, exponential growth or decay, or normal distribution.
        • Not really.
      • Understanding basic statistical ideas such as averages, variability and probability.
        • Yes, because the traversal (where we test the bridge by simulating a car driving over it) is a deterministic process. Maybe we could introduce the difference between probabilistic and deterministic.
      • Making estimates and checking the reasonableness of answers.
        • Yes, because students will try to build different types of bridges and determine the 'reasonableness' of their solutions by the simulated test outcome.
      • Recognizing the limitations of mathematical and statistical methods.
        • yes, because the physical model will not account for all variables, such as wind.
  • Scientific Inquiry Requirement - From the [Catalog Description] Scientific inquiry:
    • Develops students' understanding of the natural world.
      • Modeling physical structures is important because the natural world is comprised of physical structures.
    • Strengthens students' knowledge of the scientific way of knowing — the use of systematic observation and experimentation to develop theories and test hypotheses.
      • The students will determine the most appropriate method to build a simulated bridge through both lecture content and trial and error. They will test their models by building physical models of their virtual structures.
    • Emphasizes and provides first-hand experience with both theoretical analysis and the collection of empirical data.
      • The students collect the empirical data by synthesizing lecture content and trial and error. They (potentially in groups) will each devise different models to solve the same problem.

Scaffolded Learning

  • The scaffold pedagogy emphasizes the importance of introducing new ideas and concepts by explaining how those new concepts fit into the context of the material previously covered. Information is contextualized as pedagogical dependencies.
  • Our bridge unit is scaffolded in the sense that as students learn about the structural intricacies of bridge building, they will be able to construct more effective models. The high-level view of bridge types will allow the students to implement these qualities into the bridges they build in the simulator. Once the simulation is complete, the students will build a physical model under the expectations that the K'nex will behave as expected given the test results show by the computer program.


Comments

  • This is good material, and the bridge building effectively shows how the mining of data can be used to make models which then help the creation of new physical manifestations-- but I think this unit needs to narrow down on exactly what it wants to teach. Will this lab have "hard modes" for extra credit? A resolution of the unit's intent will make the lecture outline a lot more coherent. Ditto
    • Yes, there will be opportunities for further investigation during the lab period, including more in depth comparisons between the physical and computational models.
  • Also, the teacher/TAs will have to make sure they got this material under their belt when this lab rolls around, or, as you mentioned above, there will have to be some "reassuring," and we don't want the students to lose faith!
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