CSC 110 - PA 4 - Bridge Deflection

By the time you start this full PA, you should have already completed the two short PAs. You should reference or even re-use some of that code to work on this!

Inputs

Your program should take 4 inputs. The input prompts, along with sample input values, are shown below:

Bridge length:
50
Spacing between supports:
10
Spacing between points to measure deflection at:
15
Weight:
1000

The length of the bridge represents the length of the span of the bridge in meters. The second input is the spacing between the bridge supports, in meters. The third input is the spacing between the points along the bridge to measure deflection at. You will be required to calculate the deflection at each of these points. Finally, the last input is the weight to use for the deflection calculation.

Output

Given the 4 inputs shown in the previous section, the output of the program run should look like so:

Bridge length:
50
Spacing between supports:
10
Spacing between points to measure deflection at:
14
Weight:
1000
                 0              1              2
EEE##################################################EEE
EEE          #          #          #          #      EEE
EEE          #          #          #          #      EEE
EEE          #          #          #          #      EEE

DEFLECTIONS:
    point 0 = 0.1873
    point 1 = 0.15714
    point 2 = 0.05873

The top part of the output is a text representation of the bridge. Each end of the bridge is represented with E characters and a #. The bridge itself is represented with #. The supports are also shown, at intervals that correspond to the spacing between supports input. At the top of the bridge, various points are annontaed with numbers. These are the points on the bridge that you should calculate the deflection at. These points are controlled by the fourth input.

The diagram below shows the parts of the bridge and labels that are controlled by 3 of the 4 inputs:

Given this bridge, let’s go over how the deflections will be calculated. Point 0 is between the first and second interior supports on the bridge. It is four dashes (meters) away from the left support and 5 dashes away from the right. Thus, the distance 4 should be plugged into the formula. The provided force (weight) was 1000 Newtons. Going through the steps:

y = ( (w * x) / (48 * E * I) ) * ( (3 * L**2) - (4 * x**2) )

y = ( (1000 * 4) / (48 * 210 * 500) ) * ( (3 * 10**2) - (4 * 4**2) )

y = ( 4000 / 5040000 ) * ( (3 * 100) - (4 * 16) )

y = ( 4000 / 5040000 ) * ( 300 - 64 )

y = ( 4000 / 5040000 ) * 236

y = 0.18730

You should do this calculation for each of the points along the bridge.

Development Strategy

Here’s how we recommend working on this program.

• Get all 4 of the inputs from the user. You do not have to validate these.
• Copy over the bridge printing code from the short PA. This is a good start for printing out the bridge portion for this PA! Make sure it uses the user input(s) to size it correctly.
• Add in the point printing, which is based on the point spacing input value. Don’t worry about calculating the values yet, just get the numeric labels in the correct location on the bridge. You can add this component to the loop(s) that you used to print out the bridge.
• Create a new while-loop that you can use to calculate the deflections. This loop will repeat, and make a deflection calculation for each point. Initially, you can make the calculations assuming that there are no in-between supports, just the two ends of the bridge. There are a bunch of test cases for this!
• Lastly, if you have time, work on getting the calculations working for when there are one or more internal bridge supports.

Other

• You may not use string multiplication.
• You will probably want to use at least 3 loops, but you may use more if you need to.
• You should follow the style guidelines linked to on the class website. This includes naming variables well, having good comments, and structuring your code well.

Submission

Submit bridge_deflection.py to gradescope by February 5, 2019 at 7pm. You should do your best to make sure that all of the test cases pass.