River Pollution Lab–Questions

Question

One of the questions for the lab memo asks "How should the treatment plant be operated?" What exactly are you looking for with this question?

Response

You are to take everything you know about the purpose of a treatment plant and how it operates into consideration in making recommendations about what steps must be taken to address the spill.  They would certainly include closing the water intake at some point as well as reopening it later.  There may well be other steps that would be helpful.

Bridge Lab–Strain Gage Location

Question

I’ve found the location of the strain gauge where we were looking at but I am not sure what numbered sensor it was in terms of the sensor data we were provided. I am assuming it was sensor #1?

Response

The file READ ME – Data description 20121018.docs describes the gauge locations.  We could see the one on the sidewalk side, so it’s the “identified” one.  That file asks you to pick the best one or an average of some or all of them.  You’d describe in your memo on why you made the selection.

T-P Bridge Questions

Question 1

I'm a little unsure of where to get the data to find the strain gage cross sectional area. I used the measurements from page 19 of the "Tacony-Palymra Drawings" PDF provided on BB Learn. However, there is a space in the excel lab for additional plate measurements, but I didn't see any additional plates on the page 19 drawing, so I'm not sure if I'm using the right data.

Response 1

You’ll find full information on the construction of the truss chords on p.12.  What you have to do there is figure out where along the truss to interpret the construction of the chord.  To do that you have to know where the strain gage is located (you’re told 82’ from the support).  In order to determine where that is on these drawings note that the Tacony and Palmyra sides are symmetrical and that the support point is at the end of the bascule span on the Palmyra side.  The dimensions on the drawing should help you figure out between which Uxx points the chord information is provided.  As a hint I think you’ll find that there are plates.

Question 2

for question 3, which direction is the diagram in the lab description facing? Which side of the bridge is the strain gage pointed out in the diagram on?

Response 2

We were walking towards Palmyra on the south side of the bridge and passed the strain gage on that side.  You can use the shadows in the truck image as well as Google Maps to determine which direction the truck had to be heading and thus determine the correct orientation of the diagram.

Question 3

For question 4, which asks us to estimate the weight of the truck using moment equilibrium by estimating the distance from the support of the truss to the location of the strain gage and the distance between chords, (again) I'm unsure if I'm using the right data. I used page 19 from the bridge drawings again for this question, and estimated the distance between chords to be 134.75 inches and the distance from support to strain gage to be about 714 inches. Am I looking at the correct truss? I'm using the lower image of the truss on page 19. 

 

Response 3

Look at the title on p.19.  I think you’ll find that it doesn’t address the truss span.

On earlier sheets addressing the truss spans you’ll find the dimension from chord to chord given explicitly.

T-P Bridge Visit–Required Work

Question

I am a little confused as to which problems I should be doing.  I am going off of the Excel spreadsheet, but noticing that there are also questions in the word document titled "T-P Lab Description", also on the blog it says to use a certain length for question 7 but on the ecel sheet there is no question 7, only on the word document. 

Response

You are to complete the Excel spreadsheet as in prior labs. A separate Word document is not necessary.  The tabs in that spreadsheet correspond to the questions in the ‘instructions’ document, but some questions in the ‘instructions’ document aren’t necessary since we’ve addressed them or provided the information. 

Be sure to complete the memo in the spreadsheet,

T-P Bridge Lab–Information Sources

Question

I am having difficulty finding in the plans the relevant information for making the needed calculations (the sketches needed to solve questions 1 and 4). Could you assist me with this?

 

Response

The document Tacony-Palmyra Drawings.pdf contains the necessary information on the construction of the top chord as illustrated in T-P Lab Description.docx.

• You’ll find it in about the middle of the drawings
• Note that the PA and NJ sides are symmetrical so detailed info is provided for one side only

A separate post provides the location of the strain gage.

T-P Bridge Visit–Additional Information

Mr. DeVitis provided us the following information after the visit.
The sensors were installed on the top chord of the first truss span 82' away from the support. So in the figure in question 7 of the assignment, L = 82''

Note that the support point mentioned is where the first truss on the Palmyra side abuts the bascule span.

10/18/2014 2PM - Corrected typo from 82" to 82'.  Also added note about support point.

Tacony-Palmyra Bridge Visit–Thursday 10/16

Next Thursday we’ll visit the Tacony-Palmyra Bridge. 

• The visit will take the entire lab period for each lab section
• We’ll be traveling by Drexel bus, walking across the bridge making observations and then returning to Drexel, all within the two hour lab period. 
• Below are the key facts for this visit.

Timing

• We will leave PMOMPTLY on the hour at the start of each lab - 10:00 and 12:00.  We really will leave on time.
• To ensure that the bus has sufficient capacity stick with your assigned lab section.
• We expect to be back by 11:50 and 1:50 respectively.  If there’s a traffic problem we could be delayed, but at that time of day it should be OK.

Location

• The bus will leave from in front of the main building on Chestnut street, probably on the south side of the street.
  • Sometimes for traffic reasons the bus goes to Market street.  If that’s the case we’ll alert you by having someone on Chestnut to direct you.  That person will leave Chestnut at 10:00 or 12:00
• If you’re a commuter you can meet us at the Tacony Palmyra bridge.
  • The easiest parking lot is on the NJ side
  • We’ll be starting our walk from the PA side so you’ll want to walk across the bridge to meet us.
  • We’ll probably start walking from the PA side about 10:25 or 12:25

Wearing Apparel

• Wear a windbreaker (raingear if the weather threatens)
  • The bridge is always markedly cooler and windier than on the ground
• Wear flat shoes – heels will be a problem on some of the sidewalks.

Safety

• The bridge is a dangerous place, particularly if you lean into the traffic lanes – it’s extraordinarily tight.
• LISTEN TO THE SAFETY INSTRUCTIONS WHEN WE’RE THERE

Tanker Collision with Bridge Lab–Questions

Question – About Q8 – Maximum Weight of Oil Tanker

A student visited me today perplexed about the method of calculating the maximum weight of the oil tanker in order not to exceed the allowable stress in the bridge pier – Question 8.

Response

A key thing to note is that in calculating the bending moment (Step 6 – slide 26,27) we’re pushing on the wall with Pyield.  Pyield is the point at the top of the linear elastic range (slide-16).  In essence, we’re ignoring what happens in the “plastic” region when addressing bending.

To work backwards to the allowable tanker mass/weight you need to check whether the maximum stress specified in the question occurs in the elastic range.  You can do this by comparing the moment that occurs with this stress in each pier leg to the maximum moment calculated in step 6.  If that moment is less then you can proceed assuming that you’re working exclusively in the elastic range – which simplifies the calculations.

Week-2 Lab–Geotech–Questions

Question

I am having trouble finding where the fill material is for the Geotechnical Engineering lab. I can clearly see the mud, gravel, and clay but I am not too sure where and what the fill material is.

 

Response

If you look on both sides of the drawing (Geotech Info) I believe you’ll find the labels for all the fill material.

Geotech Lab Questions

Question

If I am reading the new bridge diagram pdf correctly, question 1 relates to TP10 and questions 2 relates to PP6.  Question one asks us to calculate the pressure to -35 feet which is the extent of the support at TP10.  But question 2 asks us to calculate the force down to -65 feet when the support at that location only goes to roughly -20.  Am I interpreting this wrong?  Does the depth of the support not matter in terms of the vertical pressure at the point and depth?   And are approximate estimations for where one layer begins and the other ends acceptable?

Response

You are interpreting the locations correctly.

We ask you to calculate the pressure at a particular depth, not necessarily at the bottom of the support pier.

I’d note that at Location 2 we’re slightly below the bottom layer at –65’. 

• A reasonable way to interpret that last few feet is that it’s boring into rock, which would not add to the total pressure.  Only the water would act. 
• Another way is to assume that the drill rig stops at that layer and say that it cannot get to 65’

We’ll be lenient in how we evaluate student interpretions of those last few feet.