Week-8 Rec Center - Lab Locations and Times

This week we’ll be touring the Rec Center AND having time in the lab to address the calculation assignment of the week.  You should plan to be involved the whole two hours of your lab period.

Note that we will meet outside the East entrance to the Papadakis Integrated Sciences Building (inside if raining).  Here’s a map showing where we’ll meet and where we’ll go.

Wear flat shoes (NOT heels) – we’ll walk on sensitive surfaces.

 

Time & Location

Lab	Last Name	Time	Location	2nd Hour
060	A-Kelly	10:00	Papadakis ISB	Randell-121
060	Kerr-Z	10:00	Randell-121	Papadakis ISB
061	A-K	12:00	Papadakis ISB	Randell-121
061	L-Z	12:00	Randell-121	Papadakis ISB

Bridge Lab–Solution Steps Suggestion

A number of students have asked for more instructions on the method to address the Tacony-Palmyra bridge lab prepared by Dr. Moon.  Neha Sunger, one of our TA’s, has most kindly prepared the following notes.

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1) Look at the “Truss Spans Stress Sheet” drawing at pg-12 of Tacony-Palmyra Drawings document.

a. There are 3 “truss span” sketches and two “cross-section” sketches.

b. Look at the third sketch from top and locate pier F.

c. Locate the position of strain gauges. They are 85’ east of pier F on the New Jersey Truss span.

i. For this, roughly estimate the 85’ distance from pier F to pier G (shown that the total distance between two piers is 244.87’).

d. Submit a sketch showing this location (You can copy –paste the given drawing and mark the location on it OR you can draw it yourself but make sure to label beams and spans appropriately).

e. Look the second sketch from top on the same page and find the details of the members of the top truss chord at the gauge location.

f. Submit a sketch of the cross-sectional view of the top chord highlighting the cover plates, angles, webs and plates. (A sample of this sketch is provided by Dr Mitchell, check the blog post at- http://caee-201ay121.blogspot.com/2012/10/top-chord-tacony-palmyra-bridge.html).

2) Calculate the cross-sectional area of the top chord following the example calculation given in the “T-P Lab description 20121018.docx” document.

3) Now calculate the top chord force using the following expression:

F = ε E A

Where,

F = force in the top chord (lb)

ε = maximum measure strain (in/in) (given in the excel sheet)

E = elastic modulus of steel (29,000,000 psi)

A = cross-sectional area of the top chord (calculated in step 3 above)

a. Value of ε should be the maximum strain recorded in the member.

i. Either identify the minimum strain gauge data reading for each sensor and take an average.

ii. Or pick any one strain gauge but justify the criteria for the selection.

b. BONUS: Answer to the question- Why are the maximum readings negative?

4) Check the truck picture and locate if it’s in lane 1, 2 or 3.

5) Assign a ‘distribution’ factor based on which lane the truck was in when it crossed the bridge.

γ = distribution factor:

0.75 for Lane 1

0.5 for Lane 2

0.25 for Lane 3

6) Now apply moment equilibrium (see the forces shown below in Figure 1) and calculate the weight of the truck using equation:

ΣM_o = 0

F (H) - γ W (L) = 0

W = [F (H)] / [γ (L)]

Where,

L= truss span (given 85’)

H= distance between chords (get from the pg-12 drawing)

F= calculated in step 4.

Fig. 1

Strain Gauge Location for Week-4 Lab

Question

“It is given that the strain gauge is located approximately at 35.0 [%] of the span of the bridge. I have checked the diagrams provided on bblearn, though I am still uncertain about which measurement this is. My question is: Is it 35 [%] of the linear distance, or, since the bridge has a parabolic like shape, is it 35 [%] of the generally parabolic distance? “

Response

This is an good question that made us realize we hadn’t shown you the strain gauge location on the bridge as we had intended – the result of the rain disruption last Friday.

John Devitis provided the following information that will help you, in conjunction with the drawings, to locate the place they are applied.

The strain gauges are located 85’ east of Pier F on the New Jersey Truss span.  You can ignore the information about the percent location since this is more precise.

Each member of the truss is straight so the overall shape of the bridge doesn’t matter.  For your purposes you can assume the truss member is horizontal (it’s close enough).

Tacony-Palmyra Bridge Visit – Friday 10/19/2012

This coming Friday 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.

Our Hosts

• Dr. Franklin Moon of our department has arranged the visit for us.  Some of his graduate students will join us and conduct tour groups.
• We are there through the courtesy of the Burlington County Bridge Commission, which owns the bridge.

Preparation

• Download and bring the appropriate materials from the Week-4 Lab assignment.
• Follow Dr. Moon’s instructions in his Wednesday lecture.

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