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.