Lab-3 Question-6 (revised)

Question:

“I am confused about Question 6 in Lab 3. When performing the back calculations, how is the value for Stage 2 deflection determined? Since, the equation is x Stage 2=(KE-PE)/P and KE is unknown, I do not see how it can be calculated. Should I use the same value I came up with in Question 2? Do I assume we don't want any Stage 2 deflection and use 0?”

Response from Prof. Dasaro

“I wanted the students to think a little.   That's why I did this” after a set of calculations that essentially recreate the lecture example.

He advises that you consider in what “region” of the stress-strain curve this stress in the pier would be located.  That will tell you something about whether you need to know the KE or not.

You’ll still need to think about what steps you need to take, but hopefully this hint will enable you to do so.

10/11/2011 07:40AM Addition from Prof. Dasaro

"Question 5 yields the bending stress in the bridge pier at the onset of unrestrained plastic flow. Compare this stress value against the 3,000 psi limitation in question 6."