Neutral axis vs microstrain plot

[chinti]

hi, i got a list of data containing strain for four different strain gauge, lb, and time elapsed. is there anyway i can calculate the distance from bottom of a girder using the given data to plot something like this? i have also been given the neutral axis for each strain gauge.

 

[paisiello2]

Why is a strain gauge measured in "lb"?

What is a neutral axis for a strain gauge?