I thought and thought and can't se how the length of the bolt has anything to do with something hanging from the ceiling except for how close to the ceiling do want the hanging panel.
"I thought and thought and can't se how the length of the bolt has anything to do with something hanging from the ceiling except for how close to the ceiling do want the hanging panel."
The concern has to do with the method used to attach the bolts to the concrete. If you were to thread a bolt into steel, then the maximum strength would be attained by making the thread length approximately 1.5 times the nominal diameter of the bolt. If you had a 1/2" diameter bolt then the maximum strength would be realized with a 3/4" long threaded hole.
In this case, the material that was being threaded into was much weaker than steel and in order to attain the strength required to hold the panels in place, the area of engagement would need to be much greater.
Not knowing what the design parameters or requirements were, I can only speak in generalities. If the strength of the base material were to be 10% of the strength of steel, then the length of engagement to attain the strenght of a steel base would be 10 times that required in steel. In other words, if peanut butter had 1/100 of the strength of steel, then you would have to put our 1/2" bolt into 75" of peanut butter in order to match the strength of a tapped hole in steel.
In this case, they were only trying to insure that the mounting strength of the bolt that was epoxyed into concrete was adequate (with an appropriate safety margin) to hold the panels in place assuming that the bolts were properly installed.
Whereas a 1/2" bolt installed in steel could fail with a load of perhaps 18,000 pounds. The same bolt epoxyed into concrete could fail at 1,200 pounds although the mode of failure would not be the same. In the first case, the bolt itself should be the weakest component whereas in the second, the interface between the bolt and the concrete would be the point of failure. Again I am simplifying, but the more epoxy that you have in contact with the bolt, the stronger the joint will be. Thus the deeper the bolt is imbedded into the concrete, the stronger the joint wil be.
With the technology used in this application however (an epoxy joint), it is impractical to get much more than 10% of the strength of a steel to steel joint. Moreover if the installation is improperly made, the theoretical strength goes out the window.
This example uses SWAGed numbers (Scientific Wild Assed Guess) and I make no claim as to their accuracy other than to say they are close enough for illustration.