Let me explain this with some values.
To get the Allowable drift to be L/40, you must have input the following command
PRINT STORY DRIFT 0.025
The drift factor (without the correction for Cd/I) which you picked up from the table, is 0.025. Now let us say Cd=3 and I=1.0. So Cd/I =3/1=3. Hence the adjusted drift factor =0.025/3= 0.0083
To account for the Cd/I, you should specify the command as
PRINT STORY DRIFT 0.0083
Now to answer your additional queries,
1. The different denominators like L/61, L/88, L/467 are the actual ratios of drift/story height at the various story levels. Since the drift amounts are different at different stories, the actual ratio values would change. For example let’s say the drift at a particular story is “d” cm. Let’s say your story height is L m. So the number in the denominator is obtained as L X 100/d . The number will change for each story depending on the drift value at each story and the story height.
2. Average displacement is the average of the displacements of all the nodes at a story level. Drift on the other hand is the relative displacement of a story with respect to the story underneath. For example as per your screenshot, at the 7th story, the average displacement in X is 6.8408 cm. To get the drift at story 7, you will have to subtract the average displacement in X for the story 6 ( which is 6.5807 cm ) from this value. So drift at story 7 in X = (6.8408 – 6.5807) cm = 0.2601 which is reported by STAAD.Pro as 0.2602 ( some rounding off causes a negligible difference )
I hope this explains.
