Strength Table -        other strength abilities
13 or less: normal      normal
14       -/-            as 14 str
15      +0/+1           as 16 str
16      +1/+2           as 18 str
17      +2/+3*          as 18/51-75
18      +2/+4*          as 18/76-90
19      +3/+6           normal 
20      +3/+8           normal
21+     as normal       normal

*may only get better than +1/+2 by choosing exceptional strength

The "great strength" ability no longer exists.