h b d t r r 1 (cm 2 ) (kg/m) 5 50 37 4.5 7 7 3.5 6.93 5.44 6.3 63 40 4.8 7.5 7.5 3.75 8.444 6.63 8 80 43 5 8 8 4 10.24 8.04 10 100 48 5.3 8.5 8.5 4.25 12.74 10 12.6 126 53 5.5 9 9 4.5 15.69 12.37 14a 140 58 6 9.5 9.5 4.75 18.51 14.53 14b 140 60 8 9.5 9.5 4.75 21.31 16.73 16a 160 63 6.5 10 10 5 21.95 17.23 16 160 65 8.5 10 10 5 25.15 19.74 18a 180 68 7 10.5 10.5 5.25 25.69 20.17 18 180 70 9 10.5 10