h b d t r r1 (cm 2 ) (kg/m) 5 50 37 4.5 7.0 7.0 3.50 6.93 5.44 6.3 63 40 4.8 7.5 7.5 3.75 8.444 6.63 8 80 43 5.0 8.0 8.0 4.0 10.24 8.04 10 100 48 5.3 8.5 8.5 4.25 12.74 10.00 12.6 126 53 5.5 9.0 9.0 4.5 15.69 12.37 14a 140 58 6.0 9.5 9.5 4.75 18.51 14.53 14b 140 60 8.0 9.5 9.5 4.75 21.31 16.73 16a 160 63 6.5 10.0 10.0 5.0 21.95 17.23 16 160 65 8.5 10.0 10.0 5.0 25.15 19.74 18a 180 68 7.0 10.5 10.5