1. Purlin DIY Problem #1 Find M y, M cr, M crd and M cre for 72” centerline dimensions h = 7.507 in. b = 1.889 in. d = 0.795 in. r = 0.217 in. t = 0.059 in. properties E = 29500 ksi = 0.3 G = 11346 ksi f y = 55 ksi

7. DSM for Purlin DIY Problem #1

11. Test 8.5Z092 Local buckling testDistortional buckling test Test 8C043 Local buckling testDistortional buckling test 99% of NAS83% of NAS 106% of NAS90% of NAS Δ P Δ P Remember Distortional Buckling Gotcha! - comparison of two series of tests

12. Review DB in AISI Specification Distortional buckling provisions are integral to the Direct Strength Method of Appendix 1 The main Specification now has distortional buckling provisions as well, see Ballot 227B 227B Spec.227B Comm.

13. Distortional Buckling Commentary “Testing on 8 and 9.5 in. (203 and 241 mm) deep Z- sections with a thickness between 0.069 (1.75 mm) and 0.118 in. (3.00 mm), through-fastened 12 in. (205 mm) o.c., to a 36 in. (914 mm) wide, 1 in. (25.4 mm) and 1.5 in. (38.1 mm) high steel panels, with up to 6 in. (152 mm) of blanket insulation between the panel and the Z- section, results in a k  between 0.15 to 0.44 kip- in./rad./in. (0.667 to 1.96 kN-mm/rad./mm) (MRI 1981).”

14. Purlin DIY Problem #1 with spring Find M y, M cr, M crd and M cre for 72” with k  =0.15 kip-in/rad/in centerline dimensions h = 7.507 in. b = 1.889 in. d = 0.795 in. r = 0.217 in. t = 0.059 in. properties E = 29500 ksi = 0.3 G = 11346 ksi f y = 55 ksi