Class Activity A 12 ft long C12x207 A992 section is used as

Class Activity A 12 ft long C12x20.7 A992 section is used as a compression member. Both ends can be considered flexurally and torsionally pinned. To strengthen the section for flexural buckling about its weak axis a brace is provided at mid- length. Lateral brace 0) Determine clastic flexural buckling stres abut thesrong axis of the section. Answer F-293.3 ksi (ii) Determine elastic flexural buckling stress about the weak axis of the section. Answer: Fey-35.07 ksi (iii) Determine elastic torsional buckling stress of the section. Answer: Fez-3842 ksi (iv) Determine the combined flexural-torsional buckling stress. Use the general formula. Answer: Fe 35.07 ksi

Solution

i) effective length of column about strong axis=12 ft

radius of gyration about strong axis=4.6 in

slenderness ratio=12*12/4.6=31.3

buckling stress = pi²*29000/31.3²=292.07 ksi

ii)effective length of column about strong axis=12/2=6 ft

radius of gyration about strong axis=0.8 in

slenderness ratio=6*12/0.8=90

buckling stress = pi²*29000/90²=35.33 ksi