ARCHITECTURAL STRUCTURES: ORM, BEHAVIOR, AND DESIGN DR. ANNE NICHOLS Co-Ten Steel Sculptue By Richad Sea Museum of Moden At ot Woth, TX (AISC - Steel Stuctues of the Eveyday) SUMMER 2014 lectue seventeen steel constuction: columns & tension membes Steel Columns & Tension 1
Stuctual Steel standad olled shapes (W, C, L, T) tubing pipe built-up Steel Columns & Tension 2
Design Methods (evisited) know loads o lengths select section o load adequate fo stength and no buckling Steel Columns & Tension 3
Allowable Stess Design (ASD) AICS 9 th ed slendeness atio a fo kl/ C c f citical. S. Kl 12 23 2 E Kl 2 = 126.1 with y = 36 ksi = 107.0 with y = 50 ksi Steel Columns & Tension 4
C c and Eule s omula Kl/ < C c shot and stubby paabolic tansition Kl/ > C c Eule s elationship < 200 pefeed C c 2 2 E y Steel Columns & Tension 5
C c and Eule s omula Steel Columns & Tension 6
Shot / Intemediate L e / < C c whee a. S. 5 3 Kl 1 2C 2 c 3 2 y. S. Kl Kl 8C 8C 3 c c 3 Steel Columns & Tension 7
Unified Design limit states fo failue a n c 0. 90 n c A g u c n 1.yielding 2.buckling Kl Kl E 4. 71 o e e elastic buckling stess (Eule) y E 4. 71 o e y 0. 44 0. 44 y y Steel Columns & Tension 8
Unified Design n = c A g fo fo Kl Kl whee 4. 71 4. 71 e E y E y 2 E KL 2 c 0. 658 0. 877 c e y e y Steel Columns & Tension 9
ocedue fo Analysis 1. calculate KL/ biggest of KL/ with espect to x axes and y axis 2. find a o c fom appopiate equation tables ae available 3. compute allowable = a A o n = c A g o find f actual = /A 4. is allowable ( a n /)? o is u n? yes: ok no: insufficient capacity and no good Steel Columns & Tension 10
ocedue fo Design 1. guess a size (pick a section) 2. calculate KL/ biggest of KL/ with espect to x axes and y axis 3. find a o c fom appopiate equations o find a chat 4. compute allowable = a A (o n / = c A) o n = c A g o find f actual = /A Steel Columns & Tension 11
ocedue fo Design (cont d) 5. is allowable ( a n /)? o is u n? yes: ok no: pick a bigge section and go back to step 2. 6. check design efficiency pecentage of stess = if between 90-100%: good 100% if < 90%: pick a smalle section and go back to step 2. c Steel Columns & Tension 12
Column Chats, a (pg. 361-364) Steel Columns & Tension 13
Column Chats, c Steel Columns & Tension 14
Column Chats Steel Columns & Tension 15
Beam-Column Design moment magnification (-) M u B M 1 m a x f a c t o e d B 1 1 ( C u m / e1 ) C m modification facto fo end conditions Steel Columns & Tension 16 = 0.6 0.4(M 1 /M 2 ) o 0.85 estained, 1.00 unestained e1 Eule buckling stength e 1 2 EA Kl 2
Beam-Column Design LRD Steel fo 0. fo 2 c 0. 2 c : : u 8 M 9 bm M bm is equied load, c is capacity c M c - esistance facto fo compession = 0.9 M b - esistance facto fo bending = 0.9 n u 2 c n ux ux nx nx b M M b uy uy ny ny 1. 0 1. 0 Steel Columns & Tension 17
Design Steps Knowing Loads (evisited) 1. assume limiting stess buckling, axial stess, combined stess 2. solve fo, A o S 3. pick tial section 4. analyze stesses 5. section ok? 6. stop when section is ok Steel Columns & Tension 18
Rigid ame Design (evisited) columns in fames ends can be flexible stiffness affected by beams and column = EI/L G fo the joint EI EI l c is the column length of each column l b is the beam length of each beam measued cente to cente l l c b Steel Columns & Tension 19
Rigid ame Design (evisited) column effective length, k A B Steel Columns & Tension 20
Tension Membes steel membes can have holes educed aea A n A inceased stess g A of all holes t s 4g (AISC - Steel Stuctues of the Eveyday) Steel Columns & Tension 21
Effective Net Aea likely path to ip acoss bolts divide tansfeed foce too shea lag A e A n U Steel Columns & Tension 22
LRD - Tension Membes limit states fo failue 1. yielding t u n n 0. 90 y A g u t n 2. uptue* Steel Columns & Tension 23 A g - goss aea A e - effective net aea (holes 1/8 + d) t 0. 75 u = the tensile stength of the steel (ultimate) n u A e