C-23 The effective length factor (K) was introduced in page (C-7) for six ideal conditions, these are not encountered in practical field conditions. LRFD commentary provides both real conditions and standard ideal conditions (C-C2.2) (page to 242) Braced Frames: No lateral movement is allowed (0.5 < K < 1.0) (sideway prevented) Unbraced Frames: Lateral movement possible (1.0 < K < 20.0) (sideway allowed) a)Diagonal bracing b) Shear Walls (masonry, reinforcement concrete or steel plate)

C-24 * For fixed footing G = 1.0 * For pinned support G = 10.0 where A is top of column where B is bottom of column

C-25 In the rigid frame shown below, Determine K x for columns (AB) & (BC). Knowing that all columns webs are in the plane. Column (AB): Joint (A): Example C – 8 :- Solution: A B C W24 x 55 W24 x 68 W12 x 120 W12 x 96 12' 15' 12' 18' 20'

C-26 For joint B,:- From the alignment chart for sideways uninhibited, with G A = 0.94 and G B = 0.95, K x = 1.3 for column AB. Column (BC): For joint B, as before, G = 0.95 For joint C, at a pin connection the situation is analogous to that of a very stiff column attached to infinitely flexible girders – that is, girders of zero stiffness. The ratio of column stiffness to girder stiffness would therefore be infinite for a perfectly frictionless hinge. This end condition is only be approximated in practice, so the discussion accompanying the alignment chart recommends that G be taken as From the alignment chart with G A = 0.95 and G B = 10.0, K x = 1.85 for column BC.