Column Buckling in Frames: Understanding K Factors & Pcr

1. Rotational Spring stiffness K= 4EIb/Lb Pcr Pcr Pcr Idealized Model of Column Buckling in Frame Column Buckling in Frame Column buckling

2. Bracing Member Braced Frame Moment connection Unstable Frame Moment Resisting Frame

3. Pcr Pcr Pcr Pcr Columns in Braced Frames have 0< K  1.0 Buckling of columns in braced frames with pin connections at ends Buckling of columns in braced frames with moment connections at ends 0< K < 1.0 K = 1.0 Pcr Pcr Pcr Pcr Columns in Sway Frames have 1  K <  Buckling of columns in moment resisting frames with pin connections at one end Buckling of columns in moment resisting frames with moment connections at both ends 2.0  K 1.0  K  2.0

4. Pcr Pcr Buckling of Unbraced or Sway Frames Buckling of Braced Frames Substructure Substructure

6. 10 ft. W14 x 68 10 ft. W14 x 68 A Ky = 1.0 12 ft. W14 x 68 B 15 ft. W12 x 79 W12 x 79 W12 x 79 18 ft. 18 ft. 20 ft.

7. W14 x 74 12 ft. W14 x 74 A 15 ft. W12 x 79 W12 x 79 W12 x 79 B Kx = 2.0 18 ft. 18 ft. 18 ft. 18 ft. 20 ft. 20 ft. Best Case Scenario from Pg. 6-184