ACI 318-02 Strength Reduction Factors for columns
ACI 318-02 Strength Reduction Factors for columns
(OP)
For members subjected to axial compression and bending, in the transition zone the code allows a linear variation of the phi value from .70 or .65 to .90 .However I am unclear on one point. If I use the equations under Fig R9.3.2 at what point can I begin the transition? It appears that you can start from the balanced point and vary it right up to .90. In the old code you had to compare Pn with with .10F'cAg or Pb and would start varying it after the lower of those two values. Am i correct that there is no longer a limiting point at which to start? thanks






RE: ACI 318-02 Strength Reduction Factors for columns
RE: ACI 318-02 Strength Reduction Factors for columns
RE: ACI 318-02 Strength Reduction Factors for columns
RE: ACI 318-02 Strength Reduction Factors for columns
RE: ACI 318-02 Strength Reduction Factors for columns
RE: ACI 318-02 Strength Reduction Factors for columns
Developing spreadsheet you must be running strain compatibility analysis that will show strains in all the reinforcing bars. Resistance factor is a function of maximum strain in rebar and has a Z-shaped diagram. Simly interpolate:
IF MaxStrain <= 0.002 THEN phi = phi_cmp (0.7)
IF MaxStrain >= 0.005 THEN phi = phi_bend (0.9)
IF 0.002<MaxStrain<0.005 THEN phi = phi_cmp + (phi_bend-phi_cmp)*(MaxStrain - 0.002)/(0.005-0.002)
For implementation see my spreadsheet ShortCol at www.yakpol.net
Hope it helps!
RE: ACI 318-02 Strength Reduction Factors for columns
RE: ACI 318-02 Strength Reduction Factors for columns
The theory stays the same for both codes, the only difference is the resistance factor. I compared my spreadsheet with PCACOL (99 code), and it was right on the money.
RE: ACI 318-02 Strength Reduction Factors for columns