| Product(s): | SACS |
| Version(s): | All |
| Area: | PSI |
SACS PSI input file has T factor in PLGRUP line and in SOIL TZAPI line. Are they same or different? How is the factor calculated?
For the T factor in SOIL TZAPI HEAD, it is the T-Z curve calculated according to the API specification for the soil parameters we input, and then T is scaled according to the factor provided by user.
T factor in PLGRUP scales the T value on the user defined T-Z curve of the pile segment. This affects only on the pile you input your T factor for.
The factors are calculated to scale the SACS input data with respect to geotechnical report data. Many a times, users have a set of geotechnical data for T-Z, Q-Z and P-Y in such unit which are not in line with the SACS available units. Also, sometimes, the geotechnical data contains reference pile diameter, which in actual design case gets changed.
For example, let us assume, the geotechnical data has pile diameter (considered as reference dia or Rd) 72” and later during the engineering design, the revised diameter of pile became 84” (considered as actual dia of Ad). Then the diameter correction ratio is given by Ad/Rd = 84/72.
Now let us walk through the calculations of the factors as below, by providing different sets of user inputs and corresponding SACS inputs as sample demonstration:
1.T-Z Curve:
T Factor calculation:
Unit of T value provided in soil report, say is in MN/m.
Unit of T value required in SACS input is kN/cm2.
MN/m to kN/cm conversion factor = 1000/100 = 10
Rd = 72” = 72*2.54 = 183 cm
Hence, T factor for SACS = 10/π*Rd = 10/(3.14*183) = 0.017.
Z Factor calculation:
Unit of Z value provided in soil report, say is in mm.
Unit of Z value required in SACS input is cm.
mm to cm conversion factor = 1/10.
diameter correction factor = 84/72.
Hence, Z factor for SACS = 1/10*84/72 = 10/(3.14*183) = 0.117.
2. Q-Z Curve:
Q Factor calculation:
Unit of Q value provided in soil report, say is in MN.
Unit of Q value required in SACS input is kN/cm2.
MN to kN conversion factor = 1000
Rd = 72” = 72*2.54 = 183 cm
Hence, Q factor for SACS = 1000/(π/4*Rd^2) = 1000/(3.14/4*183^2) = 0.038.
Z Factor calculation:
Unit of Z value provided in soil report say is in mm.
Unit of Z value required in SACS input is cm.
mm to cm conversion factor = 1/10
diameter correction factor = 84/72
Hence, Z factor for SACS = 1/10*84/72 = 10/(3.14*183) = 0.117.
3. P-Y Curve:
P Factor calculation:
Unit of P value provided in soil report, say is in MN/m.
Unit of P value required in SACS input is kN/cm.
MN/m to kN/cm conversion factor = 1000/100 = 10.
Hence, P factor for SACS = 10
Y Factor calculation:
Unit of Y value provided in soil report, say is in mm.
Unit of Y value required in SACS input is cm.
mm to cm conversion factor = 1/10.
Hence, Y factor for SACS = 1/10 = 0.1.