Design or Characteristic capacity of shallow foundations
KawanaReeves opened this issue · 3 comments
I was wondering whether the results for vertical and sliding capacity of the shallowfoundation function verticalcapacity_(un)drained_api are Design or characteristic Values? The docstrings suggest a design value, but I dont see the partial safety factors gamma_m as mentioned in the API reference document. So far safety factors are only used for the calculate_envelope function.
The values for the individual functions are characteristic values. You can apply factors by creating a ShallowFoundationCapacityUndrained or ShallowFoundationCapacityDrained object and applying the method calculate_envelope. This method has arguments factor_sliding=1.5 and factor_bearing=2.
Here's an example with factors for bearing and sliding increased to 3 and 2 respectively.
from groundhog.shallowfoundations.capacity import ShallowFoundationCapacityUndrained
analysis = ShallowFoundationCapacityUndrained(title='Undrained capacity')
analysis.set_geometry(length=8, width=5, depth=0, skirted=False)
analysis.set_soilparameters_undrained(unit_weight=15, su_base=10, su_increase=1)
analysis.set_eccentricity(eccentricity_width=0, eccentricity_length=0)
analysis.calculate_envelope(factor_bearing=3, factor_sliding=2)
plot = analysis.plot_envelope()
yeah I figured the calculate_envelope function uses the safety factors. I was just wondering, since the formula for capacity suggests a design value but the actual calculation omits the safety factors. I wasn't sure if groundhog, somewhere in the background, already implicitly transforms the characteristic values into design ones.
It's clear now. Thanks for your super fast reply. Much appreciated.
groundhog never does something implicitly 😉. The goal of the package is to reveal all the steps, either through the docs or at the very least through the open-source code.
You can of course use the function with factored material parameters but the API/ISO standard suggests using factors on the calculated resistances (vertical and horizontal).
The current approach allows flexibility in where you want to apply the factors.