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Soil Type
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Select the type of soil supporting the foundation
from the drop-down list:
-
Cohesive Soil
-
Cohesionless Soil
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| Pedestal Clear Cover
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Type a concrete clear cover distance to be used for
the pedestal, if present, in the selected units.
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Bottom Clear Cover
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Type a concrete clear cover distance to be used for
the bottom-most layer of footing reinforcement, in the selected units.
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Unit Weight of Soil
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Type a density to be used for the soil, in the
selected units.
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Soil Bearing Capacity
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Type the allowable bearing capacity of the soil, in
the selected units.
(US Codes only) If the
Use Variable Bearing Capacity option is
set in the
Global Settings dialog, then
select a bearing capacity table name from the drop-down list, instead.
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| Multiplier on Soil Bearing Capacity for Ultimate Loads
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This is used to specify a limit on soil pressure not to be
exceeded for ultimate load cases. This is multiplied by the
Soil Bearing Capacity value (used for
service load cases) to indicate the ultimate bearing capacity of the soil.
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|
Depth of Soil Above Footing / Footing Embedment
Depth
|
This field varies depending on the
Type of Depth selected:
- For
Fixed Top, type the depth from soil
surface to the top of footing, in the selected units.
- For
Fixed Bottom, type the depth from the
soil surface to the bottom of the footing, in the selected units.
Note: For tapered or stepped footing types used in Chinese isolated footings, the top of the footing is taken at the top of the taper or steps.
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Type of Depth
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Select the direction for incremental depth in design
from the drop-down list:
- Fixed Top – The top of
footing is fixed in this option, footing thickness is incremented
(if needed) downwards.
Type of depth: fixed top
-
Fixed Bottom – The bottom of footing is fixed
in this option, footing thickness is incremented (if needed)
upwards. Increase in Footing Thickness reduces soil depth.
Type of depth: fixed bottom
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|
Surcharge for Loading
|
Type a surcharge loading above the footing, in the
selected units.
For the stability check for calculating the factor of safety in sliding, surcharge is treated as a temporary load, meaning, it is treated as though there may be times when it is not present. Thus, its contribution to sliding resistance is not considered. That will reduce the total sliding resistance which will produce a more conservative result.
However, surcharge is considered when determining the soil bearing pressures under service loads since it leads to an increase in soil pressure.
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|
Depth of Water Table
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Type the depth from soil surface to the water table,
in the selected units.
If water table is not to be considered for this
footing, leave this value blank.
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Cohesion
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(Cohesive Soil type) Type a cohesion pressure, in the selected units.
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Shear Strength
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(Cohesionless Soil type) Type a shear strength for the soil, in the selected
units.
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Min % of Contact Area for Service Loads
|
Type a minimum percent of footing surface area that
must remain in contact with the supporting soil under service load
conditions. This is used to limit uplift or overturning. Type zero
(0) to direct the program to skip this check.
Note: If these
requirements are not met, footing design is reported as failure.
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|
Min % of Contact Area for Ultimate Loads
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Type a minimum percent of footing surface area that
must remain in contact with the supporting soil under ultimate load
conditions. This is used to limit uplift or overturning. Type zero
(0) to direct the program to skip this check.
When the
Design Type is selected as
Calculate Dimension on the Footing
Geometry page, the footing size will be calculated large enough to satisfy this
requirement.
The maximum soil pressure that is reached and the least
(smallest) area in contact from among all the ultimate load cases is reported
in the calculation sheet.
Note: If these requirements are not met, footing design is reported
as failure.
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Set as Default
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Select
Yes to have the current parameter values set
as the defaults for new Isolated Footing: Cover and Soil parameters.
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