Parameters such as bearing capacity method, unit weight, soil type, adhesion & cohesion, passive pressure coefficient, soil to concrete friction etc. may be set here. If in App Settings, the values entered here will become the defaults for all subsequent new projects.
*Note: in previous versions of the products, the allowable bearing pressure and the foundation type (soil or pile supported) was set here. In the current version, the allowable bearing pressure and other allowable increases can be set in Allowables and foundation type can be set in Footing Geometry (if in Analysis Mode) or in Design Parameters (if in Design Mode).
Bearing Capacity Method:
The program uses the selected method to calculate the bearing pressure under the foundation base. The two different types of methods used by the program are
1. Linear Soil Pressure Method
2. Reduced Effective Area Method.
For a brief description of these methods, refer to the topic Soil Bearing Pressures.
When this option is selected, the percent of soil overburden indicated is neglected in calculating the soil overburden resulting in a lower gross bearing pressure value than if soil overburden is not neglected. This option may be used where gross bearing pressure and not net allowable bearing pressure value is available.
When this option is selected, the percent of specified soil cover above the top of the footing is neglected in calculating the stability ratio and sliding safety factor of the foundation for allowable load combinations. Full soil cover is considered for ultimate strength load combinations or concrete design regardless of the value of the percent neglected soil cover specified.
Enter coefficient of cohesion and/or coefficient of friction for a cohesive type soil and coefficient of adhesion and/or coefficient of passive resistance for a granular type soil. These values allow the program to calculate the lateral resistance of the soil. These values are used in determining the lateral resistance of soil to the applied lateral load for both unfactored and factored load combinations.
This field consists of soil sub types for cohesive or granular soils. This field is currently not used in the design of foundations in Foundation3D or Mat3D. However it is planned for use in future releases. The default value in this field if left as is or changing the value will not affect the foundation design in Foundation3D or Mat3D.
This item under Miscellaneous section provides an option to select whether or not sizable base be in compression and provide the percent in compression. By default the option is not selected.
If the maximum bearing to allowable bearing ratio of footing(s) must not exceed a certain value, enter a value less than 1 here. If any footings exceed this ratio, it will be highlighted for each load combination where this ratio is exceeded.
The buoyancy section allows considering buoyancy under the foundation. Specify the depth of water table below grade. A value of 0 for depth of water table below grade indicates that the water table is at grade. Buoyant forces are considered only if the water table is above the bottom of the footing.
The load factor to use in computing the stability under buoyant conditions can also be specified by using the "Do not use self weight factor in calculating buoyancy stability" option. By default, the program uses the self weight factor in computing the stability ratio under buoyant conditions. However if the self weight factor is less than 1 and a factor of 1.0 is desired, checking the option will compute the stability ratio based on a factor of 1.0 applied with the buoyant load under buoyant conditions.
A geotechnical engineer typically gives the value entered here. It is computed by applying a safety factor to the ultimate bearing pressure and represents NET ALLOWABLE bearing pressure on the soil. This value plus the overburden constitutes the gross allowable bearing pressure as indicated in the Bearing Capacity Tab displaying the bearing pressures on the soil.
Foundation Type:
The foundation type can be Soil-Supported or Pile-Supported.
In Analysis Mode, the foundation type can be set in Footing Geometry. When Pile-Supported foundation type is selected, a Pile Layout input field will appear in the Inputs section.
In Design Mode, the foundation type can be set in Design Parameters.
Angle of Internal Friction:
This value is used by Shaft3D. It is not used by Foundation3D and Mat3D. The sliding resistance calculated in Foundation3D and Mat3D uses the Passive Pressure Coefficient. Angle of internal friction is not used to determine the passive pressure coefficient.
Coefficient of Lateral Earth Pressure:
This value is used only in a tank ringwall workspace.
Allowable Settlement:
This setting is currently not used for any of the products. Its use is planned for a future release.
Frost Depth:
This setting is used only in a tank ringwall workspace.