| Design Method group |
| Setting | Description |
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| Spread Footings |
The design method is used to define the various methods that can be used for defining the footing design.
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Design Footing based on applied forces
- Select Optimum footing design for each column - This option designs each footing based on its loading. This method will give the most economical results but will also give the largest number of unique results.
- For footing of equal dimensions, select one footing design based on controlling steel - This option will give the same Reinforcement for all footings of similar dimension. The program will design all the footings then go through and find the controlling reinforcement for each unique footing size. This method will give less economical design results with the smallest number of unique footing designs.
- Design footing based on soil capacity - This option will check the soil capacity for each footing using the provided soil load combinations, but will then assume that the footing is fully stressed for the design of the concrete and reinforcement in the footing. This method will be the least economical method with a reduced set of unique footing designs.
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| Pile Cap Footings |
Select the method of pile cap design:
- Design Pile Cap Based on Pile Load - This option uses the pile forces for each load combination to check the pile cap design.
- Design Pile Cap Based on Pile Capacity - This option designs pile caps based on pile capacity. The beam shear, pile two-way shear, column two-way shear, and flexural design are based on the factored pile capacity. The load factors are calculated by taking the ratio of the factored and unfactored column axial force (similar to spread footing design based on soil capacity).
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| Design Options group |
The Design options are used to set global design parameters to better model the foundation. | Setting | Description |
|---|
| Include Moment Due to Shear for |
Spread, Continuous and Pile Cap footings - These options when unchecked, removes the shear in the columns, braces and walls supported on the foundation. In certain cases the engineer has provided another mechanism to resist the shear in the supported members and therefor needs to remove it from the foundation design. For Pile Caps ignoring the moment due to shear from the column will also ignore the shear resisted by the piles. |
| Include Spread Footing Self-Weight When Checking Soil Stress |
It is common to have soil reports state that the soil capacity includes the footing self-weight, in which case the engineer may want to deselect this option which will ignore the footing self-weight when the program checks the soil stress. The engineer must understand that ignoring the footing self-weight for footings with moments from the supported member will produce a less accurate soil stress due to the missing self-weight that would normally counter the moment. A better solution is to get the actual soil capacity without regard for the footing self-weight. |
| Keep Spread Footings Square During Optimization |
This option is used to force spread footings to be optimized square plan dimensions as long as the maximum dimension is any direction is not reached. |
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| Increase Spread Footing Size to Prevent Uplift in Concrete Load Combinations |
When the program optimizes on the size of Spread footings, it will increase the size of the footing if necessary so that there is no net uplift when considering the Soil Load Combinations (with a factor of Safety against uplift as explained in Section 8.2). In previous versions the program also increased the footing size if necessary to prevent uplift when considering the Concrete Load Combinations; this has now been made an option. When the option is selected the footing size is increased so that all the concrete load combinations produce a net compressive force on the soil. In other words at least one part of the footing is in contact with the soil for all load cases. This is consistent with the way the model was analyzed in RAM Frame where columns are assumed to remain attached to the base (i.e., they are assumed not to lift up from the ground in uplift).
When the option is deselected, the footing size is not increased to counter the uplift from the column axial load in concrete load combinations as long as the supported column does not have any moment on it. For a given concrete load combination that produce a net uplift on the footing, the footing is then designed to only resist the factored self weight and surcharge on the critical sections. This will produce flexural reinforcement in the top of the footing. It is important, therefore, for the engineer to ensure that combinations that do not produce uplift are also considered, even when there are some combinations that induce uplift.
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| Design Continuous Footings as Beams... |
(ACI 318 Design only) This option provides a way to design continuous footings as beams if they meet the user defined footing width to depth ratio. The program will automatically select the beam or footing design method during the optimization process. When the footing is designed as a beam the transverse reinforcement for the footing will not be designed and the ACI 318 beam flexure and shear criteria will be used for the design. |
