Foundation Design Software: Spread, Combined, and Strap Footings

A spread footing is an element that spreads the loads in such a way that the soil bearing pressures are under the allowable limits. ASDIP FOUNDATION design software computes soil bearing pressures induced by a square or rectangular spread concrete footing subject to vertical load and biaxial moment. This structural engineering software analyzes the footing stability for overturning, sliding, and uplift. The software performs concrete footings design based upon Ultimate Strength Design Method within ACI 318. Load combinations occur per ASCE 7. Columns may be eccentric in two directions.

The footing is assumed to be perfectly rigid with constant thickness and rotates about its mass center to maintain equilibrium of forces. ASDIP FOUNDATION can calculate the soil pressures under the footing with any service load combination including uplift loading. The pressures may also be calculated when only a part of the footing is in contact with soil (partial bearing). This is especially useful when a footing with small vertical load and big moments is being designed, such as a footing at the corner of a building under lateral loads.

Input

The input options are straightforward and logically presented in tabbed pages. The required input data includes the footing and column dimensions, material properties, allowable soil bearing pressure, and acting service and factored loads. In addition, the software accepts a number of load cases, such as dead, live, snow, wind, and seismic to be combined internally. Modeling a single set of pre-combined loads is also possible.

Output

The program checks the footing stability in overturning, sliding and uplift for the service combined loads, and performs the concrete footings design, which includes the one-way shear, punching shear and bending for the factored combined loads. In each case the controlling load combination is identified and reported.

In case of partial bearing, the software accurately calculates the bearing pressure distribution on the base of the footing. The one-way shear, the punching shear, and the bending moments are calculated based on the bearing pressures under the factored loads. The program uses a sophisticated algorithm based on integrals to find the areas, volumes, and centroids of these irregular resulting geometric shapes.

A detailed step-by-step report is available to the touch of a tab, which is updated with every new change. In addition, ASDIP FOUNDATION uses a pre-formated colorful text-with-values output for easier identification of the problem areas. ASDIP FOUNDATION generates a graphical view of the designed footing and the resulting pressures and forces. The program also generates the moment and the shear plan views for the controlling combination, as well as a view of the construction section and elevation with the reinforcement information.

A combined footing is one that usually supports two columns. If a property line exists at or near the edge of an exterior column, an isolated footing would be placed eccentrically under this column and it would tend to tilt. Overturning of the exterior footing is prevented by supporting the two columns on a common footing.

The use of a combined footing may be justifiable under conditions where the distance between columns is short and the stability of an exterior isolated footing would be compromised. It is common practice to size the combined footing so that the resulting soil bearing pressure is uniform. To accomplish this, the footing shape is sometimes trapezoidal or rectangular, depending on the loads. A combined footing is usually analyzed as a beam in the longitudinal direction and as a footing in the transverse direction.

This foundation design software computes the soil bearing pressures induced by a cantilever footing under the action of vertical loads and bending moments, per the latest ACI design criteria. It designs the reinforcing steel, and checks the one-way and two-way shear stresses. In addition, the program generates the shear force and bending moment diagrams in order to design the reinforcement in the longitudinal direction. The concrete footings design is based on the Ultimate Strength Design Method of the ACI 318. Load combinations per the ASCE 7.

Input

The input options are conveniently designed in tabbed pages. The required input data includes the footing and columns dimensions, the material properties, the allowable soil bearing pressure, and the acting service and factored loads. In addition, the program accepts a number of load cases, such as dead, live, snow, wind and seismic, to be combined internally. Alternatively, you can input a set of pre-combined loads.

Output

This software checks the footing stability in overturning, sliding and uplift under the service combined loads, and performs the concrete footings design, which includes the one-way shear, punching shear and bending under the factored combined loads. In each case the controlling load combination is identified and reported.

For a quick overview of the design results click the “At a Glance” tab. A more detailed step-by-step calculations are available at the “Detailed” tab, which is updated with every new change. In addition, This foundation design software uses a pre-formated colorful text-with-values output for easier identification of the problem areas. Use the Print Preview command to see a preview of the pre-formatted report on-screen, which includes the color graphics generated by the software.

ASDIP Foundation generates a graphical view of the footing design and the resulting pressures and forces, as shown. The program also generates the moment and the shear diagrams for the controlling combination, as well as a view of the construction section and elevation with the reinforcement information.