Designing a Strip Foundation

Using the Finite Element Analysis and Concrete Beam Design

This guide explains how to model and design a strip foundation in MasterSeries, using MasterFrame and the Finite Element Analysis (FEA) module with the Concrete Beam Design module.

The method treats the foundation as an FE surface (slab) supported by vertical soil springs (subgrade modulus), with an attached concrete beam along the strip centreline for reinforcement design and scheduling.

Overview of the Approach

The FE surface represents the soil–structure interaction and carries the stiffness for the analysis.

• The attached beam represents the reinforced concrete section of the strip footing and is used for reinforcement design.

• To avoid double counting stiffness or self-weight, the attached beam is assigned zero stiffness (E = 0, G = 0) and zero self-weight.

Create the FE Surface and Apply Soil Stiffness

Model the Foundation Outline

1. Draw the boundary members representing the strip foundation outline.

2. Define the FE surface to be 1.0 m wide, centred on the column line.

3. Go to Create → Add Slab, Wall, Ramp (FE Surface).

4. Use Auto Select Main Border Members to select the boundary — it must form a planar, closed shape.

5. 1. Select the inner border members under the opening tab, so as to form a strip 

Define Material and Thickness

In the Material/Thickness tab:

• Select Codified Materials → Concrete (e.g. C28/35).

• Enter the slab thickness (e.g. 500 mm).

Define Supports (Subgrade Modulus)

1. Open the Edge/Support Conditions tab.

2. Apply a full-area Vertical Spring Support to the FE surface to model the supporting soil.

3. Input the subgrade modulus (e.g. 12,000 kN/m³) and set it as Compression Only.

Lateral Stability

Because no soil friction is assumed for a ground-bearing foundation, you must apply lateral restraints manually Select Nodal Supports from the restraint tab

• Apply X and Z restraints at one corner node.

• Apply either X or Z restraint at a second corner.

  This prevents rigid body movement without over-restraining the slab.

  For details, see 📄 Edge Restraints and Releases.

In this example, the columns are assumed to be tied into a surrounding ground floor slab (not modelled), so X and Z restraints can be applied at the column bases. The strip foundation then resists only vertical reactions.

Define the Attached Ground Beam

Create the Beam

The attached beam represents the reinforced concrete section of the strip footing and is used for reinforcement design only, it is assigned zero stiffness (E = 0, G = 0) and zero self-weight.. The FE surface carries the stiffness for the analysis.

Go to Create → Add Members (General).

Select Concrete Section and edit the section size to match the FE Surface geometry.

In the Section Properties, set:

• E = 0, G = 0 → ignored in analysis (shell element only).

• Zero Self Weight.

• Axial Release → optional, if only flexural effects are to be designed.

Place this beam along the centreline of the FE surface.

You can also define these settings later under 📄 Member Sections and Materials.

Define Attached Beams and Combined Results

Attach the Beam to the FE Surface

Open the FE Surfaces → Attached Beams tab.

Select the perimeter or centreline member to attach — it will highlight in red.

Combine Results and Define Flange Width

• Enable Use Combined Beam–Plate Results to include both the FE surface and beam effects.

• Define the flange width on each side (e.g. 500 mm + 500 mm = 1.0 m total).

  This ensures the design reflects the total effective strip width.

Apply Loads

Integrated Loading

• The FE surface automatically receives loads transferred from any attached elements (e.g. columns).

Member Loads

• You can apply Member Loads directly to the attached beam — they act compositely with the FE surface.
  

FE Surface Loads

• Apply Area, Line, Patch, or Point Loads directly in the FE Editor → Loading tab.

• Examples:

  • Point Loads for column reactions.

  • Line Loads for wall loads or edge pressures.

Self-Weight

• The slab self-weight is automatically included if the FE surface density is defined.

  • Typically assigned to Load Group D0 (Dead Load).

  • Confirm self-weight inclusion in your load cases and combinations.

Analysis

Run the FE analysis and review graphical results (bending moments, shear, and deflections).

Verify that the foundation behaves as expected — continuous load transfer, smooth moment profiles, and realistic soil pressure distribution.

Design

Export the FE results to the Concrete Beam Design module.

• Design and schedule reinforcement for bending and shear along the attached beam.

• The FE surface provides the correct structural actions, while the attached beam defines the physical concrete section for design and detailing.

Result

You now have a fully modelled strip foundation supported by soil springs, incorporating realistic soil–structure interaction and a concrete beam element for reinforcement design, all within the MasterSeries FEA workflow.