What it checks
The module designs a mat or raft foundation resting on a Winkler soil spring bed. It models the concrete slab using Mindlin 4-node plate elements tiled on a rectangular grid, with soil resistance represented by springs at the degrees of freedom. The design method follows ACI 318-19, utilizing factored loads for strength checks. The sequence of checks begins with solving the finite element model to determine displacement and contact pressure fields. The module then evaluates punching shear capacity at each column location and performs one-way flexure checks per unit width. These checks verify that the nominal capacities exceed the factored demands for both shear and bending moments.Inputs
- Geometry - Mat width in x and y directions (ft), number of elements in x and y, and mat thickness (in).
- Material Properties - Concrete compressive strength f'c (psi), reinforcement yield strength fy (ksi), concrete unit weight (pcf), and Poisson's ratio (typically 0.2).
- Reinforcement Details - Clear cover (in) and bar diameter for effective depth calculation (in).
- Soil Parameters - Winkler modulus ks (kip/in³), with typical values ranging from 0.025 to 0.500 k/in³.
- Column Loads - List of factored column loads including x and y coordinates (ft), factored axial load Pu (kips), and column dimensions cx and cy (in).
What it reports
- Displacement - Maximum downward displacement w_max (in) and minimum uplift displacement w_min (in).
- Soil Pressure - Maximum soil pressure q_max (ksf) calculated as ks times w_max, and an informational allowable bearing check against the ks input.
- Node Displacements - Per-node transverse displacement w (in) in row-major format for contour rendering.
- Punching Shear - Critical perimeter bo (in), effective depth d (in), factored shear demand Vu (kips), and nominal punching capacity φVn (kips) with φ=0.75.
- Flexure Demand - Maximum factored moment demand mu (kip·in/ft) per unit width.
- Reinforcement Area - Required As per foot (in²/ft), minimum As per ACI 318-19 §9.6.1.2 (in²/ft), and governing As (in²/ft).
Code references
The engine cites ACI 318-19 §22.2 and §9.6.1.2 for one-way flexure checks, and ACI 318-19 §22.6 for punching shear. The nominal punching capacity calculation references ACI 318-19 §21.2.1 for the strength reduction factor. The file header also lists AISC 360-22, though the specific checks described are concrete-based per ACI 318-19.