Reinforced concrete (ACI 318-19)
The Concrete class in New (Alt+N) designs a rectangular tied column under biaxial axial load and bending, or a beam in flexure, shear and torsion. Like Member design, the interface only shows what applies: no bolts, welds, FE or fabrication.
Input#
- Section: width b, depth h and the unsupported length (column) or span (beam).
- Material: f'c, fy, fyt, λ and maximum aggregate size.
- Bars: for a column, bars per face along b and along h (corners included) and the bar size; for a beam, bottom and top bars and the support condition (Table 9.3.1.1).
- Ties / stirrups: size, spacing, legs parallel to h and to b, and clear cover.
- Slenderness (column): nonsway or sway, k for each axis, M1/M2 (negative in single curvature) and βdns.
Load cases: P (+ compression), Mx, My, Vy, Vx and T.
Checks#
| Check | Reference |
|---|---|
| Biaxial P–M: Mu/φMn at the case's Pu, in the direction of the moment | 22.2, 22.4, 21.2.2 |
| Axial limit φPn,max = 0.80·φPo | 22.4.2.1 |
| Slenderness and moment magnification (nonsway frames) | 6.2.5, 6.6.4 |
| Beam φMn (positive and negative), As,min and εt ≥ 0.004 | 22.2, 9.6.1.2, 9.3.3.1 |
| Shear in each direction and biaxial interaction | 22.5, 22.5.1.11 |
| Torsion: threshold, section limit, At/s and Al | 22.7 |
| Detailing: reinforcement ratio, tie size and spacing, bar spacing, crack control | 10.6, 25.7.2, 25.2, 24.3.2 |
| Minimum beam depth (deflections) | Table 9.3.1.1 |
Diagrams#
Diagrams opens a panel to the right of the model with the 3D interaction surface (φPn, φMnx, φMny): every load case is a point colored by its status, the selected case's Pu cut is drawn as a ring and the φPn,max cap in red. Drag to rotate, scroll to zoom, or jump to the 3D, P–Mx, P–My and Mx–My views. Below it, the P–M diagram in the direction of the selected case's moment and the Mx–My contour at its Pu. For beams, a table lists the flexural capacities against the demands.
Verification#
The engine matches spColumn within 0.6% on StructurePoint's 16×16 in Grade 80 column (control points) and reproduces the 16×20 in biaxial example (Pn 425.4 kip, Mnx 321.4, Mny 200.8 kip-ft).
Not yet included#
Circular and spiral columns, walls with boundary elements, slabs and footings, multiple bar layers, development lengths, computed deflections, sway frames and Chapter 18 seismic design.