Advanced Concrete Section

Design reinforced, prestressed, and post-tensioned concrete cross-sections to AS 3600:2018 with biaxial interaction analysis, fire design, and moment-curvature analysis.

:::note[Design code scope — AS 3600 only at launch] ACS runs concrete design to AS 3600:2018 Amendment 2:2021, and that is the only design code selectable today. ACI 318-19 and EN 1992-1-1 are Coming Soon: both appear in the Materials panel’s design code list as disabled items and cannot be chosen for a new design. Everything on this site describing how ACS treats those codes is published ahead of them becoming selectable — read it as what is coming, not as what you can run today. :::

What is the Advanced Concrete Section tool?

The Advanced Concrete Section (ACS) is a cross-section design and analysis tool for reinforced, prestressed, and post-tensioned concrete members. It covers the full design workflow from defining geometry and placing reinforcement through to ultimate and serviceability limit state checks, fire rating verification, and PDF report generation.

ACS performs rigorous nonlinear analysis using fibre-based methods rather than simplified hand-calculation approximations. This means you get accurate results for non-rectangular sections, biaxial bending, complex reinforcement layouts, and elevated-temperature conditions that would be impractical to check by hand.

Capabilities

ACS supports the following analysis and design checks:

Ultimate limit state (ULS)

• Flexural capacity — uniaxial and biaxial bending with axial force, ductility verification
• N-M interaction diagrams — full uniaxial curves and 3D biaxial interaction surfaces
• Shear capacity — concrete and steel contributions per the code’s sectional shear model (AS 3600: simplified MCFT, Cl. 8.2.4)
• Batch design checks — run multiple load combinations and identify the governing case automatically

Serviceability limit state (SLS)

• Stress checks — verify concrete compressive and steel tensile stresses under service loads
• Crack width control — calculate characteristic crack width per code method
• Deflection parameters — effective moment of inertia, creep multipliers, long-term factors

Prestressing

• Prestress losses — elastic shortening, friction, draw-in, creep, shrinkage, and relaxation
• Transfer and service stresses — verify allowable stresses at jacking and long-term stages
• Ultimate capacity — prestressed section moment capacity with tendon stress increase

Fire design

• Heat transfer analysis — 2D finite element temperature distribution through the section
• Fire capacity — reduced material properties at elevated temperature, fire-rated interaction check
• Fire curves — ISO 834, ASTM E119, and Hydrocarbon fire curves

Advanced analysis

• Moment-curvature (M-$\kappa$) — full nonlinear load-deformation tracing from uncracked through cracking, yielding, and ultimate
• Multiple stress-strain models — Hognestad, Mander confined, Parabolic-rectangular EC2, Bilinear EC2, Kent-Park modified, Popovics/Thorenfeldt, and FIB MC2010 (the editor pre-selects the rectangular stress block for AS 3600 / ACI 318 simplified checks, and parabolic-rectangular for EN 1992-1-1). That pre-selection is a starting point in the UI, not a server-side fallback: the API refuses a request that omits stressModel rather than choosing one for you
• Time-dependent effects — age-adjusted effective modulus method (AEMM) for creep and shrinkage redistribution

Section geometry

• Parametric templates — rectangular, T-beam, L-beam, circular, hollow circular, box girder, I-beam, trapezoidal
• Custom geometry — draw arbitrary polygonal outlines with voids
• Reinforcement placement tools — individual bars, edge patterns, perimeter patterns, linear rows, circular rings, rectangular grids

Design standards

AS 3600 is selected from the materials panel, and all capacity calculations, reduction factors, ductility limits, and serviceability checks follow from it. The two Coming Soon codes are listed in the same panel but are not selectable; see Design standards for how ACS will treat each of them.

When to use ACS

Use ACS when you need to:

• Check the capacity of a reinforced or prestressed concrete section under combined actions
• Investigate biaxial bending capacity for columns or edge beams
• Verify fire resistance of a concrete member for a specified fire rating level (FRL)
• Explore the nonlinear response of a section through moment-curvature analysis

Next steps

• Getting started with ACS — create your first concrete section analysis
• Section geometry — define outlines, voids, and templates
• Reinforcement — place and manage reinforcement bars
• Prestressing — define tendons, compute losses, and check PT capacity
• Time-dependent effects — creep and shrinkage analysis