AustraliaAS 3600:2018 (Amdt 2)
Beam reactions link to connected column and footing calculations automatically. Design rectangular concrete beams to AS 3600:2018 (Amdt 2) with unlimited spans; checks cover positive and negative flexural capacity, shear, and short- and long-term deflection.
Our rectangular concrete beam calculation allows analysis and design of a multi-span, multi-load beam to AS3600:2018.
Worked example
Simply supported and continuous RC beam worked examples
How to Design a Concrete Beam Using AS3600:2018 in Calcs.com from Calcs.com.
Method & scope
See the exact clause
Calculation method
The Concrete Beam calculator designs rectangular reinforced concrete beams to AS 3600:2018 (Amendment 2) using limit state design. A live FEA engine resolves internal forces for unlimited span and load configurations, and checks are performed for flexure, shear, and deflection at critical sections.Flexural capacity (AS 3600:2018, Cl 8.1)
Positive and negative moment capacities are computed using the rectangular stress block. For a singly reinforced section: phi × M_u = phi × A_st × f_sy × (d, gamma × k_u × d / 2) where gamma is the rectangular stress block depth factor (0.85, 0.007 × (f’c, 28) ≥ 0.67), k_u is the neutral axis parameter, and d is the effective depth. The strength reduction factor phi = 0.80 for bending per Cl 2.2.2. Minimum reinforcement (Cl 8.1.6.1) is enforced: A_st,min = 0.20 × (D/d)² × (f’ct,f / f_sy) × b_w × d where f’ct,f is the flexural tensile strength of concrete.Shear capacity (AS 3600:2018, Cl 8.2, simplified method)
The design shear strength without shear reinforcement (Cl 8.2.4.3): V_uc = beta_1 × beta_2 × beta_3 × b_v × d_v × sqrt(f’c) where beta_1 accounts for the shear span-to-depth ratio, beta_2 for axial force, and beta_3 for the depth effect. Where fitments are provided, the total design shear strength is: phi × V_u = phi × (V_uc + V_us) with V_us = (A_sv / s) × f_sy.f × d_v × cot(theta_v).Deflection checks (AS 3600:2018, Cl 8.5)
Three deflection limits are verified:- Short-term deflection: using the effective moment of inertia I_ef under short-term service loads
- Long-term deflection: adding a creep/shrinkage multiplier k_cs to the sustained-load deflection
- Imposed load deflection: deflection due to live load only, checked against the imposed deflection limit
Assumptions
No torsional demands are considered. Prestressing and post-tensioning are not included. Secondary effects on shear (V_uc) and load reversal are not considered. Beams are assumed to be enclosed within the building. Concrete detailing (bar laps, anchorage, hooks) is checked separately using AS 3600:2018 Cl 13.How to use it
1
Open the calculator
Open it from Run calc in the About this calculator panel above. To start from a typical setup, choose one of the presets listed there.
2
Enter your inputs
Work through the input sections from top to bottom. Click any input label to see its reference explanation, clause, conditions and assumptions. See Checks, References, Conditions and Assumptions.
3
Review the results and export
Check the utilization of each governing check in the summary, then export a PDF report. See Views and Export.
Rectangular concrete beam design to AS3600-2018 webinar & slides
The following webinar gives an overview of concrete beam design and worked examples using the Calcs.com concrete beam module ( Jump to 29 minutes for worked examples). Video:
Slides:
Designing a Concrete Beam Using the New AS3600:2018 - Webinar Slides - Calcs.com from Calcs.com
Available presets
Each preset opens the calculator with a typical setup already entered.Common questions
What design standard and method does this calculator use?
What design standard and method does this calculator use?
Limit state design to AS 3600:2018 (Amendment 2). Factored loads from AS 1170.0 load combinations are compared to design capacities for flexure and shear. Deflection checks use serviceability load combinations.
What are the key inputs?
What are the key inputs?
Key inputs are cross-section dimensions (breadth b_w and overall depth D, in mm), concrete compressive strength f’c, concrete weight class (normal or lightweight), reinforcement yield strength f_sy, clear cover, positive and negative longitudinal reinforcement (bar size and count), fitment (stirrup) size and spacing, span geometry, support conditions, and applied loads by type (dead, live, wind, etc.).
What checks does the calculator perform?
What checks does the calculator perform?
The calculator checks: positive moment capacity phi × M_u+ ≥ M* (AS 3600:2018 Cl 8.1), negative moment capacity phi × M_u- ≥ M* (Cl 8.1), shear capacity phi × V_u ≥ V* (Cl 8.2 simplified method), governing short-term deflection, governing long-term deflection (with creep factor k_cs), and imposed load deflection. Minimum reinforcement (Cl 8.1.6.1) is also enforced.
How is the effective moment of inertia calculated for deflection?
How is the effective moment of inertia calculated for deflection?
The cracked-section effective moment of inertia follows AS 3600:2018 Cl 8.5. The short-term deflection uses I_ef based on the cracking moment M_cr and applied moment M_s. Long-term deflection adds a time-dependent multiplier k_cs that accounts for creep and shrinkage under sustained loads.
What shear assumptions apply?
What shear assumptions apply?
Shear uses the simplified method (Cl 8.2.4.3), valid for f’c up to 65 MPa with no prestress, tension, or torsion. The maximum shear at supports is taken directly over or at any distance from the support, the Cl 8.2.3.2 reduction at a distance d_v from the support face is not applied.
How does load linking work with column and footing calculations?
How does load linking work with column and footing calculations?
Beam support reactions link directly to connected column and footing calculations in the same Calcs.com project. When any load or geometry changes in the beam, the downstream column and footing calculations update automatically, keeping the full gravity load path consistent without manual data transfer.
Next steps
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Calculate Concrete Development Length to AS 3600:2018
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Changes in AS3600:2018 Amendment 2 (Concrete)
Changes in AS3600:2018 Amendment 2 (Concrete)