Concrete Creep Calculation According to AS 3600 (Step-by-Step Guide)

Concrete creep is the time-dependent deformation of concrete under sustained load. According to the Australian Standard AS 3600, creep must be considered in structural design to ensure long-term performance, serviceability, and safety of concrete structures.

Creep affects:

  • Deflection of beams and slabs
  • Stress redistribution
  • Long-term structural behaviour

This guide explains how to calculate creep using a step-by-step method based on AS 3600.

Step 1: Basic Creep Coefficient (φcc,b)

The basic creep coefficient is obtained from Table 3.1.8.2 based on the compressive strength of concrete (f’c).

  • Lower strength concrete → Higher creep
  • Higher strength concrete → Lower creep

 Step 2: Time Development Factor (k₂)

The coefficient k₂ accounts for the effect of time and is calculated using:

  • Time (t) in days creep
  • Hypothetical thickness (th)

 Step 3: Age at Loading Factor (k₃)

The coefficient k₃ depends on the age of concrete at loading (τ):

  • Early loading → higher creep
  • Late loading → lower creep

 Step 4: Environmental Factor (k₄)                                                

Creep is influenced by environmental conditions:     

  • Arid → 0.70
  • Interior → 0.65
  • Temperate → 0.60
  • Coastal → 0.50

Dry environments increase creep

 Step 5: Strength Modification Factor (k₅)                                  

This factor accounts for high-strength concrete:

  • Normal strength → k₅ = 1.0
  • High strength → reduced creep

 Step : Stress Level Factor (k₆)                                                           

Creep increases when stress is high:

  • If σ ≤ 0.45 f’cmi → linear creep
  • If σ > 0.45 f’cmi → nonlinear creep

 Step 7: Design Creep Coefficient (φcc)                                        

Creep increases when stress is high:

ϕcc=k2×k3×k4×k5×k6×ϕcc,b

 Step 8: Creep Strain (εcc)                                                                      

Creep increases when stress is high:

εcc​=(ϕcc ​x σ)/Ec

Where:

  • σ = sustained stress
  • Ec = modulus of elasticity

This gives the actual deformation due to creep​

 Step 9: Final Creep (After 30 Years)

The final creep coefficient is obtained from Table 3.1.8.3.

Important limitation:

Stress must not exceed 0.45 f’cmi

Engineers should report:

  • Short-term creep (Step 8)
  • Long-term creep (30 years)

AS 3600 Creep Calculation – Interactive Example

Enter your values below to calculate the design creep coefficient, creep strain, final creep coefficient after 30 years, and final creep strain.

Results

Enter values and click Calculate.
Notes:
• Step 8 uses: εcc = φcc σo / Ec
• Step 9 uses the final creep coefficient after 30 years from Table 3.1.8.3.
• Step 9 is valid only for concrete first loaded at 28 days and stress not exceeding 0.45 fcmi.
• For values between tabulated values, interpolation is used.
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