Learn: Approximate creep strain
A material under sustained stress can continue to deform with time. In a simple linear creep-coefficient model, creep strain is the additional time-dependent strain relative to an elastic reference strain.
What the formula is saying
First calculate elastic reference strain σ/E. Multiply it by creep coefficient φ to obtain additional creep strain. Total elastic-plus-creep strain in this simple convention would instead be (1 + φ)σ/E.
Read the symbols in plain language
- φ
- Creep coefficient
Creep coefficient. The creep coefficient multiplies the reference elastic strain without adding the elastic part again.
ratio / no unitA dimensionless ratio has no physical unit; 0.01 as a ratio is 1% when the percent option is selected.
- σc
- Sustained concrete stress
Sustained concrete stress. Matching stress units cancel in stress divided by the chosen reference elastic modulus.
PaOne pascal is one newton per square metre. 1 MPa = 10⁶ Pa.
- Ec
- Concrete modulus
Elastic stiffness: the stress change needed for a unit strain in the stated material model. It is not a strength limit.
PaOne pascal is one newton per square metre. 1 MPa = 10⁶ Pa.
- εcc
- Result to find
Approximate creep strain. The creep coefficient multiplies the reference elastic strain without adding the elastic part again.
ratio / no unit
Sort out the units first
σ and E must use the same stress unit, here Pa. φ and strain are dimensionless. A strain of 0.0005 is 500 microstrain or 0.05%, not 0.0005%.
Assumptions before calculating
Assume constant sustained stress in a linear creep range and a coefficient referenced to the same elastic modulus, age, time and environment. This lesson uses nonnegative compressive magnitudes rather than a tension-positive signed strain convention.
Let’s solve one together
Read the given values, follow each operation, then check what the result means.
Read the supplied values as one complete study case. Find εcc and explain the result in the stated output unit.
- φ · Creep coefficient
- 2
- σc · Sustained concrete stress
- 10000000 Pa
- Ec · Concrete modulus
- 30000000000 Pa
Calculate the reference elastic strain
Matching stress units cancel in stress divided by the chosen reference elastic modulus.
(10000000) ÷ (30000000000) ≈ 0.0003333333333Calculate only the additional creep strain
The creep coefficient multiplies the reference elastic strain without adding the elastic part again.
(2) × (0.0003333333333) ≈ 0.0006666666667
Does this worked answer make sense?
A zero creep coefficient gives zero additional creep strain, but not zero elastic strain. At fixed φ and E, twice the sustained stress gives twice the modeled creep strain.
A second worked example — different values
A second case uses different data. Predict which way the answer will change, then calculate it without reusing the first answer.
- φ · Creep coefficient
- 1.5
- σc · Sustained concrete stress
- 8000000 Pa
- Ec · Concrete modulus
- 32000000000 Pa
Calculate the reference elastic strain
Matching stress units cancel in stress divided by the chosen reference elastic modulus.
(8000000) ÷ (32000000000) = 0.00025Calculate only the additional creep strain
The creep coefficient multiplies the reference elastic strain without adding the elastic part again.
(1.5) × (0.00025) = 0.000375
Now try your own values
Change a value or its unit. The same method will show your calculation, step by step.
Results update only when you calculate. The lesson example above stays unchanged.
Your turn — check your understanding
Solve this separate case yourself. Use only the values below; the two worked examples use different data. Give the requested result in the selected unit.
- φ · Creep coefficient
- 2.2
- σc · Sustained concrete stress
- 12000000 Pa
- Ec · Concrete modulus
- 30000000000 Pa
Find: Learn: Approximate creep strain
A hint, not the answer
First calculate elastic reference strain σ/E. Multiply it by creep coefficient φ to obtain additional creep strain. Total elastic-plus-creep strain in this simple convention would instead be (1 + φ)σ/E.
σ and E must use the same stress unit, here Pa. φ and strain are dimensionless. A strain of 0.0005 is 500 microstrain or 0.05%, not 0.0005%.
Show the full practice solution
Compare the steps with your work; revealing a solution does not mark the lesson complete.
Calculate the reference elastic strain
Matching stress units cancel in stress divided by the chosen reference elastic modulus.
(12000000) ÷ (30000000000) = 0.0004Calculate only the additional creep strain
The creep coefficient multiplies the reference elastic strain without adding the elastic part again.
(2.2) × (0.0004) = 0.00088
Avoid the common trap
Do not add the instantaneous elastic strain when asked only for creep strain, or confuse φ with a strain percentage. Do not mix MPa stress with Pa modulus without conversion.
When this method applies — and when it does not
The formula does not determine φ from humidity, loading age, member size or duration. Stress changes require a time-dependent treatment; shrinkage and thermal strain are separate. Concrete code definitions of the reference modulus must be followed rather than mixed arbitrarily.
For study and understanding, not approval of a real structure, site operation or design. Apply the correct standard, National Annex and professional review to actual engineering work.
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Sources & further reading
References open in a new tab and explain the underlying principles. The teaching text and examples here are SimpleFlick’s own; the source organisations have not endorsed this calculator.
Reading focus: Approximate creep strain. First-generation EN 1992 teaching: material properties and the relevant bending, shear, serviceability, detailing or prestress relationship. Read the applicability conditions as well as the expression.
Lesson updated: · Both examples and the separate practice case are checked against an independent high-precision numerical implementation. This verifies arithmetic for the stated model, not engineering certification.