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Today we're going to learn about how creep is measured in concrete. First, can anyone tell me what tools we might need for this process?
Do we need a creep frame and some gauges?
Exactly! A creep frame with a dead load helps us apply constant stress to the concrete sample. We also use dial gauges or LVDTs to record strain. Any other thoughts on the companion specimens?
Are the companion specimens loaded or unloaded?
Great question, they are un-loaded. This helps isolate the effects of shrinkage from total deformation. Let's remember this setup as CD - Creep Deformation, Companion Specimen; it highlights our measuring approach!
Why do we need the Creep Coefficient? Can someone explain what it represents?
Isn’t it the ratio of creep strain to elastic strain?
That's correct! It’s written as φ = Creep Strain / Elastic Strain at Loading. This coefficient is crucial for quantifying how much deformation is due to creep relative to the immediate elastic response.
What are some typical values for normal and high-strength concrete?
For normal concrete, it ranges from φ = 1.5 to 2.5, while high-strength concrete is from φ = 0.8 to 1.5. Remember this as 'Normal Needs More' versus 'High Needs Less'!
Involves specialized tools like creep frames, gauges, and companion specimens to determine deformation due to sustained load.
A significant ratio that measures creep strain in relation to elastic strain, helping engineers assess the long-term stability of concrete.
Creep takes time, on strain it will climb, measured with gauges, let’s check it on time.
Imagine a builder who constantly checks the building’s structure over time. Every time he adds weight, he measures the strain with his tools, making sure everything holds solid without cracking - that’s the essence of creeps.
For Measuring Creep, remember 'C.G.C.': Creep Gauge Companions!
C.R.E.E.P. - Creep Ratios Existently Effect Performance!
Term
What is a Creep Test?
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Term
What is the significance of the Creep Coefficient?
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Gradual increase in strain in concrete under constant stress over time.
A ratio used to measure the extent of creep deformation relative to elastic deformation.
A tool used to measure displacements in materials, often indicating strain in creep tests.
A device used to measure small displacements and strains.
Unloaded concrete samples used in testing to separate the effects of shrinkage from total deformation.
Creep is measured through specific test setups that isolate deformation caused by stress over time.
The measurement of creep involves a structured approach using specialized equipment to quantify strain over time under constant stress. The Creep Coefficient helps to quantify creep effects relative to elastic strain.
Creep in concrete is measured using a specialized setup that typically includes a creep frame subjected to a dead load. Essential equipment like dial gauges or linear variable differential transformers (LVDTs) record the resulting strain. Companion specimens, which are un-loaded, are often used to separate shrinkage effects from total deformation in experimental measurements.
The Creep Coefficient (φ) is a critical parameter defined as the ratio of creep strain to the elastic strain at loading:
Typical values for creep coefficients are approximately:
Understanding how to accurately measure creep is imperative in engineering applications, particularly to ensure the stability and longevity of concrete structures under sustained loads.