Creep Loading
Creep Loading - Related Videos
01:22
Creep in Concrete
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2024
Creep refers to the time-dependent increase in strain under a sustained load, excluding other time-dependent deformations associated with shrinkage, swelling, and thermal expansion in concrete. The primary mechanism behind creep involves the loss of physically adsorbed water from the calcium silicate hydrate within the hydrated cement paste. This process is further exacerbated by concrete's non-linear stress-strain relationship, microcrack development in the interfacial transition zone, and...
01:28
Factors Affecting Creep
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2024
In normal-weight aggregate concrete, the hardened cement paste is the primary contributor to creep, whereas the aggregates, being stiffer than the cement paste, are more resilient to stress-induced deformation. The stiffness of the aggregates is defined by their modulus of elasticity, and the more voluminous they are in the concrete, the less it will creep. Further, the water/cement ratio is critical, as a lower ratio increases concrete strength, thus reducing creep. The strength of the...
01:25
Effects of Creep
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2024
Creep in concrete, the gradual deformation under prolonged stress, significantly impacts the integrity of structures. For reinforced concrete beams, it can be a vital design consideration, as it increases deflection, sometimes necessitating additional design measures. In columns, especially slender ones under eccentric loads, creep can cause buckling, compromising their stability. However, creep can be beneficial in indeterminate structures by mitigating stresses that arise from shrinkage,...
09:51
Measuring Plant Cell Wall Extension (Creep) Induced by Acidic pH and by Alpha-Expansin
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Cited by 43 •
2009
We demonstrate the use of a constant-force extensometer to measure long-term extension (creep) of plant cell wall specimens induced by acidic buffers and expansin protein.
01:19
Impact Loading
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2024
Impact loading occurs when a moving object collides with a stationary structure, such as a rod with a uniform cross-sectional area fixed at one end. Under these conditions, the rod absorbs the kinetic energy from the striking object, leading to deformation and subsequent stress development. As the rod returns to its original position and reaches maximum stress, the absorbed energy, initially manifested as kinetic energy, transforms entirely into strain energy. In cases of elastic deformation,...
FAQs
The defining engineering challenge is that short-term strength alone cannot establish long-term safety. A component may remain below its short-term strength while its deformation continues under a sustained or slowly varying load. Creep-loading assessment therefore treats time as a governing variable, alongside applied stress, temperature, and environmental conditions, rather than evaluating load capacity at one instant.
A strain-time curve separates the response into three stages. Primary deformation begins with a decreasing rate, secondary deformation proceeds at a comparatively stable rate, and tertiary deformation accelerates. This progression is important because the final stage signals movement toward failure, while the secondary portion helps describe ongoing service behavior. Engineers use the curve to connect observed strain with expected service life.
Several microscopic processes can produce time-dependent deformation. Dislocation creep reflects the movement of crystal defects, whereas diffusion provides another route for material transport. In polymers, polymer chains can gradually move; in other materials, atoms or crystal defects are relevant. Identifying the dominant process helps relate the observed macroscopic strain to the material’s internal response during prolonged loading.
Keeping stress, temperature, and environmental conditions controlled is essential when interpreting creep data. Changing any of these variables can alter the deformation history, making strain-time curves difficult to compare directly. The loading history also matters: the response may be generated by a constant stress or by a load that varies slowly. These controls improve predictions of deformation, relaxation, and failure.
A practical characterization workflow applies a sustained or slowly varying load while recording deformation as a function of time. The resulting strain-time curve is examined for primary, secondary, and tertiary behavior under specified stress, temperature, and environmental conditions. Those observations support estimates of service life and help evaluate whether a design may experience unacceptable deformation, stress relaxation, or eventual failure.
Within engineering, creep loading matters wherever components carry long-term loads, especially in turbines, boilers, pressure vessels, and pipelines. It also applies to polymer components that remain loaded over time. Creep analysis lets designers account for progressive deformation rather than relying only on short-term strength, improving assessment of service life and long-duration performance in these systems.