I understand what 'strained' means in a dictionary sense, but believe this to have a precise meaning for architects and builders. Can any professionals in that area help, please?
- Deputy Grecian
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https://www.brighthubengineering.com/st ... 0discussed.
Engineering strain can be defined as the deformation of a material as the result of an applied force or load. This may be the result of static, constant load application and/or from dynamic, variable loading. Several theories or models are used to analyze these deformations. In the small strain model the material displacements are arbitrarily small and may be considered elastic, where the material recovers from the deformed state to its original dimensions. The large strain model considers the difference between the original material state and deformed state to be large and macroscopic, which may result in viscous flow, meaning the deformation is permanent. A combination of permanent and recoverable deformation, called visco-elastic strain, may also be considered. While many materials experience some form of visco-elastic deformation under load, for obvious reasons materials used in structural engineering are designed to experience only elastic, small strains. Permanently deforming a structure such as a bridge or building is usually considered to be an undesirable situation, as previously discussed.
The general mathematical equation for strain is:
Strain = dimensional change / original dimension, or ε = Δ R/Ro
Where R is a dimension such as length, width, angular displacement, etc., Ro is the original dimension, and Δ R is the difference between the deformed dimension and the original dimension.
Just as with stresses, strains are considered axial, or normal, if they occur in line with the applied load. These are termed tensile or compressive strains. If the deformation occurs parallel to the plane or area of applied stress, it is termed shear strain. A simplified example of this deformation is the motion of the top face of a square block of rubber with respect to its parallel, anchored bottom face. Applying a shear stress to the top face results in sideways displacement of the top of the block. Dividing that displacement by the original height of the block gives the shear strain. However, structural strain rarely so simple, as it usually involves complex deformations with both normal and shear components. But utilizing these straightforward models of stress and strain in materials has led to the computational design, modeling, and analysis tools so useful in the structural design process.
- GE (Great Erasmus)
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That's all very well if the stresses and strains are within the elastic limits of the material, so that, when the stress stops, the strain reverts to zero. If the stress is an explosion, it's unlikely that everything will pop neatly back into place when the explosion has finished, so some distortion or "strain" will persist. The stress lasts for a moment, but the strain lingers on. So, the buildings probably were indeed strained. Mr Flecker might have been choosing his words carefully.
Col A 1954-62
I had actually read the document to which you refer, but, being a simple-minded person, just could not understand it and was looking for a simple explanation. Plus, hopefully, some comments on what it might have meant for the C.H. buildings, which had been in the vicinity of the explosion of just under one ton of HE. For example, did it mean that they (or parts) were in imminent danger of falling down, or needed minor repairs, or were visibly deformed, or what? I know for certain that Maine B lost 247 windows, and the Dining Hall lost a number of stained glass windows(which were not only some distance away from the blast but also faced the other direction), so the blast was pretty dramatic. I should add that Mr Flecker was most certainly not a scientist and I suspect that he was given the term in a discussion with an architect or some other specialist and simply passed it on.