The first picture, taken from several yards away, reveals a structure with steps, a roof, and walls, as well as two openings for entering and exiting. The whole structure is several yards in every dimension. The second picture, taken from a few feet away, shows that the walls are made of distinct concrete slabs attached to each other. Each slab is a few feet long and wide and several inches thick. The third picture, a closeup taken just inches from the surface of the concrete, reveals that the concrete is composed of sand and stones rigidly cemented together but loose enough that numerous air pockets are visible (if not in the low-resolution picture, at least upon close inspection of the structure itself). Most of the stones are less than an inch in every dimension.
The overall structure, with its rigidity and upright form, resembles a tree trunk. The thick trunk of an old hardwood tree supports the weight of the impressively tall verticals structure just as the concrete walls of the shelter hold up the roof. A tree trunk so powerfully resists compression that a car will crumple when driven into one, likely causing injuries for the passenger. The concrete would similarly resist deformity in a collision.
The uniform nature of the array of identical concrete slabs resembles the crystal structure of purified table salt (NaCl), which also has regularly spaced units tightly bonded together. A wall made of concrete slabs is strong and solid, just a salt crystal is also bonded strongly enough to resist melting until very high temperatures. Both concrete and salt, however, have their weaknesses. Salt dissolves easily in water at room temperature. Concrete displays an impressive resistance to compression, but cracks easily under tensile strain.
The concrete itself resembles glass. Glass is an amorphous solid that moves at room temperature, but not visibly. Similarly, concrete moves around when poured until it dries. Once it dries, however, concrete seems uniform from a large distance, although in truth it is a heterogenous mixture. Glass also contains several impurities that are not visible to the eyes.
The structure of the shelter at all three length scales has clues to its function. The concrete is a heterogenous mixture but it is frozen in place, which contributes to the rigidity of the concrete blocks. The uniformity of the blocks combines with the rigidity of concrete itself to lend to the shelter the strength which is so obvious to the viewer, and which is a key feature in a structure built for shelter.
I did not notice all of these fascinating aspects of the shelter until I did this assignment. As a resident of Van Pelt Manor house, I walk past the shelter every day on my way to classes and meals. I never stopped, however, to question how and why the shelter looks and functions as it does. Blogging about structure forced me to see this conspicuous object in a much more meaningful way.
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