Other modern buildings take a different approach. If strong winds, or any other force, put the building under stress, the centrally located core absorbs it, channeling it down and barely flexing, making the building almost impossible to topple. Cores are typically made of steel or concrete, and they help channel external forces. You can think of a core as a building’s spine. But some buildings are so large that they require something extra: a core. The frames of most structures employ nothing more than these four basic components. Running its length, you can see a triangular patterning – these are trusses at work. For a famous example, take a look at the Golden Gate Bridge. Trusses are often used in the construction of bridges. They’re more practical than beams, since the component parts are easily transportable and can be put together on-site, and their triangular shape is inherently stable. Trusses are triangular supportive frameworks composed of columns, beams and struts. If a space is too large for beams to span unassisted, then trusses can be employed to give extra stability. The sections of a frame that are neither horizontal nor vertical are referred to as braces, or struts. When stood upon, or when roofing material is laid across them, they channel the weight out to the columns upon which they rest. They are what’s typically used to form the skeletons of floors and ceilings. Especially impressive are the columns of the Parthenon, in Athens, and those of the Roman Forum, in Rome.īeams are long, solid horizontal supports, usually made of wood, steel or reinforced concrete. Ancient Greeks and Romans perfected the use of columns, turning these vertical sections of a structure’s frame into a form of art. Take pretty much any structure, and you’ll find that its frame is made of a network of beams, braces, columns and trusses.Ĭolumns are upright pillars, and they’re usually used to channel compression. And, really, modern buildings aren’t so different from LEGO constructions: each is composed of a variety of smaller components. And they’re no less important today.Ī great many engineers were first bitten by the building bug as children, and plenty of them experienced the wonders of construction while playing with their first LEGO set.
Unlike the mud huts, these structures used the frame system: the weight of the structure was channeled through the logs, which, by pushing against each other, were in tension.Ĭompression and tension, and the two systems we came up with to channel them, have been integral to construction since the first buildings were erected. They’d then seal the structure against the elements by draping animal pelts or woven plants over it. Once they gained access to suitable trees, they began building houses by lashing logs together. As far as we can tell, their first structures were single-story mud huts, which made use of the load-bearing system: the weight of the building was channeled down through its thick mud walls, putting them in compression.Īt some point, our ancestors also learned about tension.
Two towers sparknotes how to#
Our ancient ancestors certainly knew how to channel compression, even if only intuitively. So, early on, we devised systems designed to do just that. If we were unable to channel these forces, we’d be incapable of building anything. For example, if you were to pick up a bowling ball, your arm would be in tension. In contrast, when weight is hung from an object, force flows down and away from the object, putting it in tension. For instance, when you stand upright, your legs are in compression, supporting the force exerted by your body weight. When weight is placed on an object, force flows down from the weight, putting the object in compression. Every intact building is a testament to the deep understanding that engineers have of nature’s forces, and of the stress those forces exert on artificial structures.īroadly speaking, there are two types of force that put stress on structures: compression and tension. Unfortunately, it’s usually only when something like this happens – when a chief engineer makes a miscalculation and disaster ensues – that structural engineering enters the news.īut the triumphs of structural engineering abound. The disaster lasted less than 20 seconds, and 75 workers lost their lives. Construction had been underway for four years, but on that fateful afternoon, a large section of the bridge collapsed. Lawrence River, a crew of 86 workers were building the Quebec Bridge. On August 27, 1907, high above Canada’s St.
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