Homes and gardens


Double arch  

The most fascinating chapter in history of architecture could be to find how humans managed to keep the roof up there. The idea of shelter must have started then.

It is believed that the earliest method of forming space could be by watching two branches kept inclined to each other supporting each other. So multiple such tree branches inclined together could form a secured space between them, creating a cone-shaped hut. Next four branches kept vertical with horizontal members on top could have created a flat roofed structure, but this would still be a small space considering the kind of branches one could get – not always straight, often bending in the centre, roof collapsing from the edge and such other mishaps happening.

All this would have changed with brick making, among the earliest technologies discovered by humans, shaping it with sun drying. Soon wall making complete with varied openings like doors, windows and perforations would have followed. One of the challenge was to support the wall part above the openings. That’s when, possibly, arches were discovered.

Arches transfer the wall load by compression, i.e. loads move from one member to another by pushing them vertically or diagonally, and not by tension where they move horizontally too like in a beam. How humans learnt about strength of curves could be an exciting research topic, for there were very few naturally curved objects to learn from. It’s possible, a playful curving of a twig could have led to trying out a wall opening with curved profile, creating the first arches in history.

In comparison to horizontal opening topped with flat lintel, the arched top offers multitude of benefits. Its profile changes with every variation in width and height, with a new look every time. There can be dozens of arch types, while flat lintel is flat for ever. Aesthetic theories associated with arches far outweigh those with horizontal ones. The indoor spaces and outdoor styles created by arches are unparalleled both in history and contemporary designs. Of course, along with advantages, also come challenges. If built upon a support system, its strength is unknown until the supports are removed. To construct the arch without such support takes some skill. A basic knowledge of geometry applied to construction is necessary to plan them out, depending upon the span, rise, springing point and key stone on top. Joint between arch edge and wall needs to be well thought out. Based on width of opening and load from above, arches may be in one or multiple courses. They also pose problems in fixing frames and shutters, including for windows or doors.

Despite challenges faced, arches continued to rule the world of architecture. When masonry construction declined, being replaced by frame systems, arches were in reduced demand. Now we are realising that framed buildings, especially those in RCC, have higher embodied energy, hence less sustainable. It’s time to revisit arches.

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Printable version | Nov 20, 2021 11:31:30 AM |

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