This possibility occurs naturally wherever there are “thick walls”—alcoves, window seats, or any other small spaces at the outside edge of rooms, which can have lower ceilings than the main room and can therefore have their roofs shaped as continuations of the ceiling vault inside. This requires that thick walls be outside the structure of the main room, so that their roofs and walls come close to forming a catenary with the main vault.
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| Alcoves within the catenary. |
. . . next to the mosaic of subcultures (8), perhaps the most important structural feature of a city is the pattern of those centers where the city life is most intense. These centers can help to form the mosaic of subcultures by their variety; and they can also help to form city country fingers (3), if each of the centers is at a natural meeting point of several fingers. This pattern was first written by Luis Racionero, under the name “Downtowns of 300,000.”
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There are few people who do not enjoy the magic of a great city. But urban sprawl takes it away from everyone except the few who are lucky enough, or rich enough, to live close to the largest centers.
This is bound to happen in any urban region with a single high density core. Land near the core is expensive; few people can live near enough to it to give them genuine access to the city’s life; most people live far out from the core. To all intents and purposes, they are in the suburbs and have no more than occasional access to the city’s life. This problem can only be solved by decentralizing the core to form a multitude of smaller cores, each devoted to some special way of life, so that, even though decentralized, each one is still intense and still a center for the region as a whole.
The mechanism which creates a single isolated core is simple. Urban services tend to agglomerate. Restaurants, theaters, shops, carnivals, cafes, hotels, night clubs, entertainment, special services, tend to cluster. They do so because each one wants to locate in that position where the most people are. As soon as one nucleus has formed in a city, each of the interesting services—especially those which are most interesting and therefore require the largest catch basin—locate themselves in this one nucleus. The one nucleus keeps growing. The downtown becomes enormous. It becomes rich, various, fascinating. But gradually, as the metropolitan area grows, the average distance from an individual house
CONSTRUCTION
It is of course rare to be able to have the alcove or thick walls approach a true catenary section—we hardly ever want them that deep or that low. But even when the thick walls and alcoves are inside the line of the catenary, they are still helping to counter outward thrusts. And their buttressing effect can be improved still more by making their roofs heavy. The extra weight will tend to redirect the forces coming from the main vault slightly more toward the ground.
The drawing below' show's the way this pattern works, and the kind of effect it has on a building.
The effect of thickening the outer walls, shown m flan nnd section.
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21 I THICKENING THE OUTER WALLS
Therefore:
Mark all those places in the plan where seats and closets are to be. These places are given individually by alcoves (179), WINDOW PLACES (l8o), THICK WALLS (197), SUNNY COUNTER (199), WAIST-HIGH SHELF (20l), BUILT-IN SEATS (202), and so on. Lay out a wide swath on the plan to correspond to these positions. Make it two or three feet deep; recognize that it will be outside the main space of the room; your seats, niches, shelves, will feel attached to the main space of rooms but not inside them. Then, when you lay out columns and minor columns, place the columns in such a way that they surround and define these thick volumes of wall, as if they were rooms or alcoves.
For shelves and counters less than 2 feet deep, there is no need to go to these lengths. The thickening can be built simply by deepening columns and placing shelves between them.
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1 to 3 feet of thickness
A
outside the room
In order to make an alcove or thick wall work as a buttress, build its roof as near as possible to a continuation of the curve of the floor vault immediately inside. Load the roof of the buttress with extra mass to help change the direction of the forces—roof vaults (220). Recognize that these thick walls must be outside
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the main space of the room, below the main vault of the room— floor-ceiling vaults (219), so that they help to buttress the horizontal forces generated by the main vault of the ceiling. When you lay out columns and minor columns, put a column at the corner of every thick wall, so that the wall space, like other social spaces, becomes a recognizable part of the building structure-COLUMNS AT THE CORNERS (2 I 2) . . . .
2 12 COLUMNS AT THE
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. . . assume that you have worked out the roof plan, and laid out ceiling vaults for every room on every floor—roof layout (209), floor and ceiling layout (210). These vaults are not only the basis of the structure, but also define the social spaces underneath them. Now it is time to put columns at the corners of the vaults. This will both complete them as clearly defined social spaces—structure follows social spaces (205)—and also be the first constructive step in the erection of the building —gradual stiffening (208).
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We have already established the idea that the structural components of a building should be congruent with its social spaces.
In structure follows social spaces (205) we have established that the columns need to be at corners of social spaces for psychological reasons. In efficient structure (206) we have established that there needs to be a thickening of material at the corners of a space for purely structural reasons.
Now we give yet a third still different derivation of the same pattern—not based on psychological arguments or structural arguments, but on the process by which a person can communicate a complex design to the builder, and ensure that it can be built in an organic manner.
We begin with the problem of measurement and working drawings. For the last few decades it has been common practice to specify a building plan by means of working drawings. These measured drawings are then taken to the site; the builder transfers the measurements to the site, and every detail of the drawings is built in the flesh, on site.
This process criffiles buildings. It is not possible to make such a drawing without a T-square. The necessities of the drawing itself change the plan, make it more rigid, turn it into the kind of plan which can be drawn and can be measured.
But the kind of plans which you can make by using the pattern
2 12 COLUMNS AT THE CORNERS
language are much freer than that—and not so easy to draw and measure. Whether you conceive these plans out on the site—and mark them on the site with sticks and stones and chalk marks— or draw them roughly on the back of envelopes or scraps of tracing paper—in all events, the richness which you want to build into the plan can only be preserved if the builder is able to generate a living building, with all its slightly uneven lines and imperfect angles.