New York – Living Cities – Architectural Processes, Complex Shape

THE AIM
Like other urban areas around the world, New York City will face dramatic population growth in the coming decades. Demographers predict that New York alone will add one million more residents by 2040. Finding housing will pose a crisis for hundreds of thousands of them, unless new residential towers are built to house this urban influx. We care about giving a satisfactory answer to the increase in population through Architectural, Structural and Energy solutions capable of ensuring high living standards without compromising the environment and guaranteeing hight efficiency. The building site is in fact characterized by an important yet chaotic living density, and lacks green areas of some importance. Seeing what we have, our main aim is to design a skyscraper which imitates nature, mirroring a tree’s birth, growth and life. If New York can no longer affords green spaces with extensions like Central Park, then why not to develop the concept of green city in a new direction, switch vertically its parks and gardens? Greenery can in our idea evolves back from its modern decorative role to its ancient, vital role as a founding element for the benefit of the building inhabitants and of those who happen to pass it by. In this perspective, architecture reveals itself in the basic (simple, essential) form of a parallelepiped, upon which nature can express its colors, strengths and tensions in dynamic, organic and ever-changing combinations.

THE CONCEPT

There is a striking similarity between the growth of a tree (green plants) and the building process: the excavation and the foundations are no different from the planting of a seed. The core of the skyscraper is the second step, potentially containing all its functions, connections and vital elements since the beginning, for the well being and the functioning of the whole building to be. At the top, a big crown sustains through steel ropes all the storeys below. The floors are realized in metallic carpentry, safely built at the core of the foundations, protected from the weather and thus containing the environmental impact on the adjoining areas (neighborhood). Once assembled and equipped with the basic plant network, they are raised to their final position (from the top floor to the bottom one), connected to the core and finished.

The imaginary of the suspension bridges of the Big Apple is thus absorbed into the skyscraper. The trunk and the branches are taking their shape. The core is so much less incident than the floors and the resultant modifiable spaces are open to adaptation to satisfy every functional need.

MODULARITY: The Construction
This structural system, with a definite delineation between the reinforced-concrete and structural-steel parts, lend itself to slip-form method of pouring the center core. The concrete core will be constructed with a continuous day and night operation using a mobile formwork. The second stage of the construction is the erection of the roof girders and the draping of the floor-supporting cables. After completion of this operation the erection of the typical floors progress at a rate of about one floor per day. To simplify and speed cable erection and to properly compensate for cable elongation due to load, the floor clamp locations are pre-marked on cables during the prestretching operation before cables were brought to the site. To overcome the elongation due to temperature changes, the design provides that the cables be enclosed in the climate-controlled interior of the building.

Once the structural-steel erection is completed the steel floor decks will be placed and studs weld to beams for composite action followed by the placing of the concrete topping. When the construction of the floors it’s completed the main beams will be rigidly connected with tubular profiles covering the hanging cables in order to ensure the correct positioning of the floors and to provide an additional resisting system in order to increase the structural robustness.

The external reticular frame has to be pre-tensioned with a proper force in order to involved the structural system when occurs a lateral action like the wind or the earthquake.

MODULARITY: The Floors The structure of the building we are proposing is a catalytic yet free element: it permits to aggregate different housing and service units varying in form and shape; these are in fact realized in prefabricated wood structureswith high energy efficiency (<10 kWh/m2) in customizable standard modules. These modules are based on a 1,5 meters grid complete with structural planking and paths distributions, ready to be put at use in both public and private green areas in the floors. The housing units can be pre-assembled together with the floors or easily disassembled afterwards; part of the central core is destined to a hoist system to transport the building elements for the housing units. The theme is not to purchase a ready-made apartment, but to get a portion of floor on which to build one’s own home. The quality of life grows thanks to the green spaces belonging to every housing unit able to make up for the lack of public parks in urban centres. Trees and vegetation, located in the peripheral crown of every storey and external to the structural element, live in the storeys alongside man, and architecture restores the natural equilibrium.

MODULARITY: The Skin

Progressively, with the same building logic used for the realization of the floors, the external shell takes shape: it behaves exactly as leaves on a tree, converting solar energy into vital energy for the building; thus the solar tower is born. The catalyst element is the external skin, modulated on a Voronoi diagram where the decomposition of the surface is determined by structural parameters, solar lighting exposition (orientation, possible obstacles etc.), internal and natural lighting needs and energy efficiency factors. The skin is not a rigid and closed system, but it expresses the vertical tension of the building in the construction phase and lets itself be modified by the context in which it lays: it is the stream of the city life which determines the tearing in the ground root (traffic, pedestrians, communications), the winds in height which cause the detachment near the covering crown, it is the trees between the floors that open windows to watch the sky. The skin is like a leaf, reading its context and elaborating it, absorbing energy and giving it back into a new form; architecture becomes the vector of this exchange.

THE STRUCTURE

In this building the vertical core is used as usual for the stairs, elevators and the technological systems and of course this is the main structural element subjected to the lateral forces as seismic and wind action. The idea if hanging the floors from the top of the centre core leads to the following advantages:

• application of increased vertical loads to the core improves the stability, and through the prestressing effect achieved the tension stresses in the core can be eliminated;

• the absence of columns improves the use of the underground parking levels, by providing column-free space;

• careful manipulation of the required floor area and number of floors led to the realization that the whole building could be carried on a center core without affecting its dimensions established for conventional buildings.