Architects: Izquierdo Lehmann: Izquierdo Lehmann Arquitectos
- Year : 1997
Text description provided by the architects. The project is located in an area of Santiago that underwent urbanization as a garden neighborhood in the mid-20th century, and which, during the last decade, has suffered intense densification with buildings ranging from 7 to 20 floors high. Land values in this area has have become the highest in Santiago, reaching US$2800 per square meter. The project originated as a real estate operation whose profitability depended on selling the maximum buildable area of open office plans, repeated vertically, commercial spaces at ground level, and underground parking spaces. Common facilities were reduced to the minimum.
In order to contribute the least to the volumetric and formal disparity generated by the abrupt, badly regulated growth that characterizes the neighborhood where our building was to be inserted, we designed it as a simple and clear volume. Composed by a seventeen floor-high tower shaped as a regular parallelepiped, it touches the ground at the open corner of the plaza facing it, flanked by a lower and more opaque volume, 10 floors high, on its two opposite sides against the existing buildings in the interior of the block. This volume accommodated 9490 square meters of built surface, somewhat less than the theoretical allowance of the lot, but with an additional quality, that arises from having only two plan configurations, of 249 and 678 square meters each, whose orthogonal silhouette and dimensions allow for an optimal use of the office floors of double and triple corridor configurations, respectively.
The location of the vertical core within the interior circulation zone of the larger floor-plates, which coincides with the eastward circulation areas within the smaller floor-plates in the top volume, allows the upper section of the fire staircase to remain open. On the rear side of these scissor-shaped, crossed staircases is the elevator bank, that opens directly onto the interior of the office floors. This compact solution of the central core is suitable for the sale of entire floors and allows for a reduction of the incidence of common spaces on the ratio of sellable areas within the building.
The office levels are served from their perimeter by power and HVAC networks, and by terminals located within the central core, which houses the toilet facilities. In this way, suspended ceilings are avoided and greater internal headroom is provided. The post-stressed, long-span slabs have no reinforcing beams on the underside. Enhancing usage flexibility, they rest on their perimeter, on the walls of the central core, and on just four columns in the large floor-plates and a single one in the smaller plates. Windowsills facilitate the installation of office furnishings, while fulfilling fireproofing regulations. They house the horizontal stretches of ventilation and electricity ducts.
The facades of the tower show the simple overlaying of spaces, open to the maximum to natural light and distant views through continuous horizontal windows. Windowsills are inverted beams held by the least possible number of cilindrical columns. They are determined by the length of their span and the variable distribution of loads along the vertical development of the building. High-performance glazing contributes to an efficient thermal control of the building without resorting to shading elements –a topical response employed in westward facades. This focuses the interest of the architectural volume on the expression of the adopted structural solution, which is exposed as the outermost layer of the façade. We have preferred a corporeal architecture, one with shadows and thicknesses, over an architecture of shininess and surface virtualities.
The underground construction, destined for parking, is of a size comparable to that which rises above ground level. The combined surface area of these four and a half underground floor plates is 7007 m2. Aside from 252 parking spaces at 27 m2 per car, they contain water tanks, storage and service areas. This yield is achieved through four and a half offset plates, each 16 meters wide, each of which accommodates a double loaded circulation street, connected via ramps. The placement of the structural columns of the building was determined by the 2.5 meter module of the parking spaces.
The main problem to solve in the design was the offsetting of the office block from the underground parking areas. Both were composed and dimensioned according to their own specific laws. They had to overlap necessarily at the location of the circulation shaft. This encounter is resolved on the first two levels, which contain the main and secondary access, aside from retail spaces with street frontage. The total built surface occupied by these programs amounts to 75% of that permitted by the existing regulations.
The perforated, load-bearing walls of the wrapping volume have greater structural rigidity than the facades of the tower, which are composed of a series of beams and columns. This creates a structural asymmetry that is reflected in the displacement of the centers of mass and rigididty of the floor plates. In order to prevent oscillations and bending forces on the higher floors as a consequence of this, a variable grid of columns and diagonal girders was introduced. Compensating for the variable stiffness of an asymmetric volume, the design of the facades of the tower was realized through an interactive process of structural calculation meant to equalize the loads on cylindrical columns that have the same cross section and similar resistance, so that there would be no structural redundancies. Thus the facades show the diagram of dead and live loads reflecting the unstable condition of our seismic ground. The structure is built in reinforced concrete. It was left exposed on girders and columns while walls were clad with gray granite.
An office building does not require an internal connectivity that would profit from a unifying atrium; rather, it should care for the independence between the different floors, a condition that restrains the play of spatiality on these projects. Instead, this building type consists of a repetitive raising of the ground, as in a vertical subdivision. It is then the structural effort of this successive raising of floor plates, the vertical construction, which constitutes the architectural theme of this project.
In designing this work we sought to take the step, without shortcuts, “from the useful, through the truthful, to the beautiful”, following Goethe’s aphorism, so that, loyal to the real circumstances from which it arises –but not to stereotypical icons- it would contribute to forging our own identity.