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Pneumatic wall with Zero footprint

This project shows how an effective solution was provided to a requirement for coherently matching the provisional enclosure element to the peculiar architecture of the building.

Muro neumático con huella Zero

For the celebration of the fiftieth anniversary of the establishment of the company Orona, a leading manufacturer of lifts and escalators in Europe, as well as for its annual shareholders’ meeting and the opening of the ORONA Ideo Innovation City complex in Hernani (Spain), the company’s management commissioned Xabier Barrutieta, the architect responsible for the new architectural complex, to find a solution making it possible to accommodate the 1,500 shareholders invited to the event.

The problem to be solved was that the space to be designed had to coexist with the architecture of the Orona Zero building, the company’s new headquarters, be coherent with it, and allow easy mobility for those attending towards the building to be opened. It also had to take account of the short-lived nature of the event, so the intervention had to leave no mark on the building and, once the events were over, dismantling had to be quick and easy. It also had to be possible to use the material again for future annual meetings. However, according to Área Cúbica, one of the companies participating in the engineering of the solution, “The most demanding challenge was to find a technical solution which, while meeting the above requirements, did not transmit to high levels of force to the pre-existing structure, as this had not be calculated for such a purpose.”

The solution finally adopted was a removable pneumatic wall, fixed from the outer edge of the false ceiling to the ground and running all around the perimeter of the covered square generated by the overhang of the new Orona Zero building.

Eventual solution

The solution finally adopted was a removable pneumatic wall, fixed from the outer edge of the false ceiling to the ground and running all around the perimeter of the covered square generated by the overhang of the new building.

The pneumatic wall technique consists of pressurizing the existing space between two parallel planes of membrane which must be joined by connecting elements. There are different possibilities and each of them will give the final object a different appearance. Basically, two of these possibilities could be considered: connection via a grid of interconnected points or using lines connected using another membrane that we call a rib or tympanum.

In this project the second solution was chosen: the two membranes were connected using vertical ribs, making the whole wall look as if it has vertical furrows, as can be seen in Figure 2.

Technical description

In these projects there are two zones with different solutions, always within the same double pneumatic membrane system:

  1. Front zone. This involves closing the main facade with an inclined pneumatic wall, following the same slope as the facade of the building.
  2. Rear zone. This incorporates a vertical enclosure element and a ceiling, smaller than on the main facade but of the same type of construction.

The project is interesting largely for two reasons. Firstly, the strength of these walls and ceilings had to be analyzed in relation to the outside actions they would have to withstand. Secondly, there was the design of the details for connecting this new pneumatic structure to the existing building, which would also have to allow fast periodic assembly and dismantling.

The central section of the main facade required careful study as it was the highest area (practically 11 m, inclined 75º to the horizontal). The wall has a rib every 150 cm and is pressurized with an internal pressure of 80 kg/m² (800 Pa) with respect to the exterior pressure. To analyze the behavior of this structure, WinTess software, created for the design and calculation of membranes under traction, has been used.

In the initial position, without any outside load, the wall takes on a flat surface on the outside, while inside it forms a convex curve inwards (on both sides there are undulations due to the pressure and the ribs).

The main action to which the wall will be subjected is the wind. It will either be upwind or downwind and the first of these provides the most unfavorable circumstances, on which the hypothesis is based. When the wind hits the wall it does so on the outer layer, which is subject to an internal pressure of 800 Pa. Whether the wind pressure is greater or lower than this value, the outer membrane will tend to be displaced towards the inside, so the intermediate volume will reduce and the internal pressure increase.

If we assume that the wind pressure is Pv = w · Ce · Cp (dynamic wind pressure multiplied by the earth coefficient and the pressure coefficient), in the balance the internal pressure of the wall must be equal to or greater than Pv, so the inner membrane will have a pressure equal to or greater than Pv. If this increase in internal pressure occurs, the reduction in volume will be very small, as we must not forget that the constant PV = k (Boyle-Mariotte) is a function of the real pressure, and pressures of 800 Pa are very small compared to the 100 kPa of atmospheric pressure.

Bearing in mind that the suction forces (if downwind) will be very small, the shape of the wall has been adjusted for upwind pressure. The internal sheet of the wall has taken on a curved shape, so it will move as little as possible when the internal pressure of the wall increases.

Fixing

For the practical purposes of assembly and dismantling, as well as in order to control deformation and the fixing points on the floor and the ceiling, a different solution has been designed for each case.

At the bottom, double fixings have been designed on both the outside and the inside so that both membranes are connected to the ground, while, at the top, only the internal membrane has been fixed, as it is the one that receives the greatest load due to wind action. In the case of suction, the outer membrane will be disconnected from the top front part and will develop the resistance required due to the cover of the internal chamber.

Although the movement is greater, at the top it has been possible to have a single row of fixings, in accordance with the technical requirement, instead of the two rows put in at the bottom.

Technical data / Ficha técnica
Name of the project // Nombre del proyecto: ORONA WALL

Client // Cliente: ORONA S.COOP

Architecture firm // Arquitectura: XABIER BARRUTIETA - LKS Ingenieria S.Coop.

Structural engineering firm // Ingeniería estructural: RAMON SASTRE - AREA CUBICA, SL - LKS INGENIERIA S.COOP

Contractor // Contratistas: ORONA S.COOP

Membrane engineering firm // Ingeniería de la membrana: RAMON SASTRE - AREA CUBICA, SL

Assembly and design of membrane // Montaje y diseño de la membrana: AREA CUBICA, SL

Textile manufacturer // Fabricante del tejido: FERRARI

Trade name of fabric // Nombre comercial del tejido: PRECONTRAINT 702 - 402

m2 textile used // m2 tejido utilizados: 5160

Source (who provides the data) // Fuente (quién proporciona los datos): AREA CUBICA, SL - ORONA S.COOP

Software: WinTess