Technical design of the ETFE cushion envelope for the Parc des Expositions station (Grand Paris Express)

Abstract This project addresses the design and development of the main envelope of the Parc des Expositions (PEX) station, part of line 17 North of the Grand Paris Express. The main roof is composed of 308 ETFE pneumatic cushions, adapted to a unique vaulted geometry, defined by a metal supporting structure of arches spaced every 9 meters and connected by tie rods, generating a triangular mesh on which the cushions are installed. The station has a total height of approximately 21 meters and a length of 181 meters. The envelope embraces and covers the platforms, leaving the track area free. This lightweight envelope meets functional criteria by providing natural lighting, reducing structural loads, and offering a passive ventilation strategy thanks to its open configuration and the incorporation of perimeter metal meshes Each cushion consists of two or three ETFE sheets arranged in different configurations depending on their location: transparent or screen‐printed sheets, with the aim of controlling light transmission and solar factor, and meeting the aesthetic criteria of the architectural project. The total projected surface area is 2,744m 2 , with an actual installed surface area of approximately 4,000m 2 . The cushion system is fixed using lacquered aluminum profiles with EPDM sealing gaskets, which allow condensation water to drain. The profiles are anchored to the metal structure at specific points using welded bushings. The low‐pressure inflation system consists of two inflation units that distribute dry air through a network of ducts, ensuring constant internal pressure in each cushion. The system includes redundant fans and automatic pressure control mechanisms, guaranteeing structural safety in the face of variable weather conditions. In addition, the project incorporates two additional single‐layer ETFE covers to provide protection from inclement weather and visual continuity with the formal language of the station: a 73‐meter‐long and 8‐meter‐wide pedestrian walkway (568 m 2 ) and a bicycle pergola (80 m 2 ). Both roofs are made of a single transparent sheet reinforced with stainless steel cables. This solution, although less complex, maintains the principles of watertightness, drainage, and material efficiency. The intervention is a large‐scale reference for the use of ETFE inflatable cushion systems in public infrastructure, combining material and technological innovation with complex geometric design.