The Tour Phare is a highly innovative tower destined for construction in La Défense. Marty Doscher, Founder and Director of SYNTHESIS Technology Integration and formerly Technology Director at design studio Morphosis, has carefully crafted this arresting building whose cavernous atrium bears its structural bones for the world to see. The asymmetric silhouette of tower swells slightly near its base to incorporate a Grand Hall, tapering as it rises into a mass of wind turbines on the roof. A high performance double skin permits a flood of natural light but reduces solar heat while creating a memorable aesthetic presence in a busy urban environment.
Located on a small site crowded with others’ imaginative architectural concepts, the Tour Phare met numerous design challenges head on. Doscher explains: “The tower emerges from its irregular site, defined by a neighbouring motorway and a rail link, and bisected by an existing pedestrian walkway. It is located between the 1989 Grande Arche de la Défense and the 1958 CNIT building, the former exhibition hall of the National Inter-University Consortium for Telecommunications, with an architecturally significant glass façade, designed by Jean Prouvé.”
In reaction to the complex intrusions that impinged upon the Tour Phare’s footprint, a hybrid structural solution was formed. Resting on a tripod base, the tower comprises one splayed structural leg, two habitable legs (the Trapezium to the west, and the East Building) and a pavilion volume to transform the existing public plaza. At the building’s base rests a 24m wide by 28m tall void to be utilised as an urban gateway, however this unusual design solution was not without its troubles.
Project Architect, David Rindlaub furthers: “Early on, the building core was concrete and the rest of the structure was steel. In this configuration the concrete foot was integral to the structural integrity of the tower. Ultimately the tower structure changed to almost all concrete except for the steel diagrid structure of the grand hall. Because of the added stiffness provided by the additional concrete structure, the concrete foot ultimately became non-critical to the structural integrity of the main tower.
“The concrete foot is necessary however to reduce horizontal movement (sway) in the tower to allowable levels for the comfort of the building users. This change importantly accelerated the anticipated construction schedule because the main concrete tower can be built ahead of the installation of the steel grand hall diagrid.”
When faced with multifaceted design challenges, architects and engineers regularly turn to design technology to aid the creative process. Morphosis began working with 3D modelling software in the mid 90s and now uses BIM for the technical design of every project. When questioned on the positive ramifications of the software, Doscher explained: “Initially, the impetus was the management of complex design geometries, but the benefits are now recognised as two-fold.
“One, computational techniques afford the exploration of more options for geometries and patterns. Two, computational techniques enable the feedback from builders to become encoded into the design tools (that which governs the economy of making becomes captured in the design logic), so that as options are explored, there is a built-in measure of constructability.” In terms of this particular scheme, Doscher elaborated: “The design technology certainly reduced the size of the design team required to handle the immense quantity of information required to fully understand the design and execution of the project.”