Bifurcating Bridge 2010

Introduction

The Bifurcating Bridge project proposes a new footbridge that connects some of the older spaces of the Architectural Association with the recently acquired design studios on Morwell Street. This structure connects three different levels of the school via spanning across a small courtyard. The bridge is best described as a hybrid structure, both bridge and staircase. The name of the bridge is derived from its characteristic Y-shape in plan. The aim of this branching morphology is to facilitate circulation and visual interaction.
The Bifurcating Bridge is a student project that is part of the ongoing design research of the EmTech studio 2009/2010. It is being developed in collaboration with students from the Institute of Computational Design (ICD) in Stuttgart. The design reflects the EmTech course’s interest in digital design and manufacturing; the overall process represents typical methodologies of working that oscillate between digital design and rapid prototyping. In this manner the design progresses through the use of parametric tools and physical study models at different scales. The set-up of the workflow allows for a hierarchical design approach and in return simultaneously develops different areas of the proposal. Within this process is a constant collaboration with professional consultants Buro Happold Structural Engineers and Zurich-based company Design to Production.

Global Form and Design

The Bifurcating Bridge consists of three flights of stairs that depart from the three given anchor points and meet at a common central platform, resulting in its characteristic Y-shape. In addition to the formal and functional considerations (optimised circulation), this scheme has structural advantages. From a structural point of view, the design can be reduced to four curved beams that coincide with the perimeter of the bridge. The adopted logic is different from that of conventional beam-based bridge design: intrinsically, structure, handrails, and treads yield an integrated system.

Component-Based Design

A fundamental aspect of the design is the concept of repeated and connected units. The components design is a U-shaped element, replicated continuously as one typical stair riser, in addition to one distinctive component forming the central platform. The sidewalls, acting as handrails, connect to create structural continuity along the upper edge. The repetition of the component system not only gives the advantage of manageable on-site assembly, but also allows for component mass production, enhancing time efficiency and reducing the error factor.

Early on, wood was selected as the most suitable material to build the Bifurcating Bridge, due to labour expertise and workspace limitations, given that all project phases (schematic design to construction) were to be carried out by students utilising the Architectural Association Schools workshops and facilities. This prerequisite drove the design process and influenced the outcome of the final design. Different material solutions were investigated, such as laminated plywood and wood composite structures. Due to structural considerations and fabrication limitations, a wood core with plywood on either side became the final material selection.

Construction

Working models at a 1:5 scale and prototypes of the components at a 1:1 scale have confirmed the production process based on the logic mentioned above. Triangular shaped zipper units could easily be produced using regular band saws with a high degree of precision. Substituting multiple laminated layers of plywood reduces production time, provides quality control, and cuts cost.  Considering the nature of the project, the development of the material and manufacturing methods were crucial, as the chosen solution allows for more in-house work and traditional craftsmanship rather than CNC-milling, in addition to reducing costs on transportation, storage, and production logistics.

Both models are currently on display at this year’s AA Projects Review. The bridge is scheduled for construction in late summer 2010.