A paper bridge competition was held in 1990, at the University of Liverpool, as part of the European Architectural Winter School held there. The task was to design and construct a bridge, in 8 hours, from a limited palette of materials, to support 4 concrete building blocks (400 x 220 x 100mm), over a span of 2 meters.
The materials provided where; One sheet of 6mm thick corrugated cardboard (2440x 1220mm).
Two sheets of 1mm thick gray card ( 600x 400mm). One roll of 15mm wide masking tape, 20m long. One ball of 3mm, Hessian fibre string, 25m long.
The winning design was a folded plate structure designed by Clinton and Hamlyn Terry, together with a small group of architectural students from Scotland and Rumania.
Two key ideas drove the project.
Firstly by applying simple beam theory and then exploiting the non elastic property of paper in tension. No cuts as Doctor AA Griffith warns about stress concentrations.
The team began form finding by folding A4 paper sheets, this allowed a considerable number of forms and approaches to be considered. To start with the bridge span was increased by simply rotating the sheet on the diagonal. This in turn improved the shear stiffness, as the corrugated paper glue joints are now at 45 degrees to the dead load. Doctor L Euler makes himself present with the smallest of compressive loads, as paper is weak in compression, i.e. buckling. The bridge bearings therefore, a concrete block at each end. slot into the top cord (100mm wide), thereby avoiding as much as possible, buckling. The last thing to do was fold the rest of the sheet in such a way as to maximize the web depth to just under 440mm. The height of the bearing blocks . A reverse bend, similar to that used in Origami, was used to keep all fold radii constant, otherwise the 6mm corrugated card board would likely tear along the stress concentrations of a double bend.
The final design exceeded the competition requirements, supporting 4 concrete blocks together with a member of the design team, to the delight of all watching.