Building crossings in wicker : flexible construction of a post-formed footbridge in active bending stiffened during service phase

The first traces of basketry date back to the Sumerian’s period (4000 years BC). From now on, these braiding techniques have been used to craft vernacular shelters, clothes, furniture and tools. However, they are uncommonly used in architecture and are generally limited to non-structural filling elements. To our knowledge, the Baya project developed in 2020-2021 at ENSA-Paris-la Villette and CentraleSupélec schools was one of the first examples of a braided wicker structural shell in architecture. Based on the braiding optimization algorithm developed during this previous project, our research intends to question one step beyond : crossings. This innovative research is demonstrated by the realization of a 12.8-meter-long footbridge for the Utopies Constructives festival in Richelieu’s Park. The footbridge, which echoes the reed boats of the Uros, a Peruvian tribe, will be braided flat before being moistened and shaped by buckling ; then it will be stiffened post-buckling by braiding the railings together. Building in a flexible way, then stiffening during the service phase is both the constructive process of elastic gridshells and the one used by basket weavers who braid the green wicker, which then stiffens once the object is formed.