Design process of prestressed membrane formworks for thin-shell structures

This paper describes the digital design process of a fabric formwork applied to one of several adjacent concrete shell roofs for a private arts building to be constructed in 2017 in Brooklyn, NY, USA. This work is part of a larger feasibility study that compares this construction method to existing alternatives. Although the force distribution under load of the fresh concrete can be exactly computed for a fabric formwork, built examples show only modest spans and, where known, high construction tolerances. Among several causes, the main reason is thought to be the difficulty in reproducing the exact force distribution on site, which is more easily achieved in a discrete cable net than a continuous membrane formwork. In the latter case, the stress distribution is governed by the cutting patterns, making their design crucial to control of these tolerances. Towards this end, the design process laid out in this paper adapts the procedure for cable-net and fabric formworks to one for purely fabric formworks by computing stress distributions and flat cutting patterns.