Novel form finding method for fabric formwork for concrete shells

This paper introduces a new form finding approach for the design of flexible formwork, consisting of pre-stressed structural membranes, for the construction of thin, anticlastic, concrete shells. The approach is based on the Force Density Method [1] and an adaptation of the non-linear extension of Thrust Network Analysis (TNA) [2]. First, the adaptation of the basic version of TNA to tension-only structures is discussed, and fundamental assumptions formulated. Key aspects herein are the use of reciprocal diagrams and the control of forces in indeterminate networks. Then, the strategy using an overall optimization process, for finding the closest possible tension-only, equilibrium surface to a given target surface under the appropriate loading (i.e. weight of the concrete), is presented. Finally, the strategy is applied to a chosen target surface and loads, and the equilibrium solutions for different starting points of the optimization process are discussed