Verification of Flexible Cable-net Formwork Method for GFRC Panel Manufacturing Using Structural and Physical Optimization

The cable-net formwork method has attracted attention as a low-cost and environmentally friendly way to realize free-form concrete shells. In this method, the doubly-curved surface of the membrane is controlled through wire end position and tension; Block Research Group has clarified the design process[1], which has been used to realize large-scale prototypes[2][3]. On the other hand, few studies have examined items necessary for application to actual architectural production, such as accuracy and formwork reusability. In this study, cable-net formwork is applied to the manufacture of curved GFRC panels in Japan, and a highly flexible formwork method is proposed that allows the same formwork to be reused even if the panel outline, curved surface shape or curvature changes. Furthermore, a design method is also proposed to minimize errors between the target shape and the manufactured panel by using a method to calculate the initial tension and support conditions by structural and physical optimization. Using the parameters determined by optimization, a total of 52 adjustable wire end positions is fixed. The tension of each wire is controlled by the number of revolutions of the turnbuckle, and different tensions are introduced for each wire as determined. The above process produced four sets of two line-symmetrical panels, a total of eight panels, whose geometry was measured. Furthermore, the 3d-scanned panels were arranged onto the structural frame model and their position was also measured. Using these measurement data, the applicability of this method to architectural production was verified from three perspectives: reproducibility of target shape, reproducibility in manufacturing, and deviations in construction.