Form-finding method for free-form shell structures with zero bending moment

Abstract:

To design free-form structures with reasonable mechanical behaviors and rich geometrical shapes, the principles of traditional form-finding methods by physical experiments were referred, and a numerical form-finding method for free-form structures was proposed based on the combination of the Dynamic Relaxation method and the Local Linearization method. As the zero bending moment type free-form structure has the same form with the flexible membrane structure which has the same loading distributions and boundary conditions, the form-finding of free-form shell structures can be realized by membrane structures. In the proposed method, equilibrium forms under different driving forces, such as the gravity, pneumatic pressure, pretension force, were generated by Dynamic Relaxation method, and the form-control problem aiming to meet the requirements of architectural design was explored by adjusting the initial parameters of the model using the Local Linearization method. The poposed form-finding method was applied to the inverse-hanging type shells, the pneumatic type shells and the tension type shells separately. For the inverse-hanging type shells, a model made by Isler was simulated, and the results were compared with the data by 3D scanning to verify the accuracy of the proposed method. For the pneumatic type shells, the multi-region controlling strategy was used to realize the form-finding of complicated shapes. For the tension type shells, the behaviors of a shell genertated by the form-finding method were analized to illustrate the zero bending moment feature. It can be concluded that the proposed method is more effective and applicable, which is helpful to realize the harmonious design of architecture and structure.