Generative Reciprocity: A Computational Approach for Performance-Based and Fabrication-Aware Design of Reciprocal Systems

Abstract

Using the capabilities of computation and digital fabrication this thesis provides a basis for a novel process of design to fabrication for reciprocal systems. In the traditional sense, reciprocal structures combine the advantages of timber as a renewable source of construction material and low-energy production with the modular fabrication, fabrication efficiency, structural capacities, and elegance of reciprocal interconnection of members. The unique benefits of reciprocal systems come from their discrete geometry, which simplifies the connection detailing and provides freedom for local and global variations in the system. However, this reduction in construction complexity and flexibility of local variation is replaced with geometrical complexity due to numerous compatibility constraints coupled with the structural behavior of the system. This research therefore identifies the key design parameters and design constraints of reciprocal systems. The results demonstrate the complex coupling of geometry, structural performance and fabrication in these systems, hence an essential need for application of an integrative design process. Through the application of computation, simulation, and digital fabrication this research proposes an integrative computational design process which can effectively address the coupling of design, analysis and fabrication of reciprocal systems and accommodate design exploration and optimization. First, a novel computational method for geometric modelling and form-finding is presented to resolve the compatibility constraints and generate the essential geometric and topological data for analysis and fabrication. Second, a flexible and scalable analysis method is implemented to study the interplay of the design parameters and the structural behavior of reciprocal systems. A comprehensive parametric study reveals a complex relationship between the geometric parameters and the structural performance and demonstrates the essential need for a real-time performance feedback for optimal design of free-form reciprocal systems. Third, a generalizable and efficient fabrication process is proposed for reciprocal systems with 3-D module geometry using 5-axis CNC machinery. Towards this goal, four different connection types are proposed, and different fabrication parameters are studied through digital and physical prototyping, destructive structural testing, detailed finite element simulation, and fabrication of a scaled structure. The results are summarized as a guideline for selection of the main fabrication parameters including joint detailing and fabrication tolerances. The computational design process is then developed by rethinking and replacing the conventional direct incremental development by a modular integrative computational process using multi-directional dataflow between different design phases. Finally, the proposed framework is used for a full-scale design to fabrication case study to validate the applicability of the proposed design process.