A new design method for the openings of shell structures under the dual control of principal stress lines and stress contours

Abstract

Current design software lacks high precision and effective control in handling complex shell opening designs. This study develops a new workflow for generating shell openings based on the exceptional modeling advantages of Grasshopper, a visual programming language integrated with the Rhino software. The process contains two critical subroutines developed in Python for data processing and transformation. One is a selection tool based on the K-nearest neighbors classification algorithm for processing principal stress line data. The classification result is the guideline for shell meshing, which substantially improves the structural rationality of mesh shells generated based on dynamic equilibrium methods and particle spring systems. Another tool developed in this study based on the computer vision library OpenCV provides the functionality to read and process stress image data. In addition, this subroutine allows multi-level control of shell opening dimensions according to stress contours. In contrast with the conventional method, the new method efficiently brings shell form under the dual control of principal stress lines and stress contours for the first time. The obtained shell-opening results indicate increased freedom in layout, shape, and smoothness. The method is applied to a free-form shell, and three typical practical examples are presented to demonstrate its structural efficiency and visual effect.