Abstract
The connections of a spatial truss structure play a critical role in the safe and efficient transfer of axial forces between members. For discrete connections, they can also improve construction efficiency by acting as registration devices that lock members in precise orientations. As more geometrically complex spatial trusses are enabled by computational workflows and the demand for material-efficient spanning systems, there is a need to understand the effects of global form on the demands at the connections. For large-scale structures with irregular geometry, customizing individual nodes to meet exact member orientations and force demands may be infeasible; conversely, standardizing all connections results in oversized nodes and a compromise in registration potential. We propose a method for quantifying the complexity of spatial truss designs by the variation in nodal force demands. By representing nodal forces as a geometric object, we leverage the spherical harmonic shape descriptor, developed for applications in computational geometry, to characterize each node by a rotation and translation-invariant fixed-length vector. We define a complexity score for spatial truss design by the variance in the positions of the feature vectors in higher-dimensional space, providing an additional performance metric during early stage design exploration. We then develop a pathway towards reducing complexity by clustering nodes with respect to their feature vectors to reduce the number of unique connectors for design while minimizing the effects of mass standardization.
Highlights
The complexity of a structural design is often the restricting factor to its realization
We provide a detailed overview of the conversion of an arbitrary spatial truss node and its force demands to a rotation-invariant feature vector using the spherical harmonic shape descriptor developed by [20]
We present an application of the spherical harmonic shape descriptor in the domain of nodal force demands in a spatial truss structure
Summary
For many similar structures built around the world, two missed opportunities are often evident: first, members are typically uniformly sized, resulting in unnecessary material consumption and the increase in structural mass. The design and detailing of nodal connections are uniform, despite an large variation in force transfer requirements. If a single standardized connection is used, it must be oversized for most of the structure, and providing registration for elements would be difficult for non-regular truss geometries In this case, complexity is inherent in the variation of the force demands at each node, and represents the lost potential of customization. The conversion of forces into a single geometric object resolves challenges in comparing the similarity of nodes with different numbers of element connectivity, and the use of the spherical harmonic shape descriptor provides invariance to the orientation of the node, allowing for recognition of similar nodal demands that are rotated or translated throughout a spatial truss. The feature vectors of all nodes provide the basis of a nodal distance matrix, which is used for a complexity metric when evaluating multiple designs, and for clustering analysis to strategically reduce the number of unique connections required for design and fabrication
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
