An Aesthetic Evaluation of Novel Forms in Free-Form Shell Structures The Perspective of Specialists

Abstract:

The structural system of a building, beyond providing mere stability, exerts a decisive influence on its performance, user experience, and aesthetic quality. With technological advances enabling the creation of novel structural forms—most notably free-form shell structures—aesthetic issues have grown more complex, and judgments about aesthetic quality demand clear, multi-dimensional frameworks. This study therefore set out to identify and systematize the criteria that specialist architects employ when evaluating the aesthetics of free-form shell structures and to develop a conceptual framework to guide both design and assessment.

To generate shared visual stimuli, a series of Catenary shell structural models were form-found using the Dynamic Relaxation method implemented via the Kangaroo plugin in the Grasshopper environment for Rhinoceros software. These stimuli were presented within semi-structured interviews to thirteen architectural experts; the discussions and participants’ responses were audio-recorded and transcribed verbatim. The resulting textual data were then subjected to repeated, in-depth readings and analyzed using thematic analysis framed by a hermeneutic–phenomenological approach. Coding proceeded in an open, reflexive manner, with descriptive and interpretive codes iteratively consolidated and organized into higher-order categories and conceptual themes.

The analysis shows that experts’ aesthetic judgments constitute a complex, multilayered process that interweaves objective and subjective, formal and conceptual criteria, and cannot be reduced to one or two singular indicators. Rather, the perceived beauty of free-form shell structures emerges from the interaction and synergy of four principal dimensions. First, formal aesthetics, emphasizing proportions, geometry, symmetry and balance, and formal variation — attributes of the shell’s shape and appearance that establish visual coherence and legibility. Second, perceptual aesthetics, encompassing human scale, interactivity, spatial quality, affective responses (including perceived safety), mental schemas toward form, innovation, and legibility — factors that shape the user’s sensory and cognitive experience. Third, structural-functional aesthetics, concerning integration with the ground, structural stability and behavior, and the detailing of connections; connection details in particular attracted sustained attention from experts as elements that simultaneously determine functional performance and aesthetic expression. Fourth, contextual aesthetics, which refer to the harmony of form with its setting and environment, responsiveness to climatic conditions, integration with nature, and resonance with cultural backgrounds and schemas. Together, these layers indicate that for architectural specialists’ beauty is inherently multidimensional, elevating shells beyond purely morphological objects to become meaningful, functional, and context-responsive buildings.

In addition to these dimensions, the study identified an “implicit intersubjective standard” among experts: although individual preferences and interpretations vary, a tacitly shared set of values and criteria consistently guides professional judgments. This implicit consensus facilitates the emergence of a common evaluative language and provides a foundation for developing systematic assessment tools.

Finally, the proposed conceptual framework can guide architects, structural engineers, and educators to ensure that, during the design process, formal and perceptual qualities, structural-functional requirements, and contextual considerations are attended to concurrently. Moreover, the findings furnish a basis for the development of quantitative analytic tools and machine-learning algorithms capable of linking qualitative aesthetic parameters to measurable formal and structural features. Such an integrative approach not only deepens understanding of aesthetic judgment in architectural shells but also supports the optimization of form with respect to sustainability, performance, aesthetics, and meaning.