【正文】 enary form based on a poetic geometric idea. This paper presents a constructiondriven design methodology that slightly adapts the numerical form found catenary shape with the objective of achieving planarity in all the triangulated, foursided and fivesided mesh faces. The challenge of facet planarity is gracefully solved by an analytical origami approach and presented. This approach is pared with finding the Maxwell reciprocal work diagram. The final faceted shape shows elegance and structural efficiency. DOI: (ASCE). 169。 2021 American Society of Civil Engineers. CE Database subject headings: Design。 Steel。 Glass。 Historic sites。 Roofs。 Netherlands. Author keywords: Shape。 Conceptual design。 Form finding。 Steel glass shell。 Historic courtyard。 Planarity faces。 Construction constraint。 Maxwell reciprocal work. Introduction In the wake of the Industrial Revolution, glass metal structures appeared as a result of two factors: society’s desire for green, quiet spaces in overpopulated cities, and the scientific emergence of new construction materials (glass and iron). In the early nieenth century, the first greenhouses with a glazed roof appeared as living spaces. Their tall construction and maintenance costs (because of the glass and the required heating system) made them style icons of the elite. Their curved shapes [(1) ridge and furrow ., Chatsworth, United Kingdom (built in 1834), and (2) vaulted, ., Kew, United Kingdom (built in 1844) (Kohlmaier and Von Sartory 1991)] allowed the sparse sunlight into the space and hit the citrus and lime trees (hence, the name orangery). Other varieties of tender plants, shrubs, and exotic plants were also housed in the orangery. The introduction of the palm tree, an impressive and prestigious plant with large religious significance, pushed the shape of the greenhouse further upwards. In the middle of the nieenth century, the development of greenhouse typologies was in full swing, and resulted in culture houses, conservatories, and winter gardens [., the Royal greenhouses, Laeken, Belgium (built in 1876) shown in Fig. 1 (Woods and Swartz 1988)]. The winter garden is of particular interest to this paper because it defines a social meeting place adjacent to a private mansion or public building. Mass production of affordable iron in the second half of the nieenth century further encouraged the design and construction of tall and large span exhibition halls made of cast and wrought iron and glass. Plenty of light entered the exhibition areas of buildings, such as the Crystal Palace, United Kingdom (built in 1851) (shown in Fig. 1). Its filigree iron structural skeleton was prefabricated, and it was subsequently dismantled and moved from Hyde Park to Sydenham in South London. Unfortunately, it was destroyed by fire in 1936. The second half of the 20th and the early 21st centuries experienced a new uprising of the design and construction of roofs over social gathering places, winter gardens without plants, covering courtyards of historically important public buildings [., the great courtyard of the British Museum, United Kingdom。 see Fig. 1。 the Deutschen Historischen Museum, and Museum fur Hamburgische Geschichte, Germany (both Schlaich Bergermann and Partners, built in 2021 and 2021, respectively)。 and the Smithsonian Institute, Washington, DC (Foster and Partners, and Buro Happold in 2021)]. The shapes of these glasscovered, singlelayered steel skeletal shells were driven by a bination of sculptural, geometric, physical, and constructional considerations (Williams 2021). The recent reemergence of these structures goes hand in hand with the evolution of digital design tools that enable the designer to develop and analyze more free and daring geometries. SingleLayeredSteelSkeletalShellsCoveredwithGlass Today’s designers (either from an architectural or engineering background) of these nonbotanical winter garden shells seem to be guided by one or more of the following four driving factors: Fig. 1. (a) Laeken winter garden (Belgium, built in 1875) still serves as a social meeting place. (Jackson 2021。 reprinted with permission from the photographer)。 (b) prefabricated Crystal Palace (United Kingdom, built in 1851) was dismantled soon after its intended use (reprinted from originally from Tallis’ History and Criticism of the Crystal Palace. 1852)。 (c) British Museum Courtyard (United Kingdom, built in 2021) steel roof adds value to the museum by expanding the useable circulation space (image by authors) imposed existing situation, sculptural architectural esthetics, geometric shape, and structural efficiency through form. Imposition on an Existing Situation: The Modern Winter Garden In the last two decades, existing historically relevant public buildings with a central open courtyard have been adapted to extend the useable floor area to an indoor/outdoor climate. These generally narrow buildings count on the courtyard for daylight. Steel and glass shells offer a unique solution to this design challenge. The historic context for these shells imposes a series of design constraints within which the designer has the freedom to develop the shell’s form. The boundary conditions often include height restrictions and limits upon the maximumextra load that can be imposed on the existing building, particularly in a horizontaldirection. The British Museum Court Roof is supported on sliding bearings so that no horizontal thrust is exerted on the historic masonry walls of the museum (Williams 2021). In the reviewing the design of recently realized steel shells, the driving design factor more often seems to be architectural scenographic esthetics rather than structural performance. Sculptural Architectural Esthetics With the available geometric digital modeling tools, more arch