# Research Progress on Curved Plates in China: Applications in Architecture
## 2 Image Expression of Curved Plates  
### Classification of Architectural Images  
In the 21 st century, with the development of new materials and technologies, architecture has gradually broken through the shackles of traditional acadism, and more design concepts and functional requirements have been represented [35]. Rationality and sensibility interweave in this process, and curved surfaces in buildings gradually show excellent expressive roles and practicability in modern architecture. The previous paper [1] provided theoretical classification based on the geometric and mathematical expressions of surfaces, but in this paper, we take actual Chinese curved surface building engineering cases as the research object and sort and compile them into a brand new classification system based on two dimensions, which are the design concept source and the role of curved plates as building elements in architecture (Figure 1, horizontal and vertical axes), as shown in 3 \(\times\) 4 cases in Figure 1. The idea of the specific classification is as follows. The appearance of curved surface buildings constitutes a \"shape\" that is accepted as a \"symbol\", which means that the architectural image is not only a shape but also an internal concept that has a certain spirit or common physical representation [36]. Therefore, the design concept sources of curved surface buildings can be mainly divided into local culture, natural imagery, humanity imagery, and construction purposes (Figure 1, horizontal axis classification). For local culture, the most direct reference for architecture is the people living around the building. By conforming to local social customs and behavioral habits, buildings can obtain the most basic historical identity and arouse resonance [37]. For natural and humanity imagery, both are conceptual recurrences of certain phenomena. The former focuses on imitating creatures and merging into nature, with soft curved surfaces and affinity [3], while the latter focuses on the positive and enterprising spirit and conveys expectations of life [38]. For construction purposes, these imagery types show the actual functions of buildings and strengthen the expression of functions of buildings themselves according to the intuitive expression of the external image, which coincides with the connotation of functionalism [39]. Therefore, curved surface buildings are divided in detail on the horizontal axis, but it should be pointed out that a specific building can have the ability to express multiple image relationships, but for the purpose of guiding design, this paper introduces a construction case that emphatically elucidates only the core image expression characteristics. Elements usually need to perform a certain function to realize the value of their arrangement, mainly in load-bearing and space separation [40]. Therefore, the classification of curved surface buildings according to the vertical axis is based on the building element roles played by the curved plates, which are mainly divided into load-bearing elements, envelope enclosures, and internal partitions (Figure 1, vertical axis classification). Specifically, as load-bearing elements, curved plates primarily bear the main load of the building and are the major force-bearing structure of the building. As an envelope enclosure, curved surfaces separate internal and external spaces and directly contribute to the appearance of the building. As internal partitions, curved surfaces have the effect of effectively and reasonably zoning building functions. Similar to the aforementioned horizontal axis classification, in actual curved surface buildings, a certain element often has multiple roles. To systematically summarize, only the main function played by a curved surface will be discussed. In addition, since the vertical axis is clearly and obviously divided, it can also express curved plates' contributions to building the architectural image.