Buildings 2023, 13, 233. https://doi.org/10.3390/buildings13010233 www.mdpi.com/journal/buildings Article Experimental and Numerical Investigation of an Innovative 3DPC Thin-Shell Structure Wenfeng Du 1 , Liming Zhu 1, *, Hao Zhang 2 , Zhiyong Zhou 1 , Kewei Wang 1 and Nasim Uddin 3, * 1 College of Civil Engineering & Architecture, Henan University, Kaifeng 475004, China 2 School of Civil Engineering, Fuzhou University, Fuzhou 350108, China 3 Department of Civil, Construction and Environmental Engineering, University of Alabama at Birmingham, Birmingham, AL 35294, USA * Correspondence: 10160010@henu.edu.cn (L.Z.); nuddin@uab.edu (N.U.) Abstract: The development and application of new Fiber Reinforced Polymer (FRP) material and 3D printing construction technology provide a basis for making up for the shortcomings of tradi- tional thin-shell structures and building new thin-shell structures with better performance. In this paper, a new 3D Printing Composite (3DPC) thin-shell structure is proposed, which is prepared using a FRP plate as a permanent base mold and combining it with 3D printing cement technology. Both the typical experiment and finite element numerical simulation analysis of the 3DPC thin-shell structure are carried out. The results show that the maximum load capacity of the 3DPC thin-shell structure is increased by 53.3% as compared with the corresponding traditional concrete thin-shell structure. The presence of the FRP sheet effectively delays the generation of initial cracks and en- hances the ductility of components. Keywords: composite thin-shell structure; 3D printing; FRP sheet 1. Introduction A thin-shell structure is a kind of curved surface spatial structure with excellent bear- ing capacity, which has the advantages of a free and beautiful appearance, high stiffness and good integrity. Depending on the rationality of its geometric shape, the axial force is evenly distributed to the shell surface, thus making full use of the compressive perfor- mance of the material, so that the structure can cover a long-span space under a few cen- timeters of thickness [1]. It originated in ancient Rome and was mainly used in religious buildings, such as the Hagia Sophia Cathedral of Istanbul in 998 A.D, St. Peter’s Basilica of Rome in 1626, and the Taj Mahal of India in 1629 [2–4]. After the 20th century, with the rapid development of mechanical theories and the widespread application of reinforced concrete materials, new types of thin-shell structures were constantly emerging and widely used in various kinds of buildings, such as the Opera House in Sydney, the Na- tional Exhibition Center of Industry and Technologies in Paris, the Beijing Railway Sta- tion, the Xochimilco Shell in Mexico City, etc., many of which have become landmarks of a city. By the late 1970s, with the emergence of new spatial structural systems, the practical application of thin-shell structure had been greatly reduced [5]. It is mainly because more than half of the labour and material resources are wasted in the construction process, dur- ing which shell forming needs the erection and removal of temporary formworks and supports. According to the statistical results of engineering examples, almost 60% of the expense of a thin-shell structure is used for construction cost [6]. Another crucial issue is that thin-shell structure is usually sensitive to initial imperfections. The initial defects ex- isting in the long-span thin-shell structure reduce the ultimate bearing capacity greatly in the bearing process, which easily leads to buckling failure [7–8]. Citation: Du, W.; Zhu, L.; Zhang, H.; Zhou, Z.; Wang, K.; Uddin, N. Experimental and Numerical Investigation of an Innovative 3DPC Thin-Shell Structure. Buildings 2023, 13, 233. https://doi.org/10.3390/ buildings13010233 Academic Editors: Paulo Cachim, João Gomes Ferreira and Konstantina Vasilakopoulou Received: 30 November 2022 Revised: 6 January 2023 Accepted: 11 January 2023 Published: 13 January 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/license s/by/4.0/).