Experimental study on internal forces in continuous arch composite open‐caisson garage

Abstract This study proposes a novel continuous arched composite cross‐section caisson‐type underground garage structure to meet urban underground space development demands. Through scaled model tests, the mechanical performance and failure mechanisms under different rise‐span ratios (0, 0.1434, and 0.3) were systematically investigated. The experimental results demonstrate that when the rise‐span ratio is 0.1434, the structure achieves optimal mechanical performance, with cracking load reaching 197.8 kN/m 2 and ultimate load reaching 342.8 kN/m 2 —representing 2.5 and 1.7 times improvements, respectively, compared to other ratios. In this configuration, the structure primarily resists axial compression with significantly reduced bending moment effects, exhibiting stiffness increases of approximately 2.9 and 1.8 times compared to other ratios. Crack pattern analysis reveals uniform distribution under the optimal ratio condition, primarily resulting from buckling effects rather than conventional flexural cracking. The study confirms this structural form combines the mechanical advantages of arched structures with the spatial efficiency of rectangular layouts, providing an innovative solution for underground development in densely populated urban areas. The research findings offer valuable references for optimizing similar underground structures.