基于非接触测量的陶粒混凝土预制底板平截面假定验证

Verification of Plane Section Hypothesis for Precast Ceramsite Concrete Base Plate Using Non-Contact Measurement

摘要: 为验证陶粒混凝土预制底板在受弯过程中是否满足平截面假定，本研究设计并制作了1块尺寸为3600 mm × 1100 mm × 80 mm的足尺试件，采用普通混凝土与陶粒混凝土组合结构，内部嵌入空心保温模具以提升保温隔热性能。通过堆载试验获取试件在各级荷载下的位移、混凝土应变、钢筋应变及裂缝发展数据，系统分析其受力全过程。试验结果表明：试件破坏时跨中挠度达112.2 mm，呈现典型延性破坏特征；荷载-位移曲线可分为弹性、裂缝发展和破坏三个阶段，反映了截面刚度退化与内力重分布过程；混凝土应变在开裂后非线性增长，中性轴显著上移；钢筋应变在开裂后快速增长，极限状态前接近屈服阈值。跨中截面应变分布和DIC应变演化图像显示，开裂前(P ≤ 0.2 F_u)截面应变呈线性分布，符合平截面假定；开裂后受拉区应变偏离线性，但受压区仍保持线性；极限阶段(P ≥ 0.9 F_u)受压区非线性加剧。综上，陶粒混凝土预制底板在整体受力过程中基本满足平截面假定，为同类复合结构的设计与分析提供了试验依据和理论支撑。

Abstract: To verify the validity of the plane section assumption for precast ceramsite concrete base plates under bending, a full-scale specimen with dimensions of 3600 mm × 1100 mm × 80 mm was designed and fabricated, featuring a composite structure of ordinary concrete and ceramsite concrete with embedded hollow thermal insulation molds. Pile loading tests were conducted to obtain displacement, concrete strain, reinforcement strain, and crack development data at various load levels, enabling systematic analysis of the entire mechanical response. The results indicate that the specimen exhibits typical ductile failure characteristics with a mid-span deflection of 112.2 mm at ultimate state. The load-deflection curve demonstrates three distinct stages: elastic, crack development, and failure, reflecting section stiffness degradation and internal force redistribution. Concrete strain increases nonlinearly after cracking with significant upward shifting of the neutral axis, while reinforcement strain increases rapidly and approaches the yield threshold prior to ultimate state. Strain distribution at the mid-span section and DIC strain evolution images reveal that strain follows a linear distribution before cracking (P ≤ 0.2 F_u), consistent with the plane section assumption. After cracking, tensile zone strain deviates from linearity whereas compressive zone strain remains linear; nonlinearity in the compression zone intensifies at the ultimate stage (P ≥ 0.9 F_u). In conclusion, the precast ceramsite concrete base plate essentially satisfies the plane section assumption throughout the loading process, providing experimental basis and theoretical support for the design and analysis of similar composite structures.