ECC-RC组合T型深梁的剪切破坏机理及其抗剪承载力解析模型

针对广泛应用于高层建筑和桥梁结构的T型深梁抗裂/抗剪性能较差和大尺寸梁抗剪设计安全性不足等问题，本项目提出采用高延性混凝土-普通混凝土（ECC-RC）构建的新型组合T型深梁，研究ECC-RC梁间界面传力机制、组合梁剪切破坏机理，提出考虑梁尺寸效应的组合梁抗剪承载力解析模型。首先采用剪切摩擦试验，研究复合应力状态下ECC-RC界面的破坏机理和组合梁剪切斜裂缝处混凝土骨料咬合-纤维桥接机制；试验研究组合T型深梁的剪切性能，根据混凝土表面和纵筋、箍筋的应变分布，分析并验证钢筋和周围混凝土之间滑移与分离等非线性力学行为；最后，研究混凝土剪切摩擦、箍筋受拉和纵筋销栓等主要剪力传递机制，揭示梁尺寸对界面行为、混凝土-钢筋相互作用的影响机理，建立考虑组合深梁尺寸效应的抗剪承载力解析模型，形成优化设计方法。研究成果为该新型组合T型深梁的工程应用和设计提供理论基础和设计依据。

T-shaped deep beams are widely used in high-rise buildings and bridges. Durability, shear capacity and crack resistance of T-shaped engineered cementitious composites and reinforced concrete (ECC-RC) composite deep beams is significantly higher than conventional concrete beams. Furthermore, available design-oriented approaches cannot predict the behavior of large-size beams well. This research will investigate the interaction between ECC and RC, shear mechanism of the composite beam and analytical model for the shear strength of the composite beam. The shear friction tests will be conducted first to investigate the ECC-RC interface and the concrete-fiber friction along the shear cracking. Then the shear tests of T-shaped ECC-RC composite deep beam will be conducted. The strain distribution of the concrete, stirrups and longitudinal reinforcement will be measured to investigate and verify the non-linear mechanical behavior between steel and adjacent concrete. An analytical approach for the shear behavior of the proposed composite beams will be derived by quantifying each shear strength component including concrete, fiber, stirrups and longitudinal reinforcement. This approach allows for the size effect on the ECC-RC interface behavior, concrete shear friction and interaction between concrete and steel, which will be then simplified to an optimal design method. This study aims to provide theoretical basis and design guidelines for T-shaped ECC-RC composite deep beams.