带新型抗剪连接件木-混凝土组合梁力学性能及增强机理

Timber-Concrete Composite (TCC) beam is a novel type of composite structural forms, which has been applied in timber buildings and timber bridge engineering. However, the existing literature indicates that there still are some problems with TCC beams, such as low composite efficiency and relatively poor ductility. Given that, several types of novel shear connectors characterized by simple assembly, high load carrying capacity and shear stiffness are developed in this program aiming to create an eco-friendly, economical timber-concrete composite beam with high efficiency. This program mainly studies the basic mechanical behavior of the proposed shear connectors and the structural performance of the TCC beams with new shear connectors, involving (1) Push-out tests will be conducted on the proposed shear connectors to reveal the mechanical behavior and the deformation mechanism of the shear connectors. (2) Experimental and theoretical studies will be carried out on the TCC beams with novel shear connectors to investigate the flexural behavior of the composite beams. (3) Several TCC beams are strengthened using steel plates and fiber reinforced polymer materials and tested under four points bending. The load carrying capacity, bending stiffness and ductility of the strengthened TCC beams will be fully investigated to evaluate the strengthening efficiency on the TCC beams with novel shear connectors. (4) Scientifically reasonable design methods, structural measures and construction recommendations are proposed for the TCC beams with novel shear connectors. The implement of this program should be able to provide some references for the design and applications of timber-concrete composite structures.

木-混凝土组合梁是一种新颖的组合结构形式，已被应用于木结构建筑及桥梁领域。然而，已有研究表明，木-混凝土组合梁还存在一些问题，如组合效率不高、延性相对较差等。鉴于此，本项目提出了几种新型抗剪连接件，具有施工简便、承载力高、抗剪刚度大等优点，以期形成一种绿色、经济、高效的木-混凝土组合梁。本项目重点研究新型抗剪连接件的基本力学性能及采用新型抗剪连接件的木-混凝土组合梁的结构性能，主要包括：(1）新型抗剪连接件的推出试验，揭示其力学机理与变形机制；(2）通过带新型抗剪连接件木-混凝土组合梁受弯性能试验与理论分析，研究带新型抗剪连接件组合梁的受弯性能；(3）采用钢板及纤维增强材料对木-混凝土组合梁进行适当增强，并进行受弯性能试验，通过研究增强组合梁的承载力、刚度及延性等，对增强效果进行评价；(4）提出科学合理的设计方法、构造措施与施工建议。本项目的实施将为木-混凝土组合梁的设计和应用提供指导。

传统的纯木楼盖存在防水、隔声、楼板振动舒适度差等问题，在木楼板上部铺设混凝土层能在一定程度上有效解决上述问题。木-混凝土组合楼盖中的组合梁与钢-混凝土组合梁类似，其结构性能很大程度上取决于连接上部楼板与下部木梁的抗剪连接件的力学性能。本项目针对现有木-混凝土组合梁抗剪连接件总体上偏柔，组合梁效率不高、延性相对较差的问题，研发设计了三种新型装配式抗剪连接件用于木-混凝土组合梁，并在组合梁底部采用钢板及纤维增强材料进行增强。完成了68个钢-木组合节点的侧向加载性能试验，揭示了锚固件与木材之间的相互作用机理与变形模式，结果表明，螺钉或植筋连接钢-木组合节点具有良好的变形性能和可观的承载力，且中长螺钉或植筋在加载后期，力-位移曲线表现出了明显的“绳索效应”特征，另外，理论分析结果表明，欧洲规范5中关于钢-木连接接节点的承载力计算公式过于保守地估计了该类节点的真实承载力；进行了36个木-混凝土组合梁装配式抗剪连接件推出性能试验，并理论推导了不同破坏模式下，新型装配式抗剪连接件的抗剪承载力理论计算公式；开展了9根足尺木-混凝土组合梁受弯性能试验，其中8根为增强型梁，1根未增强梁作为对比，结果表明，采用CFRP和钢板增强，对木-混凝土组合梁的极限抗弯承载力有明显提高，提高幅度最高可达72%，但是对于组合梁的抗弯刚度的提升较为有限，最大提高为20%左右。增强机理主要表现为由于增强材料的存在，增强材料通过胶层及锚固螺钉与木梁底部协同工作，有效改善木梁底部受拉时的应力分布，进而使得增强型组合梁的木梁底部木纤维的极限拉应变得到提高。另外，底部增强材料在受弯过程中会产生张弦效应，对组合梁的整体抗弯性能和破坏模式均有一定改善。最终提出了关于木-混凝土组合梁的设计方法与施工建议。