裂缝对胶合木螺栓节点和支撑框架抗侧力性能的影响机理研究

Glulam braced frame system accords with the development direction of prefabricated construction, and commonly applied bolted glulam joints have significant influence on the lateral performance of this structural system. However, under variable climatic conditions, cracks are easily induced in the joint area. This research object is glulam bolted joint and braced frame system, and intensive research is conducted on the influence of cracks. Cyclic loading test on full-scale joint specimens and refined numerical analysis will be conducted to reveal the influence law of crack characteristics (i.e. location, length and number of cracks) on the key mechanical indexes of joints, such as bearing capacity, stiffness, ductility, and energy dissipation capacity, and corresponding calculation formula of crack impact assessment will be proposed. Further, a theoretical model will be established to estimate the capacity of bolted glulam joints with cracks, and the influence mechanism of cracks on the capacity of joints will be clarified. Hysteretic mechanical model of bolted joints with cracks will be developed for different crack types. Based on lateral performance analysis of braced frame system, the influence of bolted joints with cracks on the lateral stiffness, capacity and ductility of the system will be clarified. This research has significant scientific and practical values for the safety guarantee of glulam structure. It will contribute to promoting the development and construction of modern and prefabricated timber structures.

胶合木支撑框架体系符合装配式建筑发展方向，体系中普遍采用的胶合木螺栓节点对结构抗侧力性能影响显著，然而节点区木材在外界气候条件的作用下极易产生裂缝。本项目以胶合木螺栓节点和支撑框架体系为研究对象，对裂缝影响机理展开深入研究。拟通过足尺节点试件的往复加载试验和精细化有限元分析，揭示裂缝位置、长度和条数等特征参数对节点承载力、刚度、延性和耗能等关键力学指标的影响规律，提出相应的影响评估公式；继而建立带裂缝胶合木螺栓节点的承载力理论解析模型，明确裂缝对节点承载性能的影响机理。针对不同裂缝形式，建立带裂缝胶合木螺栓节点的滞回模型；基于胶合木支撑框架的抗侧力性能分析，阐明带裂缝节点对结构抗侧刚度、承载力和延性等性能指标的影响机制。本项目对胶合木结构的安全保障、促进我国现代木结构的发展和构建装配式木结构建筑体系具有重要的科学意义和工程应用价值。

胶合木支撑框架体系符合装配式建筑发展方向，体系中普遍采用的胶合木螺栓节点对结构抗侧力性能影响显著，然而节点区木材在外界气候条件的作用下极易产生裂缝。本项目以带裂缝胶合木螺栓节点和单榀框架为研究对象，通过足尺节点试件的往复加载试验和精细化有限元分析揭示裂缝对节点滞回性能的影响机理，研究结果显示裂缝数目越多，对节点各力学参数的削弱作用越大；而裂缝长度的变化仅会对胶合木螺栓节点的弹性刚度有所影响，而不会改变其极限承载力。对于胶合木螺栓抗弯节点，裂缝的存在可使其弹性刚度和极限承载力分别下降25%和14%，而节点延性比和累积耗能的下降比率分别可达到30%和60%。对于胶合木螺栓支撑节点，相对于以销槽承压为主要破坏模式的节点，裂缝对以螺栓屈服为主的节点性能影响更甚，裂缝使其弹性刚度和峰值承载力分别削弱了45.9%和15.8%，节点累积耗能下降了24%左右。同时，胶合木单榀框架的抗侧力性能数值分析结果发现带裂缝胶合木螺栓柱脚节点亦会影响框架的抗侧刚度和最大承载力。基于以上研究结果，本项目拓展研究了采用摩擦耗能阻尼器加固带裂缝胶合木螺栓抗弯节点的方法，并基于试验和理论分析验证了该加固方法的有效性。研究结果表明摩擦耗能阻尼器显著提高了带裂缝抗弯节点的滞回性能，且有效改善了胶合木螺栓抗弯节点初始刚度低和滞回曲线捏缩等问题，带裂缝节点的弹性刚度和累积耗能分别提高了144%和613%。此外，基于准非线性断裂力学模型、Johansen屈服模型及节点力学平衡条件，提出了预测带裂缝胶合木螺栓节点和摩擦耗能阻尼器加固节点极限承载力的理论分析模型；并数值分析了摩擦耗能阻尼器加固带裂缝柱脚节点对胶合木框架抗侧力性能的改善效果，其抗侧刚度和抗侧承载力分别提高了 91%和 36%，累积耗能可提高 87%左右。本项目的研究成果对胶合木结构的安全保障、促进我国现代木结构的发展和构建装配式木结构建筑体系具有重要的科学意义和工程应用价值。