基于预应力-耗能耦合机制的自复位木框架结构抗震机理与时变性能研究

With environmentally friendly characteristic and high level of prefabrication, timber frame becomes a preferred structural solution in terms of building industrialization. However, when subjected to major earthquakes, timber structures normally have excessive residual deformation caused by plastic damage in the connections. In most cases, it is either impossible or too expensive to repair the damage after the earthquake. Post-tensioned timber frame structures with self-centering feature provide an effective way to achieve seismic resilience, however there are a number of unresolved issues related to low lateral stiffness, poor peak dynamic response, and prestress loss during long-term service. To potentially address these issues, wooden braces are incorporated to increase the lateral stiffness, and energy dissipation devices are used to connect the braces to the main frame to provide energy dissipation as well as to mitigate the possible incompatible deformation between the braces and the timber frame. Pseudo static tests and nonlinear numerical modelling will be conducted to clarify the seismic behavior of the proposed self-centering timber frame structures. The interaction between the prestress effect and the energy dissipation mechanism within the structure will be revealed, and the self-centering mechanism of the structure will be thoroughly investigated. Moreover, long term monitoring for the prestress loss in the steel strand will be conducted to investigate the time-dependent load resisting characteristic of such structures. The influence of wood creep effect on the prestress loss will be revealed, and a formula for the evaluation of the prestress loss during the service life of the structure will be derived. Furthermore, the seismic reliability and failure probabilities of such structures will be evaluated based on incremental dynamic analysis. This project will make significant scientific contributions for understanding the seismic behavior and time-dependent characteristic of self-centering post-tensioned timber frame structures. It will also contribute to the development and utilization of novel seismic resistant timber structural system in China.

木框架结构绿色环保，符合建筑工业化发展方向，但强震后结构永久损伤明显，残余变形大，极难修复。通过施加预应力构建自复位体系是提升木框架结构抗震性能的有效途径。然而，自复位木框架抗侧刚度不足、峰值响应较大，且长期服役下预应力损失规律复杂。鉴于此，本项目在自复位木框架结构中引入与之变形协调的木支撑，辅以耗能元件吸收地震能量，通过试验和多尺度数值模拟研究结构抗震机理,阐明结构中预应力效应与耗能效应的协同工作机制，揭示结构动力响应规律和自复位机理。进行长期监测试验，基于理论分析解耦木材不同受荷模式下的蠕变对结构中预应力损失的影响，建立预应力损失预测模型及公式，揭示由于预应力损失导致的结构抗力时变规律。最后基于增量动力分析和可靠度理论，评估结构地震可靠度。本项目对揭示自复位木框架结构抗震机理和时变性能有重要科学意义，对构建新型可恢复功能木结构体系有重要工程应用价值。

虽然国内外针对自复位木框架结构的研究已取得初步成果，但仍需进一步科学审视预应力木框架结构的实现条件与性能需求，提出抗侧能力和耗能能力俱佳的结构方案。本项目首先从短期及长期性能角度对预应力木梁柱节点进行了系统研究，揭示了节点受力机理及其在温湿度变化环境下的预应力损失规律。随后将研究对象从构件层面扩展至结构层面，开展了预应力木框架结构的推覆分析，动力时程分析及可靠度评估。基于钢木混合理念，提出了解决预应力木梁柱节点核心问题的钢木混合节点，并通过理论分析、数值模拟及试验研究，探索了所提出新型节点的滞回特征及可恢复能力。考察了ADAS支撑及TOB支撑对预应力钢木混合框架力学性能的影响规律，建立了设两类耗能支撑预应力钢木混合框架的有限元模型，从拟静力及动力层面进行了两类框架的特性对比。随后开展了接近足尺的设耗能支撑预应力木及钢木混合框架往复加载试验，考察了支撑类型及钢木连接形式对框架力学特性的影响，解析了设耗能支撑预应力框架中耗能机制和自复位机制间的协同工作机理，为该类框架的设计提供了科学依据。