残损古建筑木结构叉柱造式斗栱节点抗震性能退化规律研究

Study on seismic behavior degradation of damaged “Dougong” joint built with fork column of Chinese ancient timber structure

为研究残损叉柱造式斗栱节点的抗震性能及其退化规律,以独乐寺观音阁平座层叉柱造式斗栱为研究对象,参照宋《营造法式》三等材的营造方法,制作4个叉柱造式斗栱节点,并采用人工模型方法,模拟构件表面腐朽、虫蛀及裂缝等三类残损斗栱节点。通过低周反复荷载试验,研究残损斗栱节点的破坏形态、滞回性能、抵抗弯矩承载力、转动刚度、耗能及其退化规律。试验研究表明:残损叉柱造式斗栱节点的破坏形态与完好斗栱节点相似,残损节点模型的破坏更显著、更严重;残损斗栱节点的弯矩-转角滞回曲线呈弓形,滞回环捏缩效应较小,层间滑移现象减弱;不同残损斗栱节点的抵抗弯矩承载力和转动刚度都有一定程度的降低;残损节点的耗能能力都有所提高;残损斗栱节点仍具有较好的变形能力和延性。初步建立了节点的残损度与其抗震性能退化之间的关系。研究成果对我国现存叉柱造式古建筑木结构的残损评估和保护具有重要参考价值。

To study the seismic behavior and performance degradation laws of damaged 'Dougong' joints, the'Dougong'joint of Guanyin Pavilion of Dule Temple was investigated. Based on the third-class material fabrication method of Song dynasty,four 'Dougong' joint models were fabricated with three types of damage produced by artificial corrosion,worm and crack, respectively. Based on the low-cycle reversed loading experiments for the failure characteristics,hysteretic behaviors,bearing capacity,degeneration of stiffness and energy dissipation,the seismic behaviors and degradation laws of the damaged 'Dougong' joints were analyzed. The results show that the failure patterns of damaged models are similar to those of intact model,but their destructions are more conspicuous and serious.The shapes of hysteretic curves of damaged models appear to be arched with small 'gathering effect' for the hysteretic curves,and the sliding phenomenon between components attenuates. The bending bearing capacity and rotational stiffness of the damaged joint models may decrease to some extent,while the energy dissipation capacity of the damaged joints can be improved and their deformation capacity and ductility can be retained. Eventually,the relationship between the damage degree and the degradation of seismic performance was established. The research results provide valuable references for damage assessment and preservation of existing ancient timber structures with 'Dougong' joint built with fork column.