高温预处理对杨木正交胶合木剪力墙抗侧力性能的影响

Effects of Thermal Pretreatment on Lateral Performance of Poplar Cross-Laminated Timber Shear Walls

[目的]研究往复荷载作用时国产速生杨木正交胶合木(CLT)剪力墙的抗侧力性能,阐明木材高温预处理和加速老化对剪力墙抗侧力性能的影响,为高温改性技术和国产速生木材在建筑结构中的高效利用提供参考。[方法]以木结构建筑常用的进口欧洲云杉规格材为对照,以相同强度等级的国产速生杨木为研究对象,选用180℃为预处理温度对杨木进行高温改性,制备5面全尺寸正交胶合木剪力墙,开展往复荷载作用时加速老化前后正交胶合木剪力墙的抗侧力性能试验。[结果]与相同层板强度等级的欧洲云杉正交胶合木剪力墙相比,往复荷载作用时未处理杨木正交胶合木剪力墙的极限承载力、弹性抗侧刚度、耗能能力分别降低5.8%、12.9%、8.0%;木材经高温预处理、墙体经加速老化或二者联合处理后,杨木正交胶合木剪力墙的抗侧力性能指标不同程度降低;与未处理杨木正交胶合木墙体相比,加速老化处理后,墙体的极限承载力、弹性抗侧刚度、耗能能力分别降低9.4%、9.7%、11.2%;木材经高温预处理后,经加速老化,墙体的极限承载力、弹性抗侧刚度、耗能能力变化较小,分别降低2.9%、2.4%、5.0%。[结论]往复荷载作用时,国产速生杨木正交胶合木剪力墙的抗侧力性能略低于相同层板强度等级的欧洲云杉正交胶合木剪力墙,水平力作用时二者具有相似破坏模式,均为抗拔连接件节点处钉子被剪断;木材经高温预处理、墙体经加速老化或二者联合处理后,杨木正交胶合木剪力墙的破坏模式均为底部墙角抗拔连接件处木材被拉断或劈裂破坏;木材高温预处理能够有效降低加速老化对剪力墙抗侧力性能的影响,具有相对较好的抗老化能力;建立正交胶合木剪力墙极限承载力计算模型,理论值与试验值误差小于10%。

[Objective]The lateral performance of cross-laminated timber(CLT)shear wall made of domestic fast-growing poplar wood(Populus spp.)was investigated under cyclic load.The effects of wood thermal pretreatment and wall accelerated weathering on the lateral performance of CLT shear wall were determined.The results might serve as a valuable reference for thermal modification and effective use of low-value fast-growing wood in buildings.[Method]The CLT wall made of fast-growing poplar wood was taken as the research object,and its lateral performance was compared to that of commonly-used spruce(Picea abies)CLT wall in timber structures.According to previous studies,poplar wood was thermally treated at 180℃,and a total of five full-scaled CLT shear walls were prepared and tested in this study.The lateral performance tests of CLT shear walls with the absence and presence of accelerated weathering were performed under cyclic load.[Result]The peak load,elastic lateral stiffness,and energy dissipation of the untreated poplar CLT shear wall under cyclic load decreased by 5.8%,12.9%and 8.0%,respectively,as compared to those of spruce CLT shear wall with the same laminate strength class.The characteristics of lateral performance of poplar CLT shear walls reduced to varied degrees,after thermal pretreatment of wood,accelerated weathering treatment of walls,or a combination of the two treatments.Compared with the untreated poplar CLT walls,the ultimate bearing capacity,elastic lateral stiffness,and energy-consuming capacity of the CLT shear wall,after accelerated wall weathering treatment,reduced by 9.4%,9.7%,and 11.2%,respectively;and the wood was treated with high temperature.After accelerated weathering,the ultimate bearing capacity,elastic lateral stiffness,and energy consumption capacity of the CLT shear wall changed less,decreasing by 2.9%,2.4%,and 5.0%,respectively.[Conclusion]The lateral performance of the fast-growing poplar CLT shear wall under cyclic load was slightly lower than that of the spruce CLT shear wall with the same laminate strength class.The poplar CLT shear wall failed in a manner similar to the spruce wall.The damage to spruce and poplar CLT walls under lateral load conditions was mostly caused by screw breakage.The failure mode of poplar CLT shear wall made of thermally-treated poplar was wood fracture or split at the connection,which was identical to the failure mode of the accelerated weathering CLT wall and accelerated weathering wall manufactured using heated wood.Thermal pretreatment of wood can reduce the influence of accelerated weathering on the lateral performance of shear walls,resulting in comparatively strong resilience to wall degradation.The theoretical lateral peak load of CLT shear walls was established,and the error between the theoretical and test value was less than 10%.