高湿状态下单板层积材的横纹承压性能

Side compression of laminated veneer lumber in a high-humidity environment

重组加工是提高低强度木材结构性能的重要手段,以杨木重组加工的单板层积材为研究对象,从受力方式、承压方向及增强方法等方面研究了高湿状态下单板层积材的全表面、局部表面及尽端局部表面横纹承压性能。结果表明:湿环境对杨木单板层积材横纹承压性能影响较大,湿环境下其全表面横纹承压性能为干环境下的33%;杨木单板层积材横纹承压性能主要与其承压位置与承压方向有关,局部横纹承压时受到承压面周围木材纤维的支持作用显著,承压面平行于单板层时其局部承压强度最高,在干燥环境下,分别是尽端局部及全表面横纹承压强度的1.2倍和1.4倍。单板层积材结构是导致不同承压方向横纹承压性能差异的主要原因,承压面垂直于单板层时,单板层积材易过早发生分层或屈曲破坏。湿环境下单板层积材含水率较高材质较软,自攻螺钉支持作用明显,有助于改善其承压性能。杨木单板层积材横纹承压强度对环境湿度较为敏感,在工程应用时应保持环境干燥并使承压面平行于单板层。

Reorganization processing is an important means to improve the structural performance of low-strength wood.This study focused on laminated veneer lumber(LVL)produced through the reorganization processing of poplar wood.Specifically,the transverse compressive properties of the full surface,local surface,and end-point local surface of LVL under high-humidity conditions were investigated from the aspects of stress mode,pressure-bearing direction,and reinforcement method.The results indicated that moisture treatment had a substantial influence on the transverse compressive performance of poplar-based LVL,with the full surface compression under wet conditions being 33%of that under dry conditions.Under similar environmental conditions,the transverse compression of LVL was primarily associated with its compression location and compression direction.During local surface compression,the pressure-bearing face received significant support from the surrounding wood fibers.Notably,the local surface compressive strength was the highest when the pressure-bearing face was parallel to the veneer layers.Under dry conditions,the compressive strength of the local surface was 1.2 times that of the end-point local surface and 1.4 times that of the full surface.The compression differed notably with varying compression directions.When the pressure-bearing face was perpendicular to the veneer layer,the LVL was susceptible to early delamination or buckling failure.Under high-humidity conditions,the higher moisture content softened the LVL,but the strong support provided by self-tapping screws helped to reinforce its compression.In conclusion,the transverse compressive strength of poplar-based LVL exhibited sensitivity to environmental humidity.Therefore,in engineering applications,it is advisable to maintain a dry environment and ensure that the pressure-bearing face is parallel to the LVL.