交变荷载下木构件增强端部钉节点抗剪性能
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摘要
为克服木构件端部易开裂、力学性能差等不足,采用粉状碳纤维对木材端面进行增强处理,研究了木构件增强后端部钉节点在交变荷载下的受剪性能。结果表明:在单调荷载下,碳纤维增强后的水曲柳和落叶松木材端部钉节点抗剪力得到大幅改善,分别提高102.54%和78.23%;交变荷载能加速木构件端部钉节点损伤进程,交变荷载频率及荷载变化幅度是影响钉节点抗剪性能的主要因素;不同树种及不同端面钉节点剪切位移增量差异明显,剪切位移增量可用作评价交变荷载下钉节点抗剪性能优劣的参数;增强端面钉节点剪切破坏模式主要表现为钉孔边缘碳纤维涂层出现局部变形及钉剪切变形。增强后的水曲柳及落叶松木构件端面具有更优异的抗疲劳及蠕变性能,可应用于木结构工程。
In order to overcome the shortcomings of easy cracking and poor mechanical properties of wood member's end, the wood members' end was reinforced by using powdered carbon fibers. The screw joints shearing resistance capacity of wood members' reinforced end under alternating loads was studied. Results showed that under monotonic load, the screw joints shearing resistance capacity of Fraxinus mandshurica and Larix olgensis wood members' reinforcement end has been greatly improved, increased by 102.54% and 78.23% respectively. The alternating load could accelerate screw joints' damaging process. Alternating loading frequency and load amplitude were the main factors affecting the shearing resistance capacity of screw joints. The displacement increment which varied among different species and different ends was approved as a reliable evaluation parameter of screw joints shearing resistance capacity under alternating load. The shear failure mode of wood members' reinforced end was displayed by forms of local deformation of carbon fiber reinforcement layer aside screw and screw's shear deformation. Fraxinus mandshurica and Larix olgensis wood members' reinforcement end possessed more excellent anti fatigue and creep properties than unreinforced end, and could be applied to wood structure engineering.
In order to overcome the shortcomings of easy cracking and poor mechanical properties of wood member's end, the wood members' end was reinforced by using powdered carbon fibers. The screw joints shearing resistance capacity of wood members' reinforced end under alternating loads was studied. Results showed that under monotonic load, the screw joints shearing resistance capacity of Fraxinus mandshurica and Larix olgensis wood members' reinforcement end has been greatly improved, increased by 102.54% and 78.23% respectively. The alternating load could accelerate screw joints' damaging process. Alternating loading frequency and load amplitude were the main factors affecting the shearing resistance capacity of screw joints. The displacement increment which varied among different species and different ends was approved as a reliable evaluation parameter of screw joints shearing resistance capacity under alternating load. The shear failure mode of wood members' reinforced end was displayed by forms of local deformation of carbon fiber reinforcement layer aside screw and screw's shear deformation. Fraxinus mandshurica and Larix olgensis wood members' reinforcement end possessed more excellent anti fatigue and creep properties than unreinforced end, and could be applied to wood structure engineering.
引文
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[2]Yang X J,Gong M,Chui Y H.Short-term creep behavior of CFRP-reinforced wood composites subjected to cyclic loading at different climate conditions[J].Bioresources,2014,9(2):1845-1857.
[3]Kim Y J,Harries K A.Modeling of timber beams strengthened with various CFRP composites[J].Engineering Structures,2010,32(10):3 225-3 234.
[4]Jankowski L J,Jasienko J,Nowak T P.Experimental assessment of CFRP reinforced wooden beams by 4-point bending tests and photoelastic coating technique[J].Materials and Structures,2010,43(2):141-150.
[5]杨小军,杨茵,陈炼,等.聚丙烯腈基碳纤维增强木构件端面的工艺[J].福建农林大学学报(自然科学版),2016,45(5):586-592.
[6]Yang X J,Gong M,Chui Y H.End reinforcement of wood member using short-cut carbon fibers[J].European Journal of Wood and Wood Products,2015,73(2):159-165.
[7]Zhang J L,Yadama V,Quin F.Resistance of southern yellow pine to direct withdrawal of staples[J].Forest Products Journal,2002,52(9):75-81.
[8]Foschi R O,Bonac T.Load-slip characteristics for connections with common nails[J].Wood Science,1977,9(3):118-123.
[9]Erdil YZ,ZhangJL,EchelmanC A.Holdingstrengthof screws in plywood and oriented strandboard[J]. Forest Products Journal,2002, 52(6):55-62.
[10]MarlorR A,BulleitWM.Load-durationbehaviorofwood connections[J]. Journal of Structural Engineering, 2005, 131(9):1434-1443.
[11]杨小军,杨茵,陈炼,等.落叶松木构件碳纤维增强端部的握钉性能[J].森林与环境学报,2016,36(3):295-300.
[12]杨小军,孙友富.木构件螺钉结合持久性能研究[J].福建林学院学报,2012,32(1):93-96.
[13]祝恩淳,陈志勇,潘景龙.覆面板钉连接的承载性能试验研究[J].同济大学学报(自然科学版),2011,39(9):1280-1285.
[14]岳孔,陈秀才,刘伟庆,等.重复钉入对花旗松握钉力的影响[J].中南林业科技大学学报,2016,36(5):129-132.
[15]李玲,李大纲,徐平,等.疲劳/蠕变交互作用下竹木复合层合板断裂损伤研究[J].北京林业大学学报, 2006, 28(2):124-127.
[16]周吓星,李大纲,吴正元.环境因子对木塑地板疲劳/蠕变性能的影响[J].木材工业,2009,23(4):9-11.
[17]曹磊,张仲凤,曾丹.落叶松胶合木梁疲劳性能试验研究[J].建筑结构学报,2016,37(10):27-35.
[18]中华人民共和国建设部.木结构设计规范:GB50005-2003[S].北京:中国建筑工业出版社,2004.