木质梁的变湿蠕变及其与湿胀干缩的关系

Creep of Wood Beams and Its Relationship with Hygroscopic Expansion in Varying Humidity

为探知木质梁变湿蠕变的基本规律、其与恒湿蠕变的区别以及与湿胀干缩的关系,以杨木实木和LVL为原料,测试蠕变挠度和湿胀干缩量。结果表明:2.5个变湿周期内,实木和LVL的变湿蠕变总挠度,分别是同期内相对湿度为80%时恒湿蠕变总挠度的1.80和1.46倍;2个周期内的厚度湿胀干缩累积量,分别占变湿蠕变总挠度的-0.63%和1.27%。湿胀干缩不改变木质梁吸着蠕变的基本规律,但影响其吸湿蠕变和解吸蠕变的挠度,尤其对杨木LVL变湿蠕变总挠度的影响显著。

The bending deflection and hygroscopic thickness expansion of solid wood and laminated veneer lumber （LVL） beams under load were monitored in various humidity conditions to approach the basic law of the creep in varying humidity and its relationship with the changing dimension and the difference from the creep in uniform humidityResults showed that the total bending creep deflections （TBCD） after 2 cycles in RH 42%→80%→42% followed by an adsorption up to 80% were 180 and 146 times as those in the same period in the uniform RH 80% for solid and LVL samples, respectivelyThe accumulated thickness expansions after the 2 humidity cycles were -063% of the TBCD for the solid wood beams and 127% for the LVL beamsThe thickness expansion could not alter the basic law of mechanosorptive creep of wood beams,but affected the bending creep deflection from either adsorption or desorption, especially the TBCD of the LVL.