预应力积成材力学性能试验研究与有限元分析

Experimental research and finite element analysis on mechanical properties of pre-stressed laminated strand lumber

通过木材单板叠加试验和预应力积成材参数化分析试验及相应的有限元分析验证,研究了单板及预应力积成材在跨中集中荷载作用下受力模式、变形形态、承载力以及破坏模式的变化规律,并探讨了预应力的大小,螺杆的布置方式、直径、纵向间距及上下边距对构件承载力的影响规律。结果表明:随着板材积成数量的增加,预应力积成材的破坏模式由弯扭变形导致的强度破坏逐渐转变为由面内弯曲导致的强度破坏,承载力大幅度提升;预应力过大、螺杆直径过大和间距过小导致木材承压破坏或产生贯通裂缝,而预应力过小、螺杆直径过小和螺杆间距过大均不足以限制板材的侧向扭转变形,导致材料强度无法充分发挥;木节等木材初始缺陷严重削弱板材的承载力。最后针对本文研究的板材规格,提出了能够应用于工程实际的预应力施加建议。

Based on the superimposition experiment of wood veneers and parametric experiments of PLSL and their corresponding finite element verifications,variation of the force mode,deformation shape,load-carrying capacity and failure mode of PLSL and wood veneer under mid-span concentrated load were studied.In addition,the influences of magnitude of pre-stress,distribution of screw rod,diameter of screw rod,longitudinal spacing of screw rod,as well as edge distance of screw rod on load-carrying capacity were discussed.The analysis results show that,the failure mode of PLSL gradually changes from the strength failure caused by bending and torsional deformation to strength failure caused by inside plane bending with the increased number of veneers,and the load-carrying capacity is greatly increased.Too large pre-stress and diameter of screw rod as well as too intensive of screw rods lead to the local compressed damage of wood fiber or throughout cracks.However,too small pre-stress and diameter of screw rod as well as too sparse of screw rods lead to significant lateral torsion deflection.So strength of the materials can not be fully exploited.Initial defects such as knots do have serious harm on load-carrying capacity of PLSL.Finally,the pre-stressing recommendations which can be applied to guide the engineering design are put forward based on the parameters of the experiments.