A Fundamental Study about the Design of Impact Fatigue Strength for Metal-fastener Joints of Wood-based Board Construction

本文首先研究了冲击载荷作用下的加速度脉冲和应变的基本响应行为，然后研究了冲击载荷重复作用下节点响应行为的转变和节点刚度的降低过程。在不同的接缝条件下，制备了胶合板、定向刨花板、刨花板和中密度纤维板之间以及人造板与框架材料(木材)之间的典型接缝(钉钉和木螺钉)的简化模型。首先，对典型人造板结构的H型接缝试件进行了静力弯曲试验和声发射测试，结果表明，作为典型人造板结构的简单模型，接缝的微小破坏过程与接缝刚度的降低和梁中的应力分布密切相关。在IM…中通过接触弯曲试验，分析了节点刚度对梁应变分布的影响，以及冲击荷载水平对节点刚度的影响。通过对两端弹性支承梁力学模型中应变分布(弯矩分布)的分析，建议用梁的节点处和梁的1/4点处的应变量来评价节点的刚度。其次，对剪力墙钉节点的简单模型--各种人造板在主体构件(框架)两侧用钉子连接的压力型剪切试件进行了静力和重复冲击试验。结果表明，在本试验所用钉子长度不变的情况下，侧梁厚度存在最佳值。由于钉子小腿周围构件的不可逆压缩变形导致木材致密化，滑移量的增加率随侧梁的种类和冲击载荷的大小而有较大的减小趋势。在反复冲击载荷作用下，构件间松动、节点刚度降低等疲劳过程在很大程度上取决于侧梁的种类、厚度和冲击载荷的大小。较少

In this research, first, the fundamental response behavior of the acceleration pulse and strain developed by impact loading were investigated, and secondly the transition of the response behavior and the decrease process of joint stiffness with the repetition of impact loading were examined. For the experiment, some simplified models of typical joint (nail and wood screw) between various wood-based boards such as plywood, oriented strand board, particleboard, and medium density fiberboard or between wood-based boards and frame materials (wood) were prepared under various joint conditions.First, static bending test with AE (Acoustic emission) measurement was carried out for H-figured joint specimen of particleboard jointed with wood screw as a simple model of a typical wood-based board construction.As a result, itwas evident that the minute destruction progress in the joint, the decrease of joint stiffness and the distribution of stress in the beam were closely related each other. In im … More pact bending test, both the influences of joint stiffness on strain distribution over the beam and of the impact load level on the joint stiffness were elucidated. It was suggested that the amount of the strain in the joint point and the quarter point of the beam was available for the evaluation of the joint stiffness, as a result of analyzing the strain distribution (moment distribution) in the mechanical model of the beam elastically supported at both ends.Secondarily, the static and repetitive impact tests were carried out for the compression type shearing specimen, in which various wood-based boards were connected with nail to both sides of the main member (frame), as a simple model of nailed joint in shear wall. The following results were obtained ; it was evident that the optimum thickness of side member were existed, when the length of nail was constant as used in this experiment. The rate of increase in amount of slipping displacement tended to decrease largely, depending on the combination of the kind of side member and the magnitude of impact load, because of the densification of wood due to the irreversible compressive deformation of members around shank of nail. It was also confirmed that the fatigue process, such as loosening between both members and decreasing of stiffness of joints subjected to repetitive impact loading, depended to a great extent upon the kind and thickness of side member and the magnitude of impact load. Less