Nailplates are widely used in domestic and low-rise residential housing markets and have begun forming part of mid-rise developments. There is however a concern about nailplates backing out which has been observed in a variety of conditions. In-service backouts in excess of 2 mm have been recorded and can result in up to a 50 % reduction in joint performance. The amount of backout varies significantly from roof space to roof space and the physical phenomena leading to backout and their exact relationship to the climatic conditions are largely unknown. This paper experimentally investigates the time dependent backout mechanisms and develops a numerical model to predict the range of backouts that will be expected from a set of climatic conditions that the nailplates would be exposed to. Specifically, this paper initially investigates the backout of single nails, representative of nailplate teeth, by pressing the nails into pieces of timber and subjecting the samples to cyclic climatic conditions. The moisture driven backout of the nails was monitored in real-time using Digital Image Correlation for 48 days. Backouts of between 0.08 and 0.26 mm were observed. Results showed that during the drying phase, the timber surface tended to slide along the surface of the nail. A similar phenomenon was observed during the wetting phase but to a lower extent. This consequently led to a ratcheting mechanism that caused the nail to backout from the timber. A numerical model is then proposed to predict and replicate the time dependent backout behaviour of the nailplate tooth based on heat and mass transfer algorithm TransPore and Finite Element Software ABAQUS. The model was validated against the experimental results based on the timber properties and climatic conditions that the timber was exposed to. The model was able to accurately predict the time-dependent backout of the nails. To illustrate the application of the model, the expected nailplate backout for two different Australian roof spaces was investigated. A variety of parameters was investigated including the length and position of the tooth. It was found that longer teeth experienced higher rates of backout and significant variations in backout were encountered whether the tooth is closer to the edge or the middle of the timber.

钉板广泛用于国内和低层住宅市场，并已开始成为中层开发项目的一部分。然而，人们担心在各种条件下都观察到钉板退出。已经记录了超过 2 毫米的使用中回退，并可能导致接头性能降低多达 50%。不同屋顶空间的倒塌量差异很大，导致倒塌的物理现象及其与气候条件的确切关系在很大程度上是未知的。本文通过实验研究了时间相关的回弹机制，并开发了一个数值模型来预测钉板将暴露于一组气候条件下的回弹范围。具体来说，本文通过将钉子压入木材块并使样品处于循环气候条件下，初步研究了代表钉板牙齿的单个钉子的脱落。使用 Digital Image Correlation 实时监测受潮导致的指甲脱落，持续 48 天。观察到 0.08 和 0.26 毫米之间的回缩。结果表明，在干燥阶段，木材表面倾向于沿着钉子表面滑动。在润湿阶段观察到类似的现象，但程度较低。因此，这导致了棘轮机制，导致钉子从木材中退出。然后提出了一个数值模型来预测和复制基于传热和传质算法的钉板齿的时间相关回退行为 代表钉板牙齿，通过将钉子压入木块并使样品经受循环气候条件。使用 Digital Image Correlation 实时监测受潮导致的指甲脱落，持续 48 天。观察到 0.08 和 0.26 毫米之间的回缩。结果表明，在干燥阶段，木材表面倾向于沿着钉子表面滑动。在润湿阶段观察到类似的现象，但程度较低。因此，这导致了棘轮机制，导致钉子从木材中退出。然后提出了一个数值模型来预测和复制基于传热和传质算法的钉板齿的时间相关回退行为 代表钉板牙齿，通过将钉子压入木块并使样品经受循环气候条件。使用 Digital Image Correlation 实时监测受潮导致的指甲脱落，持续 48 天。观察到 0.08 和 0.26 毫米之间的回缩。结果表明，在干燥阶段，木材表面倾向于沿着钉子表面滑动。在润湿阶段观察到类似的现象，但程度较低。因此，这导致了棘轮机制，导致钉子从木材中退出。然后提出了一个数值模型来预测和复制基于传热和传质算法的钉板齿的时间相关回退行为 通过将钉子压入木块并将样品置于循环气候条件下。使用 Digital Image Correlation 实时监测受潮导致的指甲脱落，持续 48 天。观察到 0.08 和 0.26 毫米之间的回缩。结果表明，在干燥阶段，木材表面倾向于沿着钉子表面滑动。在润湿阶段观察到类似的现象，但程度较低。因此，这导致了棘轮机制，导致钉子从木材中退出。然后提出了一个数值模型来预测和复制基于传热和传质算法的钉板齿的时间相关回退行为 通过将钉子压入木块并将样品置于循环气候条件下。使用 Digital Image Correlation 实时监测受潮导致的指甲脱落，持续 48 天。观察到 0.08 和 0.26 毫米之间的回缩。结果表明，在干燥阶段，木材表面倾向于沿着钉子表面滑动。在润湿阶段观察到类似的现象，但程度较低。因此，这导致了棘轮机制，导致钉子从木材中退出。然后提出了一个数值模型来预测和复制基于传热和传质算法的钉板齿的时间相关回退行为 观察到08和0.26mm。结果表明，在干燥阶段，木材表面倾向于沿着钉子表面滑动。在润湿阶段观察到类似的现象，但程度较低。因此，这导致了棘轮机制，导致钉子从木材中退出。然后提出了一个数值模型来预测和复制基于传热和传质算法的钉板齿的时间相关回退行为 观察到08和0.26mm。结果表明，在干燥阶段，木材表面倾向于沿着钉子表面滑动。在润湿阶段观察到类似的现象，但程度较低。因此，这导致了棘轮机制，导致钉子从木材中退出。然后提出了一个数值模型来预测和复制基于传热和传质算法的钉板齿的时间相关回退行为TransPore和有限元软件ABAQUS。该模型根据木材特性和木材所暴露的气候条件与实验结果进行了验证。该模型能够准确预测指甲随时间变化的情况。为了说明该模型的应用，研究了两个不同的澳大利亚屋顶空间的预期钉板回退。研究了各种参数，包括牙齿的长度和位置。发现较长的齿经历更高的回缩率，并且无论齿更靠近木材的边缘还是中间，都会遇到回缩的显着变化。