Structural Performance of Timber Connections with Long Self Tapping Wood Screws

长自攻木螺钉（STS）是近年来欧洲的一项重要发明，旨在增强木材的固有弱点，如垂直于纹理的拉伸和压缩强度以及纵向剪切强度。 这些螺钉在欧洲广泛用于加固遭受过度开裂的大型木材/胶合木梁。除了加固作用外，这些螺钉还可用于在木结构连接中提供主要的荷载传递。 在N.在美国，这些螺钉还没有普及;方头螺栓的规范条款与STS的应用最相似。 然而，这些规定忽略了这些连接件的最重要特征，即，它们的拔出能力和与木纹成一定角度的刚度;因此，这些规定是不适当的。 在欧洲为不同品牌的专利STS产品开发了广泛的STS数据库，每个品牌都有自己的技术批准，主要适用于欧洲物种（云杉和松树）。 对欧洲设计规定的初步评价表明，它们不适用于N。美洲树种的木材中的节结构和密度范围与欧洲木材有很大不同。 此外，还没有关于这些螺钉在单板层积材和平行胶合板等结构复合木材应用中的应用的信息;因此，需要开展大量工作来了解STS在N.美国参考

Long self-tapping wood screw (STS) is an important recent European invention intended to reinforce the inherent weaknesses of wood such as the tension and compression perpendicular to the grain strengths and longitudinal shear strength. These screws are widely used in Europe to reinforce large timber/glulam beams that have suffered from excessive cracking. Besides the role of reinforcements, these screws can also be used to provide primary load transfer in timber connections. In N. America, these screws are not yet popular; code provisions for lag bolts have the closest resemblance for the applications for STS. However, these provisions ignore the most important feature of these connectors, namely, their withdrawal capacity and stiffness applied at an angle to the wood grain; therefore, these provisions are not appropriate. The extensive database developed in Europe on STS for different brands of proprietary STS products, each having its own technical approval, can be applied mainly to European species (Spruce and Pine). Preliminary evaluation of the European design provisions indicates that they are not suitable for N. American species where the knot structures in the wood and density range are very different from European wood. Also there is no information on the application of these screws in application of structural composite lumber such as laminated veneer lumber and parallel strand lumber; therefore, significant work is needed to understand the behaviour and quantify the performance of STS for applications in N. America.