The influence of self-tapping-screws used as transversal reinforcement on short and long-term bond behavior of structural elements and joints in glued laminated timber

在结构和结构设计主席对胶合层压木材承载元件和用螺钉连接和加固的样本进行的各种调查过程中，已经反复表明，垂直于主载荷方向的自攻螺钉的实施作为加固，增加了轴向加载螺钉的粘结性能和结构元件的承载能力。这种加固结构减少了由荷载引起的横向拉应力，特别是由湿度变化引起的粘结界面的收缩裂缝，从而毫无疑问地延长了木质构件的使用寿命。这里提出的研究项目涉及与材料相关的相互关系和自攻螺钉的承载效果，其特别是垂直于纹理被引入木材基体中，以获得用于布置这种类型的螺纹增强件的规则和可能的系统。研究不同气候条件（1 ~ 3级）对轴压螺钉短期承载力和长期响应的影响，将有助于发展实用的设计方法，扩大其在木结构中的应用范围。此外，它将调查在何种程度上横向排列的螺钉可以减少水分引起的裂缝，长期的损害积累的债券和抵消木材生长不规则性的影响。 试验研究（短期拉拔试验和长期试验在三种不同的气候条件下）之间的横向增强和非横向增强的标本进行比较。与材料研究平行，将进行包括各向异性的非线性有限元方法的计算，以便能够在承载行为模拟的背景下描述横向钢筋的机械效应。

In the course of the various investigations on glue laminated timber load-bearing elements and specimens joined and reinforced with screws in the Chair of Structures and Structural Design, has been repeatedly shown that implementation of self-tapping screws, perpendicular to the main load direction as reinforcement, increases bond behaviour of axially loaded screw and load bearing capacity of structural elements. This reinforcement configuration reduces transverse tensile stresses caused by load and especially shrinkage cracks in the bond interface caused by moisture variation, whereby the service life of wooden components can be undoubtedly extended in this way.The research project, proposed here, deals with the material-related interrelationships and the load-bearing effect of self-tapping screws, which are introduced into the wood matrix in particularly perpendicular the grain in order to derive rules and possibly a system for the arrangement of this type of screw reinforcement. The investigations of the influence on the axially loaded screw short-term capacity and long-term response under different climates (service class 1 - 3) will help in development of practical design approaches and expand the range of application in timber structures. Also, it will be investigated to what extent transversely arranged screws can reduce the moisture induced cracks, long-term damage accumulation in the bond and counteract the influence of wood growth irregularities. The experimental investigations (short-term pull-out tests and long-term tests in three different climate conditions) are comparative between transverse-reinforced and non-transverse-reinforced specimens. Parallel to the material investigations, calculations with non-linear finite element methods including anisotropy will be carried out in order to be able to depict the mechanical effect of the transverse reinforcement in the context of load-bearing behavior simulations.