Bond behaviour of self-tapping screws with continuous threads and long embedment length being used as reinforcement in glue-laminated timber elements - long-term behaviour

点击翻译按钮获取中文摘要

In the course of the current research project, funded by the German Research Foundation (DFG), the bond behaviour of self-tapping screws with continuous threads in glue-laminated timber elements has been systematically investigated under short term loads by means of pull-out and load distribution tests. Through integration of digital photogrammetric methods, it was possible to cover the strain-conditions of the whole anchorage of the screws in different angles to the grain. Therefore, the effect of the anisotropy on the anchorage of self-tapping screws in wood matrix has been visualized.According to the cellular structures and natural (organic) material characteristics of wood, its creeping and shrinkage in varying climates displays not negligible factors of influence, which have significant impact on the load bearing behaviour of the bond matrix of the composite material screw-wood. For this purpose, the investigations on the influence of long term loads have been involved in the primal application, but they have been excluded in the approval. The already conducted experimental inves-tigations should be complemented with further systematic, analytic and numeric analysis of the influ-ence of long term loading on the bond behavior. The investigation is aiming at creating a description of the changes in the bond behaviour under long term loading and cyclic climate changes. The devel-oped design model for the anchorage can thereafter be approved and adopted for long-term loading, thus enabling the simulation of the bond behavior with the finite element method.