Preloaded bolted connections made of stainless steel under fatigue loading in civil engineering structures

在建筑行业中，不锈钢结构和螺栓连接越来越多地被用作钢结构的承重部件，例如桥梁结构，道路交叉口和海岸防护系统，因为它们在侵略性环境中具有优异的耐腐蚀性。虽然过去主要采用奥氏体不锈钢，但近年来奥氏体-铁素体不锈钢（双相）钢的使用也越来越多。然而，由于构件的粘塑性变形行为以及对冷焊影响的担忧，在疲劳加载结构中采用不锈钢预紧螺栓连接迄今为止还不被认为是可行的。由于这些原因，该项目不仅关注疲劳载荷能力，还考虑螺栓组合的原则紧固行为，包括紧固参数，以防止螺栓过早失效。作为进一步的方面，粘塑性变形行为，夹紧包的界面压力，以避免塑性变形，从而最终过高的预载损失被考虑。因此，本应用程序的中心研究目标是发展概念，用于描述和记录在疲劳载荷下，由典型直径范围为M12至M36的奥氏体不锈钢和双相钢制成的金属建筑螺栓组件制成的预加载螺栓连接的载荷和结构相关非线性行为。最终，目标是将这些发现转化为用于建筑行业的不锈钢优化螺栓组件类型的边界条件。为了实现研究目标，计划在上述方面进行广泛的实验，并将通过数值有限元参数研究扩展实验验证的有限元模型。最后，将开发一个描述粘塑性变形行为的分析模型，导出用于建筑行业的不锈钢奥氏体和双相钢夹紧包的界面压力，将预应力螺栓连接的拧紧行为作为制定描述最低延性要求的适当标准的基础。不锈钢螺栓在拉伸和剪切载荷下的疲劳强度将被确定，用于土木工程的预压螺栓组合的优化类型的边界条件将在所得结果的基础上开发。

In the construction industry, structures and bolted connections made of stainless steel are increasingly being used as load-bearing components in steel construction, e.g. in bridge structures, roadway crossings and coastal protection systems, due to their excellent corrosion resistance in aggressive environments. While in the past mainly austenitic stainless steel was used, in recent years austenitic-ferritic stainless (duplex) steel has also been increasingly used. However, preloaded bolted connections made of stainless steel in fatigue-loaded structures have so far not been considered feasible due to ignorance of the expected preload losses as a result of the viscoplastic deformation behaviour of the components as well as fears regarding cold welding effects. For these reasons, the project does not only focus on the fatigue loading capacity, but also considers the principle tightening behaviour of the boltin assemblies including tightening parameters in order to prevent premature failure of the bolts. As further aspects, the viscoplastic deformation behaviour, the interfacial pressure of the clamping package to avoid plastic deformations and thus ultimately too high preload losses are considered. The central research objective of this application is thus the development of concepts for describing and recording the load- and structure-dependent non-linear behaviour of preloaded bolted connections made of metal construction bolting assemblies made of austenitic stainless and duplex steel in the typical diameter range M12 to M36 under fatigue loading for use in the construction industry. Ultimately, the aim is to transfer these findings into boundary conditions for an optimised bolting assembly type made of stainless steel for use in the construction industry. To achieve the research objectives, an extensive programme of experiments on the aspects mentioned is planned, which will be extended by numerical FE parameter studies with FE models validated on the experiments. Finally, an analytical model for describing the viscoplastic deformation behaviour is to be developed, interfacial pressures for clamping packages made of stainless austenitic and duplex steel for use in the construction industry are to be derived, the tightening behaviour of prestressed bolted joints as a basis for developing suitable criteria for describing the requirements for minimum ductility, The fatigue strength of stainless steel bolts under tensile and shear loads will be determined and boundary conditions for an optimised type of bolting assemblies for preloading for use in civil engineering will be developed on the basis of the results obtained.