Investigation of the Effects of an over‐elastic Preload on the load‐bearing Behavior of high‐strength Bolt and Nut Assemblies

Abstract

AbstractCost efficiency and sustainability of construction measures are determined not only by the cost of the new building itself, but also by subsequent improvements and running costs. This also includes the cost of replacing bolts that were not installed in accordance with the requirements given in the decisive specifications. Here, the subsequent control of the assembly is specified. Accordingly, preloaded bolts have to be checked for overtightening. If a bolt is classified as overtightened, this can result in the entire bolt group having to be replaced under supervision. In addition to the high cost of replacement, this often means that further work has to be temporarily halted. However, there is a lack of knowledge about the degree of utilization of the bolt defined as overtightened and the influence on the microstructure of the material as well as on the load‐bearing behaviour. The results of first experimental investigations suggest that over‐elastic preload forces only have a significant influence on the load bearing behaviour of high‐strength bolts when exceeding a certain point. The assessment of preloaded bolts with respect to overtightening as given in specifications seems to be too general – and for the bolt lengths so far investigated too conservative.