Connections in steel structures play an essential role in the structural stability of the entire construction. This is also true in the event of a fire. The difficulty in designing connections for fire lies in the fact that not only material properties, but also loads applied to the connections change depending on temperature. In addition, the temperature‐dependent decrease in the tensile strength of high‐strength bolts does not coincide with the decrease in shear strength. So far, the influence of combined tension and shear loading on high‐strength bolts has not been studied in detail. This project included carrying out interaction tests on high‐strength bolts of property class 10.9 (fu = 1000 N/mm2). Post‐fire performance was examined in addition to observing the loadbearing behaviour during fire. The examinations were completed with additional material tests. The results were compared with earlier research on the temperature‐dependent loadbearing capacity of high‐strength bolts during and after temperature loading as well as on the loadbearing behaviour of bolts in steel structures under combined tension and shear loads. This investigation contributes to a better understanding of the loadbearing capacity of high‐strength bolts under combined loading during and after a fire.

Purpose This study aims to verify whether the reduction factors for the post-fire performance of Grade 10.9 bolts stated in an earlier study at the TU Darmstadt are also valid for shear and combined tension and shear. Design/methodology/approach Tests on Grade 10.9 bolt sets under combined tension and shear were carried out. The tested bolts were heated and cooled without being stressed by an additional mechanical load before being tested. Findings The test results show that the reduction factors can also be adopted for bolts under combined tension and shear, but the tension-shear-ratio has an influence on the load bearing capacity. Originality/value The post-fire performance of high-strength bolts is of special interest when a building structure is evaluated after an event of fire. In contrast to conventional structural steel, high-strength bolts do not recover their original strength and material properties.

Prior investigations of the load-bearing capacity of bolts during fire have shown differing behaviour between bolts that have been loaded by shear or by tensile loads. A combination of the two loads has not yet been examined under fire conditions. This paper describes a series of tests on high-strength bolts of property class 10.9 both during and after fire under a combined shear and tensile load.

Prior investigations of the load bearing capacity of bolts during fire have shown differing behaviour between bolts that were loaded by shear or by tensile loads. The interaction of the two loads has not yet been examined under fire conditions. This paper describes a preliminary test series on the postfire performance of high-strength bolts of the property class 10.9 under combined tension and shear. The results show that how the bolt is loaded influences the load bearing capacity. It is assumed that this is also true at elevated temperatures. Further, atest set-up for experiments at elevated temperatures and a more detailed test series on the post-fire performance under combined tension and shear is presented.

No abstract