Behaviour of T-Stub Under Mode 2 and 3 With Hv and Hr Bolts

Abstract

The behavior of the bolts can strongly influence stiffness, strength, and ductility of joints. The current Eurocodes allows using both HV (German type with failure by nut striping) and HR (British-French type with failure by necking of the shank) bolts without making any distinction between them. However, recent studies showed that these two types of pre-loadable bolts are characterized by different ultimate tensile behavior that could lead different joint ductility. The aim of this work is to investigate the influence of the type of pre-loadable bolts on the behavior of T-stubs when it is subjected to mode 2 and 3. To this end, analytical and numerical analyses were carried out. The results show that only in case of the failure mode 3 some differences can be observed between HV and HR.

Simplified Modelling of Failure in High Strength Bolts under Combined Tension and Bending

“…Under these conditions, in the case of HV type, the failure usually occurs by thread stripping (Figure 1a). However, when the same bolt assemblies are subjected to combined tension and bending, the failure mode changes to fracture of the bolt shank in the threaded portion (Figure 1b) [2][3][4]. Mixed shear and axial behaviour are common in bolted connections such as T-stub connections or end plate connections [5][6][7][8].…”

“…The same problem can be highlighted in the connections of replaceable links, where the bolts undergo large deformations (Figure 1b). In the literature there are some models that can be used to reproduce the stripping of the nut for HV bolts or shank fracture for HR bolts [9][10][11][12][13][14], but a model capable of fully capturing the behaviour of HV bolts under combined tension and bending is missing [4].…”

“…The same problem can be highlighted in the connections of replaceable links, where the bolts undergo large deformations (Figure 1b). In the literature there are some models that can be used to reproduce the stripping of the nut for HV bolts or shank fracture for HR bolts [9][10][11][12][13][14], but a model capable of fully capturing the behaviour of HV bolts under combined tension and bending is missing [4]. Much research [4][5][6][7][8][9][10][11][12][13][14][15][16][17] was accomplished in recent years to develop models able to replicate, with a good level of accuracy, the damage and failure of bolts subjected to a specific action such as pure tension or shear [9][10][11][12][13][14], but most of them require the computation of the parameters needed to implement the failure mechanism of the materials and of the joints themselves.…”

“…In the literature there are some models that can be used to reproduce the stripping of the nut for HV bolts or shank fracture for HR bolts [9][10][11][12][13][14], but a model capable of fully capturing the behaviour of HV bolts under combined tension and bending is missing [4]. Much research [4][5][6][7][8][9][10][11][12][13][14][15][16][17] was accomplished in recent years to develop models able to replicate, with a good level of accuracy, the damage and failure of bolts subjected to a specific action such as pure tension or shear [9][10][11][12][13][14], but most of them require the computation of the parameters needed to implement the failure mechanism of the materials and of the joints themselves. Many authors, such as D'Aniello et al [10,11], proposed a simplified approach to model the failure of European preloadable bolts with the calculation of several damage parameters influenced by many factors, such as the diameter of the bolt, the lengths of the thread and shank, etc., but the computation, calibration and use of these parameters in FEM software like Abaqus [18] may require a substantial increase in time and resources in order to perform the analysis, especially in the case of complex assemblies and cyclic tests [9][10][11][12][13][14][15][16]…”