Distribution of the friction coefficient in the tension connections by the HV set using the combined method

Abstract

AbstractThe use of bolts in steel structures nowadays is one of the cheapest, fastest and easiest solutions for joining elements. HV high‐strength bolts used in tension connections are a special type of fasteners covered by supervision beginning with the selection of the material from which they will be made through the production process and quality confirmation, ending with clearly defined assembly requirements.The tests were focused on two assortments of M16 and M24 bolt assemblies made according to EN 14399. A test of the suitability of the connection was performed, expanding it with tests of the coefficient of friction on the bolt thread and between the nut head and washer according to EN ISO 16047. The dynamic joint load tests showed that the distribution of the coefficient of friction on the thread and between the nut and the washer affects the degree of tension through the preloading force.Tensile tests were carried out on the both aforementioned assortments. The determined yield point of the bolt was analyzed, which was referred to the stress causing plastic deformation in the test of connection suitability. Bolts in two systems of forces were compared with each other (simple ‐ stretching and complex ‐ stretching and torsion) and the difference between them was shown. Based on the correlation of results from both tests, the importance of the K‐factor on the mechanical properties of the HV set was emphasized. The dependence of the K‐factor on the coefficients of friction in a bolted joint has been demonstrated.HV high‐strength bolt sets consider assembly procedures using a combined method according EN 1090‐2. Cases of exceeding the yield point of the bolt during assembly and permanent deformation of the fastener have been shown. The scope of assembly was determined in the elastic range and the transition to the range of plastic deformations. Again, reference was made to the coefficient of friction and its effect on the difference in the obtained preloading force leading to risky assembly in the plastic range.