Analysis Of Influence Of Pre-tension On Static Perofrmance And Axial Fatigue Performance Of High Strength Bolts

The connection form of the steel structure includes two types of welding and non-welding.Nodes that are not welded can be distinguished as bolted connections and rivet joints.In order to meet the promotion of prefabricated buildings in China,it is bound to gradually limit the relatively complicated welding connection of the construction process to the stage of factory processing and manufacturing components,and the convenient bolting connection is the preferred method in the construction stage,in which the high-strength bolt connection pair The key factor that distinguishes a node from ordinary bolting due to its good mechanical properties is the application of pre-tension.At present,although there are many theoretical and experimental studies on the connection of high-strength bolted secondary joints for steel structures,the related research and analysis of the effects of pre-tension on its static performance and axial tensile fatigue performance are scarce.In this paper,the research and achievements of pre-tension on the static performance and axial tensile fatigue performance of high-strength bolted joints are as follows:1.Through theoretical analysis of the difference between the bearing capacity and deformation of the secondary joints of friction type and pressure type high-strength bolts,it is shown that the large deformation of the sub-nodes of the high-strength bolts under pressure can not be applied to the direct bearing part connection root cause;2.An analytical method for calculating the thread load distribution of the screw thread under the external load of the shaft is proposed.While obtaining the proportion of the thread bearing distribution of each circle,the necessity of checking the local strength of the thread is explained by a specific example,and the existing checking method is appropriately modified;3.Through theoretical analysis,the effects of different initial pre-tension on the frictional and pressure-type high-strength bolt connection pairs of the steel structure and the static performance of the joints under different conditions of high-strength bolt joints and different plate thicknesses;4.Combining the analytical method of calculating the theoretical stress concentration factor at the bottom of the high-strength bolt thread groove for calculating the steel structure proposed in this paper,the corresponding fatigue notch coefficient value is obtained;5.Based on the basic theory of fracture mechanics and related research results,a set of methods for estimating the fatigue life of high-strength bolted joints for steel structures under the external load of shaft pull cycle is proposed.6.Combined with the estimation method of fatigue life,quantitative analysis of the influence of pre-tension on the tensile strength of high-strength bolt joints and joint shafts of steel structures.7.A design method for high-strength bolt-joining sub-nodes under the action of axial static load and shaft pull-out external load is proposed.