Study On The Mechanical Behavior Of Friction-type High-strength Bolts Under Tension And Shear At High Temperature

With the rapid development of the steel structure,the friction type high strength bolt has been widely used in the connection of the steel structure.Due to the poor fire resistance of the friction type high strength bolt,its bearing capacity will be greatly decreased at high temperature.As a results,the friction type high strength bolt will gradually lose its function in the steel structure.Under the high temperature environment,the friction type high strength bolt is mainly bearing tension stress and shear stress.However,the studies and researches about combined tension stress and shear stress has not been developed.Therefore,further research on stress state under high temperature has important theoretical significance and practical value.In this paper,the mechanical properties of friction type high strength bolt in the combination of tension and shear are studied based on finite element method software ABAQUS.According by establishing the friction high strength bolt on connection steel structure of the finite element model,the temperature regression formula of the friction type high strength bolt has been established.The main contents of this paper are as follows:(1)Through the comparison of national standards,for steel structure material thermal expansion coefficient,thermal conductivity and specific heat of thermal performance parameters and Poisson's ratio,the equivalent yield strength and modulus of elasticity of the related parameters of mechanical properties were introduced,these parameters with the temperature changes and their effective temperature interval list,for the finite element analysis provides for the constitutive relationship on the basis of the theory.Moreover,the creep of the steel structure is introduced,which provides a reference for the temperature loading.The different loading forms of temperature field and different temperature rising curve were analyzed,and the method of temperature field was determined,which provided the basis of the temperature field for the finite element analysis;(2)Because of the complexity of the test model,the model is simplified to a certain extent.The element model is established which ignore the effect of the bolt and combined tension and shear stress state under the high temperature.According to the parameters of the structural material introduced in the second chapter,the stress state of the bottom plates(including different thickness plates,different tension and shear stress)was calculated.It proves that the finite element model is correct and the calculation results are reliable to compare with the experiment results.Based on calculated results,the stress state of the node was analyzed which provide necessary data for the following single bolt analysis.(3)According to the stress state results of the single bolt,and loaded the data of the single bolt into the single bolt,the finite element model of the single friction type high strength bolt has been established.Using the finite element calculation of the single friction type high strength bolt,the stress of the bolt joint was analyzed in detail.(4)By means of SPSS software for data regression analysis,combined with the current standard of steel structure GB50017-2014 proposed reduction coefficient and regression formula of reduction coefficient was derived.Finally,according to regression analysis curve to verify its effectiveness.