Study On Bearing Capacity And Reaming Performance Of High Strength Bolt Connection Under Different Parameters

Steel structure has been widely used in bridges and buildings due to its advantages of light weight,high strength,high industrialization,environmental protection and good deformation ability.The components of steel structure can be combined by welding,bolt connection and riveting.As a kind of bolt connection,high-strength bolt connection has been paid more and more attention because of its convenient disassembly,large bearing capacity,good elastic performance,simple construction and fatigue resistance.At the same time,although the failure mode of high-strength bolt connection and the influence of hole size on the performance of the structure are gradually improved,there are some deficiencies.At present,there are few factors considered in the design and calculation method of the ultimate bearing capacity of high-strength bolt connection in the domestic code,which is different from other national codes.Moreover,the influence of reaming on the performance of high-strength bolt connection is mostly about friction type,and the influence of reaming on the performance of pressure type bolt connection is very little.In this paper,based on the existing codes and research results,the mechanical properties of pressure bearing bolted connections under different end spacing are studied in depth,and a large number of finite element analysis is carried out on the bearing capacity of high-strength bolted connections under the condition of reaming.This paper mainly completes the following work:(1)Firstly,this paper introduces the research status of the hole enlarging and parametric analysis of high-strength bolt connection,and puts forward the research ideas and methods based on the investigation results.(2)According to the existing domestic and foreign codes,the structural requirements and working performance of high-strength bolt connection are summarized.The calculation methods of ultimate bearing capacity of high-strength bolt connection in three codes of China,America and Europe are analyzed and compared with examples.The calculation results show that: for pressure type high-strength bolt connection,the ultimate bearing capacity of Chinese code is the smallest,and for friction type high-strength bolt connection,the ultimate bearing capacity of Chinese code is the smallest For bolted connection,China and Europe are very close,both of which are less than the value specified in the US code,indicating that China’s code is more conservative.(3)Based on the three-dimensional solid model of pressure type bolt connection with different end spacing established by ANSYS,the ultimate bearing capacity and failure form of high-strength bolt connection are analyzed and studied in detail.The results show that: in a reasonable range,the ultimate bearing capacity increases with the increase of the bolt end distance;with the increase of the bolt end distance,the failure mode of the bolt connection structure transits from the bolt tearing out from the end of the cover plate to the hole wall bearing failure and then to the bolt bar bending deformation failure.(4)Taking the high-strength bolt connection of pressure bearing type as the research object,the finite element model is built by ANSYS,and the size,position,model and construction parameters of the enlarged hole are successively taken as variables,and the influence of different variables on the bearing performance of the connection of pressure bearing high-strength bolt is analyzed.The results show the size and location of the enlarged hole have significant influence on the ultimate bearing capacity,and the different sizes and positions of the enlarged hole can be reduced according to the reduction coefficients of 0.85 and 0.9;the structural parameters and bolt types have little impact on the bearing capacity,as long as they meet the requirements of the code.(5)Taking the friction type high strength bolt connection as the research object,the finite element model is established,and the size and position of the enlarged hole are taken as variables to carry out the parametric analysis of the sliding load of the bolt.The results show that the influence of the size and location of the enlarged hole on the sliding load is more significant.The sliding load can be reduced according to the reduction coefficient of 0.85 for the different sizes and locations of the enlarged hole.(6)The bearing capacity of friction type and pressure bearing type high-strength bolt connection under different plate thickness is studied by ANSYS.The results show that the ultimate bearing capacity of pressure type high-strength bolt connection structure is related to the plate thickness,while the ultimate bearing capacity of friction type high-strength bolt connection structure is not related to the plate thickness;under the condition of the selected cover plate thickness in this paper,the bearing capacity of friction type high-strength bolt connection is large when the plate thickness is 12 mm or less,When the thickness is more than 12 mm,the bearing capacity of the bearing type is large,and gradually increases with the increase of plate thickness and then tends to be stable.