The steel structure has the advantages of high material strength,good plasticity and toughness,light weight and convenient installation etc.Between the various components,they can be combined by riveting,welding and bolting.With the development of science,technology and economy,the steel structure has been gradually popularized and applied in China.What's more,The material standards,design specifications and acceptance specifications used are also continuously improved according to actual conditions.For the bolt connection,comparing the steel structure design specifications of China and Germany,it can be found that there are certain differences between the two.The bolt end distance e1,that is,the distance from the edge of the member along the direction of the force to the center of the first row of bolt holes.The Code for Design of Steel Structures(GB50017-2017)has made clear provisions requiring a minimum allowable distance of2d0 and a maximum allowable distance of 4d0 and 8t,and here d0 is the bolt hole diameter,t is the thickness of the steel plate.However,in the German Code for Design of Steel Structure,the minimum allowable distance for the bolt end distance is required to be 1.2d0,and the maximum allowable distance is the smaller of 3d0 and 6t.At the same time,Chinese current code proposes a calculation method for the ultimate bearing capacity of bolted test pieces,but there are fewer factors to be considered,only the thickness t,the bolt type and the steel material.In order to study the mechanical properties of bolted joints under different end distances,two sets of bolted joint species were designed and static load tests were applied on all specimens.And the large-scale general finite element software ABAQUS was used for numerical simulation,and theparametric analysis was carried out by establishing 13 sets of bolted joint plate models with different end distances,the main research contents include:1.Test the two sets of bolted joint specimens,and obtain the load-displacement curves,ultimate bearing capacities,deformation values and failure modes.The results showed,as the bolt end distance increases,the slope of the load-displacement curve rises during the shaping stage,which is manifested by an increase in ultimate bearing capacity and deformation.Among them,the cover plates have two modes of failure: when the end distance is too small,the bolt is torn out from the end of the plate;when the end distance is large,the plastic deformation of the bolt hole is elongated,and the plate is damaged by pressure.2.Using the finite element software ABAQUS to carry out numerical simulation analysis of the test pieces,using the constitutive relation obtained from the material test to calculate the corresponding load-displacement curve,ultimate bearing capacity,deformation value and failure mode,etc.Compare the results of finite element analysis and test,they can be well matched,and the correctness and rationality of the finite element model of the bolted joints are verified.3.Modeling with proven finite element methods,the load-displacement curves and ultimate bearing capacities of the bolted test pieces are obtained,and the finite element results are compared with the values calculated by the Chinese and German steel structure design specifications.It can be found that Chinese regulations are relatively conservative and have high security.The German specification takes into account the influence of geometrical parameters such as bolt end distance and margin,and the degree of agreement with the finite element results is better.4.Parametric analysis of the bolt connection,taking the test results and calculation methods proposed by the Chinese and German steel structure design specifications as reference,changing the bolt margin e2,the spacing e,the line spacing e3,and the number and diameter of the bolts A total of 13 sets of bolted finite element models were establish to study the influence of bolt end distance on the mechanical properties of the test pieces under different conditions.5.According to the difference in thickness,China's steel plates are divided into ultrathin plates,thin plates,medium plates,medium-thick plates and extra-thick plates.For the steel plates of common models,the bolt connection model is established for finiteelement analysis.The mechanical properties of the test pieces are obtained within the range of the allowable values of the bolt end distance between China and Germany: First the minimum allowable distance for the bolt end distance,when the thickness of the plate is t?5mm,the test piece adopts the connection form of single row bolts,Compared with the case where the terminal distance is 2d0,when the end distance is 1.2d0,the ultimate bearing capacity can reach 80% or more at 2d0.When the plate thickness is t>5mm,the test piece adopts the connection form of double rows bolts or multiple rows bolts,compared with the case where the end distance is 2d0,When the end distance is 1.2d0,the ultimate bearing capacity can reach more than 95% when 2d0.Second the maximum allowable distance of bolt end distance,for different types of steel plates,the comparison of the end distance is 3d0 and 4d0 respectively,the differences between the ultimate bearing capacity of the test pieces is less than 5%.Third based on the above results,it is recommended that the bolt end distance is the minimum distance,the allowable value can be relaxed to the range of 1.2d0,but the ultimate bearing capacity should be appropriately reduced in the design calculation,and the proposed calculation formula in the range of 1.2d0?e1?2d0 is proposed.The maximum allowable distance of the bolt end distance is recommended,and the value is in the range of 3d0?e1?4d0,and the value can be appropriately lowered. |