Research On Bearing Capacities Of Connections With Partial Threads Inserted Into Plate Holes

At present,experiment and finite element analysis on the bearing capacity of bolt connection structure are researched considering such parameters as the form of plate section,bolt material and bolt strength.However,there is little consideration has been given to the condition that threads insert into plate holes,while studying bolt connections under static shears.The Chinese code for design of steel structure(GB50017-2017)has no regulations on this topic,while the German code for design of steel structures(DIN 18800-1)specifies the design value of bolt shear capacity with threads on the shear plane.Thus,in order to further study the influence of the depth of threaded inserted into the screw holes on the bearing capacities of the connections and to verify whether the calculation method of the code for design of steel structure conforms to the actual conditions,the main research contents include as follow:1.15 bolted connection specimens were tested to obtain the curves of load and displacement,yield loads,ultimate bearing capacities and failure conditions.The results show that when the depth of threads penetrating into the plate holes is less than the plate thickness,there is little effect of shear capacity of bolt connections.However,the shear capacity has obvious decrease when the depth of the thread inserted into the plate hole is equal to the plate thickness(i.e.the thread is on the shear plane).2.In order to provide reference for constitutive model establishment in finite element simulation,normal temperature tensile test was carried out on three steel plate specimens(The elastic modulus E,yield strength f_yand tensile strength f_uof Q345 steel plate are obtained).At the same time,the models of bolt connections were used to establish according to the size of test specimens.The curves of load and displacement,yield load,ultimate bearing capacities and failure calculated by simulation are in agreement with the test results.Meanwhile,the stress variation process of bolts and plates were analyzed.3.Based on the good agreement between the test results and the finite element analysis results,according to the above numerical model establishment method,a large number of numerical simulation is carried out for different parameters.This includes 58 models including ds(the depth),p(pitch),d(bolt diameter),N(number)and type of bolts in bolted connections.4.By comparing the code for design of steel structure in Chinese and Germany,it can be found that the shear capacity of bolted connection with depth of thread inserted into the bolt hole was(0.0t,1.0t),which was not clearly explained in the two specifications.63 numerical models were established through the finite element software ABAQUS.And finite element analysis was made on the bearing performance of the bolted connection with coarse thread commonly used in Chinese engineering.Finally,calculation formulas were proposed.