Experimental And Theoretical Study On Uniaxial Tension And Fatigue Properties Of M24 High Strength Bolts In Assembled Steel Structures

As a green energy-saving and environmentally friendly structural system,the fabricated steel structure is widely used in industrial plants,bridges,houses,offshore oil rigs and other structures.Steel structure joint design and its connection scheme are important links in steel structure design.High-strength bolted joints are widely used in the installation and connection of steel structure buildings.Because the highstrength bolt has the advantages of better tightness,better bearing performance,good fatigue resistance,removable,simple and convenient installation,and less deformation than ordinary bolts,it is widely used.However,with the rapid development of fabricated steel structures,various accidents are also emerging,and fatigue damage is one of them.The stress concentration phenomenon is an important reason for the fatigue source of high-strength bolt connection fatigue damage.It has very important practical significance for the study of high-strength bolt stress concentration and fatigue test of steel structure joints.This article relies on the National Natural Science Foundation of China(51578357)hosted by Professor Lei Honggang.The main research contents and conclusions of this paper are as follows:1.Using ABAQUS finite element analysis software,the high-strength large hex head bolts of M24 steel structure were used as the research object,and the highstrength bolts with different thread forms and different external leakage thread numbers were modeled and analyzed to study different thread forms and different external leaks.The effect of the number of threads on the stress concentration factor of high-strength bolt connections.2.The MST Lankmark 370.50 fatigue testing machine was used to complete the normal fatigue test of 14 high-strength large hex head bolts for M24 steel structure.The regression analysis of the normal fatigue test data of 14 M24 highstrength bolts obtained by the test was carried out.SN curve and equation for normal amplitude fatigue of high strength large hex head bolts for M24 steel structures.3.Based on the SN curve obtained from the fatigue test,the corresponding fatigue design method is established.The allowable stress amplitude corresponding to 2×106 is 105.07 MPa,which supplements the fatigue structure details of “Steel Structure Design Standard” GB 50017-2017.Z5 class.4.The Phenom tabletop scanning electron microscope was used to analyze the normal fatigue fracture of 14 M24 steel structures with high-strength bolts,revealing the mechanism of normal fatigue failure of high-strength bolts for M24 steel structures.