Study On Sheared High-strength Bolted Connections Fabricated Of Highperformance Fire-resistant Steel At Elevated Temperature

With the increasing use of steel structures in structure engineering,the problem of fire protection becomes more and more serious.The strength and stiffness of steel will decrease rapidly at elevated temperature,so steel structure buildings are easy to be destroyed in fire.In this context,many countries began to carry out the research and production of fire-resistant steel,some of the fire-resistant steel has been used in building construction.Wuhan Iron and Steel(Group)Company developed WGJ high-performance fire-resistant steel in 2016,and Shougang Group developed BFRW10 high-strength fireresistant bolts in 2018.They not only meet the requirements of material properties at room temperature in the specification,but also have good fire-resistant property.Based on these two kinds of material,through the way of combining experimental research and numerical analysis,this paper explore the material performance of BFRW10 fire-resistant highstrength bolts under room temperature and elevated temperature,and shear performance of sheared high-strength bolted connections fabricated of high-performance fire-resistant steel at elevated temperature.On this basis,this paper put forward the calculation formula of the reduction factor of shear bearing capacity of bolted connections fabricated of highperformance fire-resistant steel and high-strength fire-resistant bolts at elevated temperature.The main work of this paper includes the following parts:(1)The material properties of BFRW10 fire-resistant high-strength bolts were tested at room temperature and elevated temperature.The mechanical properties were measured and the stress-strain relationship and the reduction coefficient of strength and stiffness were given.A conclusion can be drawn by comparison: the BFRW10 fire-resistant highstrength bolts have good fire-resistant property.(2)The shear tests of 24 bolted joint fabricated of different types of high-strength bolts were carried out under different temperature groups,including 18 members using ordinary high-strength bolts and 6 members using high-strength fire-resistant bolts,and the connection plate was manufactured of WGJ high-performance fire-resistant steel.The friction coefficient of friction surface at room temperature,load-displacement relation,load reduction factor and failure mode of the bolted connections under different temperature were studied.It is found that the slip load and ultimate load of bolted connections decrease with the increase of temperature.The reduction factor of slip load and ultimate load of the bolted connections fabricated of fire-resistant high-strength bolts are greater than those fabricated of ordinary high-strength bolts at different temperatures.At the same time,with the increase of temperature the failure mode of the bolted connections also changed.(3)The finite element models of sheared bolted connections were established with ABAQUS software,and were compared with the test results in this paper to verify the reliability of the finite element models.On this basis,a total of 108 finite element models were established with different parameters of the specimens,to investigate the influence of bolt grade,bolt diameter,connection plate thickness on the shear performance of the bolted connections at different temperature.Based on these research results,the calculation formula of the reduction factor of shear bearing capacity of bolted connections fabricated of high-performance fire-resistant steel and high-strength fire-resistant bolts at elevated temperature and the shear design suggestions of the connections was put forward.