Experimental Study On The Mechanical Behavior Of Q690 High Strength Steel Bolted Connection

The diversification of architectural forms has led to the development of new highefficiency,energy-saving and environmentally friendly high-strength steel products.High-strength steel has been used in domestic and foreign construction and bridge projects.The high strengthening and assembling trend of building steel structure has higher requirements on connection performance.High strength steel bolted connections have a complex force.The bolt number of bolted connection is large,resulting in a larger range of bolted connection.And there is currently no design provision for high-strength steels in domestic specifications.In order to understand the mechanical behavior of high strength steel bolted connections,promote the application of high-strength steel,especially the application of domestic high-strength steels.In this paper,the experimental study on the mechanical behavior of Q690 high strength steel bolted connection were carried out.At the same time,comparative tests of Q345 steel bolted connection were carried out.The main research work and achievements of this paper are:(1)The material test of Q690 steel,Q345 steel,grade 10.9 and 12.9 high strength bolt with large hexagon head was conducted.A test on the torque coefficient of seven type high strength bolts was conducted by batch.The static test of the 77 high-strength bolted connections was completed,and the load-displacement curve,ultimate bearing capacity and peak displacement of the bolted connections were obtained.(2)Through analysis of the test data,the local deformability of Q690 high-strength steel was studied.And the influence rules of the strength and thickness of the steel,the bolt size,the pretension of the bolt,the bolt arrangement,and the geometry of the panel on the failure mode,ultimate bearing capacity and deformation of the bolted connections were obtained.(3)The test data and the calculated value and predicted failure mode of the different steel structure specification were compared,and the difference and the reasons have been pointed out.The optimized boundaries among the transition of failure modes were proposed,which are in good agreement with the test results.The grading problem of bolt and steel was discussed.(4)Summary analysis of the test data of high-strength steels bolted connections of some scholars,the relationship between bearing capacity and end distance of highstrength steel bolted connections with tear out failure was obtained.The difference of bearing capacity between tear out failure and splitting failure of high strength steel bolted connection was compared.Based on the test and analysis,this paper points out existing problem in the relevant regulations of GB50017-2003 about bearing-type connections,and puts forward some suggestions for modification.The innovation of this paper:(1)The experimental study on the bolted connection made of domestic high-strength Q690 and grade 12.9 high strength bolts was carried out.(2)The pretension was applied to grade 10.9 and 12.9 high strength bolts with the measured torque coefficient,and the influence of pretension on bolted connections was studied.(3)The failure modes relationship of single bolt shear connection was analyzed.The optimized boundaries among the transition of failure modes were proposed.