To effectively control the delayed fracture of high-strength bolts in steel bridges,numerical simulation together with experimental research were conducted to analyze the fracture causes and the measures to improve the anti-delayed-fracture performance of the steel for high-strength bolts.An axial tension control technique is proposed.It is shown that the occurrence probability of delayed fracture of high-strength bolts is narrow,but critical,which should be controlled as much as possible.The fracture mainly occurs in the stress concentrated zones in the junctures between the head and straight rod,straight rod and screw rod,and screw rod and screw nut.Overtightening of the bolt would remarkably increase the delayed fracture risk,and the high strength and sensitivity to hydrogen embrittlement as well as stress concentration are considered the main causes of the hydrogen-induced delayed fracture.It is suggested to improve the limit tensile strength of the Grade 10.9 steel for the high-strength bolts to 1 190 MPa.The application of SRQS1 steel can effectively enhance the anti-delayed-fracture performance of the bolt.An intelligent bolting control system for the steel bridge is developed.An ultrasonic wave based method to measure the axial forces of bolts in existing bridges is proposed,with the intent of achieving the accurate monitoring and control of axial forces of the bolt at both the construction service stages of the bridge.
关键词
钢桥/高强度螺栓/延迟断裂/智能管控系统/轴力测试方法/现场调研/有限元法/试验
Key words
steel bridge/high-strength bolt/delayed fracture/intelligent control system/axial force measurement method/field survey/finite element method/test
维普
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