Study On The Vulnerability And Hanger " Fail-safe " Mechanism Of Self Anchored Suspension Bridge Based On The Instantaneous Dynamic Process Break Of Hanger

As a key component of a self anchored suspension bridge,hangers may suddenly break under the action of fatigue and corrosion,endangering the safety of the bridge structure and causing serious consequences.At present,there is a lack of research on the structural vulnerability of the self anchored suspension bridge after hanger breakage and the measures to prevent hanger breakage.Taking a self-anchored suspension bridge as an example,this paper analyzes the structural vulnerability of the self-anchored suspension bridge with different hanger forms after hanger breakage using the importance coefficient method;and proposes to use the "fail-safe" hanger to improve the dynamic response of the structure after hanger breakage and verify the effectiveness of the "fail-safe" based on model tests.The main research contents and results are as follows:(1)Based on some typical cases of broken hangers at home and abroad,the necessity of the research on the structural vulnerability of the self-anchored suspension bridge after hanger breakage and the practical significance of the research on the "fail-safe" hanger are pointed out,and the current status of domestic and foreign researches are introduced.(2)Based on the impact effect on the structure after hanger breakage,the research method of the hanger breakage of the self-anchored suspension bridge is discussed,including determining the semi-dynamic analysis method as the analysis method of the impact of the hanger breakage on the structure and defining several necessary parameters in the numerical analysis;based on the existing structural vulnerability theory,the analysis methods of the vulnerability of the self-anchored suspension bridge are discussed,including the analysis of the applicability of the sensitivity analysis method,plastic limit state analysis method and importance coefficient analysis method and determining the use of importance factor method to analyze the structural vulnerability;the hanger "failsafe" mechanism is put forward,including explaining what is the "fail-safe" hanger and describing several common forms of "fail-safe" hanger and their construction method.(3)Based on the actual project,the hanger breakage response analysis of selfanchored suspension bridges with different hanger forms is carried out.The results show that the hanger breakage of the self-anchored suspension bridge with a single hanger will only affect the cranes with the same span and has the most significant impact on the cable on the immediately adjacent hanger and small impact on the main tower,the main beam and the main cable.The use of "fail-safe" hanger can effectively improve the response of the hanger adjacent to the broken hanger;through the evaluation of structural vulnerability based on the response analysis of the structure after the hanger breakage,it is found that the vulnerability coefficient of the adjacent hanger after the hanger breaks may be more than 1 for the self-anchored suspension bridge with a single hanger,which does not meet the requirements for continuous bearing.However,with fail-safe hanger,the coefficient of the adjacent hanger has a significant reduction and is less than 1,and the vulnerability coefficient of the "fail-safe" hanger is less than 1.(4)Based on the model test,the improvement of the dynamic effect of the structure after the hanger breakage by "fail-safe" hanger is verified.The test results show that the use of the "fail-safe" hanger significantly improves the impact of the broken hanger on the adjacent hanger,and the peak value of response of "fail-safe" hanger is smaller than that of the immediately adjacent hanger after a single hanger breaks.