Research On Suspender Replacement Of In-service Tied Arch Bridge Without Interrupting Traffic

As the service time of tie-arch bridges in service increases,more and more bridges need to be replaced with suspenders.In the early engineering practice,most of the traffic closures were adopted.However,nowadays,with the development of traffic and social economy,it is imperative to replace the suspenders of tied arch bridges without interrupting traffic.Compared with closed traffic,whether the uninterrupted traffic construction has a greater impact on the mechanical properties of the bridge structure and whether the construction can be carried out safely and efficiently has become the key to such issues.In order to solve this kind of problem,relying on Qixia Bridge Suspender Replacement Project,this paper tries to discuss the noninterrupted traffic suspender replacement by means of finite element analysis and field test.The main content and results of the research are as follows:(1)The Midas Civil finite element model of the tied arch bridge was established by using the formal iterative method.In order to provide data reference for the reasonable replacement sequence and replacement scheme of the suspenders,the influence of different suspender fracture conditions on the structural performance of the bridge was analyzed.The analysis showed that the failure of a single boom did not trigger a cascading failure of other booms and did not cause the tie beams to break.The fracture of two adjacent suspenders may cause the tensile stress at the lower edge of the tie beam to exceed the allowable value,resulting in cracks.Asymmetric fractures disrupt the symmetry of bridge structural performance.In the case of a single fracture of the suspenders on both sides,the tensile stress at the lower edge of the tie beam is still within the allowable range and will not crack.Therefore,in order to ensure the structural safety when the suspender breaks and the extreme situation of temporary suspension system failure occurs,simultaneous replacement of multiple suspenders on one side should be avoided,and symmetrical replacement on both sides can be considered.(2)The replacement of the old suspenders of the Qixia Bridge adopts the temporary suspender method,and the Midas Civil finite element model is used to simulate the suspender replacement sequence and tensioning times.Combined with the simulation results and the actual situation of the bridge,the replacement sequence is determined from the middle height of the span to the arch feet on both sides symmetrically.During boom replacement,three equal-step tensions were performed.In order to verify the safety and feasibility of the scheme,the 10#suspender of the middle span and the 5# suspender of the side span were selected for finite element simulation analysis,and the results showed that the scheme was safe and feasible.(3)According to the actual situation of Qixia Bridge,three traffic organization schemes are proposed,and the influence of structural displacement and internal force is analyzed by using the Midas Civil finite element model.The results show that the three schemes are safe and feasible.Based on the characteristics of the traffic flow,the scheme of not retaining the emergency lane,reducing the width of the lane,closing the outermost lane on the construction side,and keeping the total number of lanes unchanged is selected for traffic organization.Based on this lane arrangement scheme,the influence of heavy(over)loaded vehicles on the bridge structure is analyzed.The results show that the overload ratio,vehicle lane position and vehicle speed all affect the vibration and stress changes.The priority of vehicle driving lane position limitation is higher than the control of overload ratio and higher than the control of driving speed.(4)By sorting out and analyzing the monitoring data of Qixia Bridge,the results show that the monitoring data during the suspender replacement process conforms to the corresponding indicators,and the indicators after the suspender replacement also meet the corresponding specification requirements.It shows that the suspender replacement scheme and the traffic organization scheme adopted for the non-interrupted traffic replacement suspender are safe and reliable.Through the comparison and analysis of the inspection data and load test data of the past years before the replacement and the load test data after the completion of the bridge,it is verified that the replacement and reinforcement of the non-stop traffic suspender has a significant effect and is a successful project.On the whole,this project has improved the stiffness,bearing capacity and safety reserve of the bridge,and extended the service life of the bridge.The various data also provide reference for the future daily maintenance,management and overhaul of Qixia Bridge.(5)This paper proposes an information-based online monitoring platform for construction monitoring of Qixia Bridge’s suspender replacement without interrupting traffic.The platform can continuously track and monitor various control indicators,and establish corresponding early warning mechanisms to monitor and manage construction safety.Through the analysis of the monitoring data stored in the background,the reliability of the platform system is verified,and the idea of accurate monitoring for the replacement of non-stop traffic booms is provided.