Research On Cable Force Control Of Strand Stayed-cable

In recent years,parallel strand as a common material of cable-stayed bridge is used more and more widely,because it possesses great advantages in fabrication,installation,stress characteristics and economy.Comparing with parallel steel stayed-cable,it is difficult to measure and control the cable force precisely.Therefore,it is necessary to conduct an analysis and research on the control of cable force in the construction process of the strand stayed-cable bridge.This thesis takes Xiliu Bay Bridge in Yiyang City,Hunan Province as the project background,and the main research contents are as follows:(1)The construction method and technology of parallel strand stayed-cables are introduced in detail.Considering the influence of permanent load on cable force caused by synchronous construction of main girder during cable installation,the first tensioning method of cable is supplemented,so that the cable force in the construction process can be in line with the actual situation and get rid of the errors caused by construction.(2)Some cable-stayed cables of Xiliu Bay Bridge as the research object are selected,and Midas Civil software is used to establish the coupling model of each stayed-cable and its pipe,and the contact between HDPE casing and cable-stayed by adjusting parameters is simulated,and then the influence of stayed-cable pipe on the natural vibration frequency of cable-stayed under different contact conditions is analyzed.(3)After the bridge is finished,the outer HDPE sleeve has been installed in place and the acceleration sensor can only be bundled on the HDPE sleeve to measure the vibration frequency,so the vibration frequency of the internal stayed-cables can not be measured directly to calculate the cable force.In the past,measurements were made at the end of the main beam,and the results were not very accurate.Therefore,a new measurement method is proposed in this thesis,selecting the section near the middle of the cable for measurement,and collecting the vibration frequency of the HDPE sleeve on site.The feasibility of this measurement method is analyzed,which is compared with the theoretical calculation frequency.(4)Considering the influence of temperature,the existing formulas for calculating the tension of steel strand cables is corrected.A finite element model is established to analyze the influence of cantilever length on the uniformity of cable force of steel strand cable during the construction of main girder,and the influence of synchronous construction on the uniformity of cable force on the hanging basket is analyzed,and the related correction method is proposed.