| Steel cable-stayed bridges have been widely used in the construction of modern long-span bridges due to their beautiful appearance,large span capacity,and good wind resistance stability,bringing great convenience to people’s lives.However,due to natural erosion and frequent loading,many bridge diseases have occurred in various components of cable-stayed bridges,among which the damage of the stay cables is the most fatal.In the1980 s,cable-stayed bridges built in China have undergone cable replacement construction and varying degrees of maintenance and reinforcement,while the remaining cable-stayed bridges are also facing cable replacement issues.Through field tests and theoretical model calculations,this paper studies and analyzes the mechanical properties of an actual long-span steel cable-stayed bridge,monitors the entire process of its maintenance and reinforcement,and optimizes and analyzes the cable force after cable replacement.The specific research contents are as follows:(1)Summarize the current research status of maintenance and reinforcement of steel cable-stayed bridges at home and abroad,and carry out comparative analysis of disease detection results over the years,cable force testing of stay cables,structural calculations,and other work in combination with an actual long-span steel cable-stayed bridge project.Through data analysis,a replacement scheme is given.(2)The MIDAS CIVIL finite element analysis model is established based on the on-site measured data,and the model is modified.The construction control parameters such as strain increment,cable force of stay cables,main beam linearity,and main tower deflection of the key sections of the bridge are analyzed and compared with the measured data.The entire process of maintenance and reinforcement is monitored to ensure construction quality and safety(3)In this paper,the influence matrix method is applied to optimize the cable force.Through cable replacement and other reinforcement measures,the bearing capacity and structural internal force of the bridge have been greatly improved.(4)For cable replacement engineering of cable-stayed bridges.Based on the grey theory correlation degree analysis,the data group with the highest correlation degree with the target value is given,and the measured cable force value is modified and fitted with the multivariable grey model GM(1,3).At the same time,the cable force value of the first five cables is used to predict the remaining cable force through GM(1,3).Finally,the predicted value of the model output is compared with the measured value,and the result shows that the grey theory model can better predict the cable replacement engineering of the super-long service long-span steel cable-stayed bridge,and the idea that the grey theory can also predict the data series of different observation points with spatial distribution has also been verified.(5)The structural load test is carried out on the strengthened bridge.The test results show that the structural stiffness meets the requirements,the test bridge span structure meets the requirements for the use of the design load(highway class I),and the bridge is linear and smooth.The cable force values of the main bridge stay cables are distributed symmetrically upstream and downstream,and the north and south towers are evenly distributed,and the percentage difference between the measured value and the theoretical value of the cable force is within±5%.The bridge can be put into normal use.The importance and accuracy of construction monitoring are verified again. |
