Study On Deformation Characteristics And Optical Fiber Sensor Monitor Measures Of Long-span Prestressed Concrete Continuous Bridge

With the development of Chinese modernization and the rapid development of bridge construction,many large-span prestressed continuous bridges have emerged in the complicated environment including river-crossing,expressway-crossing and railway-crossing.Aiming at uneven settlement,stress concentration and other failure modes in the continuous bridges cantilever construction process,at present,the common finite element software is used to analyze the deformation characteristics of continuous bridges.Most of the papers only analyze the overall deflection and stress of the bridge after the closure of continuous bridges.The simulation analysis of continuous bridges cantilever construction process is relatively few.In the field deflection measurement of the continuous bridges cantilever construction process,the main methods of bridge structure deflection monitoring are traditional monitoring methods and automatic monitoring methods,but most of them can't bring about real-time monitoring and automatic early warning.It can't meet the needs of deformation monitoring of continuous bridges cantilever construction in complex environment.To solve the problem above,this paper takes the Shaba Anning river which is double-track and super-large bridge from Emei to Miyi of Chengdu-Kunming Line 2 as the engineering support.Researching on deformation characteristics and Optical Fiber Sensing Monitoring technology of long-span prestressed continuous bridges.The main research work of this paper is as follows:(1)Establishing the spatial analysis model of continuous bridges in site by using ANSYS finite element software.Simulating different working conditions of continuous bridges cantilever construction by using APDL language and combining the life-and-death function of element.Picking up the deflection and stress at key positions of bridge segments in maximum cantilever stage and different working conditions.Obtaining deflection and stress curves corresponded by using Origin software to analyze and process data.Analyzing the deformation characteristics of long-span continuous bridges theoretically.(2)Designing a Fiber Bragg Grating inclinometer based on pendulum-cantilever structure with equal strength,according to the principle and method of Fiber Bragg Grating sensor.Analyzing the theory of monitor by using the knowledge of material mechanics and structural mechanics.Obtaining the mathematical expression of the wavelength difference ??_B between two fiber gratings in the obliquity meter and the obliquity angle of the obliquity meter ?.Analyzing the related characteristics of Fiber Bragg Grating inclinometer including linearity,sensitivity,hysteresis and repeatability error.The results show that the designed sensor has good performance in all aspects.(3)Building up Fiber Bragg Grating sensing system by using wireless Fiber Bragg Grating demodulator and relevant software system,and applying to reality engineering according to Fiber Bragg Grating inclinometer and the algorithm of deflection of bridge span.Laying the sensors on site optimally,achieving real-time monitoring and on-line early warning for the whole process of cantilever construction of continuous bridges,and obtaining the deformation characteristic curves of continuous bridges during key construction steps and the whole process.Finally,comparing and analyzing the field monitoring data and numerical simulation data.It has certain guiding significance for deflection control of continuous bridges cantilever construction process.This paper analyses the deformation characteristics by numerical simulation method,and application of Optical Fiber Sensing monitoring technology in continuous bridges cantilever construction.Predicting potential danger of engineering and optimizing construction parameters,it can escort the continuous bridges cantilever construction.