Multiple-section Rapid Damage Diagnosis Of Bridges Based On BOTDA Technique

Although the load test is a direct and effective method to evaluate construction quality and carrying capacity of the bridge,the following disadvantages prevent its application such as the long time of closing traffic,the complex procedure,the high cost of load test.Therefore,it is of great significance to put forward a practical rapid damage detection method with little interruption for small and medium span bridges.Following the rapid damage detection of bridges based on quasi-static influence line,this study further investigates the application of BOTDA technique for detecting the damage of bridges rapidly.The research status of damage diagnosis of bridges and BOTDA technique's application to actual bridges are summarized systematically,and the defects of the current damage detection method for small and medium span bridges are analyzed emphatically.Based on the existing research results,this study puts forward the general idea of rapid damage detection for small and medium span bridges according to bridge status classification.The issue of rapid damage diagnosis of beam-like and plate-type bridges using the quasi-static displacement influence line is investigated deeply in this study.Aiming at the mode of damage of horizontal ties of bridges,it is proposed that the difference between two displacement influence lines of one section of bridge is more sensitive to this type of damage,which are demonstrated by using the sensitivity calculation and numerical analysis.Therefore,the method based on the difference of displacement influence lines is presented to rapidly diagnose the damage of bridges.This study focuses on the application of BOTDA technique on the rapid damage diagnosis of medium and small span bridges.Under the quasi-static loading condition,a method is proposed to localize the damage zone of bridges by using the stain of multiple-section obtained with BOTDA technique.After this,the ratio of area of strain response before and after damage is presented to rapidly quantify the extent of damage.Finally,the method of the optical fiber laying and data acquisition are investigated experimentally.Under the quasi-static loading condition,the proposed multiple-section rapid damage diagnosis of bridges based on BOTDA technique is verified by using the measured stain response with different damage extent.Meanwhile,aiming at the special mode of damage of horizontal ties of bridge,it is demonstrated that the difference between two displacement influence lines of one section is more sensitive than the displacement influence line at this section of bridge.