Research On Evaluation Method Of Long-Span Bridge Cable System Based On Various Detection Data

Modern suspension bridges and cable-stayed bridges have become the main types of longspan bridges world-widely because of their outstanding spanning capacity.However,varieties of diseases have appeared due to the rapid growth of traffic volume,the increasing amount of over-loading car and the long-term environmental erosion.Stay-cables are the main loadbearing components of cable-stayed bridges while hangers are vital force transfer components of suspension bridges.Serious diseases of them will change the alignment and internal force distribution of the bridges.In order to maintain and improve the long-term performance of cables and hangers,it is necessary to put forward detection methods of high efficiency and precision,establish a reliabel condition assessment system for stay-cables and hangers,and then formulate effective maintenance measures for them.Taking the detection technologies as the starting point,a tension force test method of cables and hangers based on IBIS-S microwave interferometric radar system is firstly proposed.Application and verification experiment conduted on Puyi Bridge and The Fifth Nanjing Yangtze River Bridge proves that the microwave interferometric radar is capable of measuring tension force of multiple cables at the same time efficiently and without any contact,and the test results are both accurate and reliable.Secondly,a machine vision disease recognition model based on Mask-RCNN is established to dectect the appearance diseases of cables and hagers.A large number of appearance diseases images are used for in-depth learning of the recognition model.After repeate training and validation,the disease recognition model is able to recognize and classify appearance diseases including surface cut,scratch and helical line damage.According to the binary mask output from the recognition model,a quantitative calculation method of disease area based on perspective correction and connected domain statistical algorithm is further proposed.Then,in order to make full use of the various test data of cable and hanger system,an improved condition asseessment method is proposed based on the current evaluation criteria.The evaluation indexes of cable system are optimized and subdivided according to the detection technologies proposed above.By investigating the current evaluation criteria and relevant research,the evaluation standard combining qualitative and quantitative description is put forward for the newly adding evaluation indexes.Finally,the modified assessment method based on various detection data is applied to evaluate the cables and hangers of two cable-supported bridges in service.The results show that the assessment method established in this research can truly reflect the comprehensive technical condition of stay cables and hangers.