Main Cable Dehumidification System Of Long Span Suspension Bridge

Presently the design and construction level of long-span bridges of our country is being upgraded constantly. How to enhance the durability of bridge structures has become a significant technological issue in bridge design and construction.Main cable, one of the most important structure of suspension bridge, is exposed outside long and weathered by all kinds of adverse environmental conditions. Meanwhile, as the main cable can not be replaced, the life of main cable is to affect the bridge service life directly. The research of main cable dehumidification system was carried out by Japanese in 1990s. The system is to decrease the relative humidity inside main cable by inputting dry air and consequently avoid the corrosion of main cable wires. Suspension bridges in China were developed in recent years, so there has not been systemic study on main cable dehumidification system design and construction.Runyang Yangtze Highway Bridge was a key project in our country's '10^th five-year plan'. Its south branch bridge is a suspension bridge, which now ranks the longest span in China and the 3^rd longest in the world. The design service life of the bridge is 100 years. In order to improve the durability of the main cables of Runyang Bridge, dehumidification system was firstly introduced into the main cable anticorrosive protection of long span suspension bridge in China.Firstly, investigations and analysis of the main cable anticorrosion actuality is carried out in this paper. The development as well as the advantages and necessity of main cable dehumidification system is presented.Based on Runyang suspension bridge, the design method of main cable dehumidification system is studied and the main factors to be considered in the design analyzed in this paper. The design of major parameters including air-sending pressure, airflow volume and air-sending length etc. is expatiated. Study and discussion on the capability requirement and type selection of main cable dehumidification equipments is carried out. The monitoring results validates the performance effect of the system and the reliability of the design parameters.