The main bridge of Longtan Changjiang River Bridge is a suspension bridge featuring a suspended main span of 1 560 m and two side spans of 615 m and 552 m,with the stiffening girder in the suspended main span consisting of steel boxes.Each of the two main cables contains 126 strands,and a single strand is composed of 127 parallel steel wires of 6 mm diameter and a nominal tensile strength of 1 960 MPa.The bridge is fitted with a dehumidification system for main cable corrosion protection,which consists of air blowers,airflow conduits,exhaust clamps and humidity monitors.Dried air flows through the conduits embedded in the center of the main cable to take away the damp,thereby delaying the corrosion of the steel wires.This study investigates the dry air pressure distribution along the airflow conduits and presents the test results of the dehumidification system on a main cable mockup,as well as the selection of an effective perforation scheme for the airflow conduits.In the Longtan Changjiang River Bridge,exhaust sleeves are spaced 45 m in the airflow conduits,and each exhaust sleeve contains 6 circular air outlets of 4 mm diameter to achieve effective dehumidification protection for the main cables in the center span.The dehumidification system supplies dry air that is sufficient to cover the full cross-section of the main cables,with the sustained supply of dry air,the relative humidity at each monitored points inside the main cables drops below 50％,indicating that the dehumidification system achieves the expected dehumidification effect.The engineering practice in the Longtan Changjiang River Bridge proves the manufacture and installation accuracy of the airflow conduits,and the effectiveness of the perforation scheme.
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