<p> The Yongjiang Railway Bridge carrying 2-lines heavy-load railways is a steel-concrete mixed box girder cable-stayed bridge with the span arrangement of 53 50+50+66+468 66+50+50+53 m. The stiffening girder is a closed and streamlined box girder with two materials longitudinally: the center 419m of main span is steel box girder installed by deck cranes and the rest of the girder is site-cast concrete box girder.</p><p> Considering that the railway bridge possesses characteristics of carrying heavy railway live load, high requirements for the stiffness of the whole structure, fixed railway tracks, an innovative concept of the structural system for long-span railway bridges is carried out, and three Innovative Technologies is obtained including orthotropic steel deck stiffened by V-shaped ribs, steel-concrete joint with ladder-shaped concrete filled in and frontal/ posterior compression-bearing plates, bilateral–bearing-load cable-girder steel anchorage box. The experimental research proves that orthotropic steel deck stiffened by V-shaped is superior in fatigue behaviour, the proposed new types of steel cable-girder anchorage box and steel-concrete joint both have good performance in the force transferring and fatigue properties. And also vehicle-bridge coupling vibration analysis also shows that the steel-concrete joint achieves smooth transition of stiffness and the trains run smoothly.</p>

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To analyze the time-varying temperature field distribution pattern of ballastless track steel-concrete composite box girders for a high-speed railway at ambient temperature, a numerical model for analyzing the time-varying temperature field of steel-concrete composite box girders was established based on the long-term monitoring data for the internal and external environments of the main girder of the Ganjiang Bridge on the Nanchang-Ganzhou high-speed railway. The influence of factors such as the deck pavement and the ambient wind speed on the time-varying temperature field of the steel-concrete composite box girders were considered. The results showed that there was a significant difference in the vertical temperature gradient patterns on sections at the side web and at the middle web at the same moment in time due to the hindering effect of the track board on the heat exchange between the ambient temperature and the main girder. Increasing the wind speed accelerated the rate of heat exchange between the main girder surface and the environment. In particular, when the internal temperature of the girder was higher than the ambient temperature, the higher the wind speed was, the larger the temperature gradient was. This study lays a foundation for accurate analysis of the structural response of ballastless track steel-concrete composite girder bridges at ambient temperature.

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