Study On The Fast Cooling Measures At Prefabrication Stage Of Simply-supported Box Girder Used In High-speed Railway

At the prefabricated stage of simply-supported box girders used in high-speed railway, the significant local dimension of the box girder causes the higher temperature and lower-speed of cooling inside the box girder and the larger temperature difference between the internal and surface of box girder. It will seriously reduce the box girders'quality and delay the project duration. To solve the problems, the temperature filed of hydration heat in the simply-supported box girder is simulated with the FEM software in this thesis and the result is compared with the data tested. The factors affecting the cooling effect of prestressed simply-supported box girder are discussed, and some new cooling measures are presented in this thesis. The main achievements are as follows:(1) Some cooling measures of the simply-supported box girders are presented based on the construction on-site and there are two box girders for high-speed railway are used for temperature test at the construction site of ShiWu Passenger Dedicated Lines. The results prove that the proposed cooling measures can speed up the construction progress and the turnover of templates, reduce the temperature difference between the internal and surface of box girder. So the cooling measures are economy and practicality.(2) With the FEM software, temperature filed of the simply-supported box girder using different cooling measures is simulated. In the process of simulation, seven load conditions are adopted for the simply-supported box girder, such as circulating water through prestressed ducts etc. The main factors of cooling measures are discussed and temperature filed of the simply-supported box girder using different cooling measures which are applied with different factors is simulated. The results show that:it is better to adopt two air blowers when the measure of ventilating through the box girder cavity is used, and the most appropriate temperature of cooling water is 30℃-20℃when the measure of circulating water through prestressed ducts is used. The simulation results and the measured data are corresponding. So the simulation proves applicable, and can be used to optimize the cooling measures of simply-supported box girder.(3) Some new cooling measures of simply-supported box girders are proposed in the thesis, and one of them is applied for national patent. The respective factors, applicability, construction methods, advantages and disadvantages are discussed.