Dynamic Wheel Loads of High-Speed Rail at Speeds Greater Than 400 km/h

The high-speed rail (HSR) line in South Korea has been in service since 2004 with a maximum design speed and operating speed of 350 km/h and 300 km/h, respectively. Recently, South Korea developed a high-speed electric multiple unit (HEMU-430X, 430-km/h eXperiment) with a maximum design speed and operating speed of 430 km/h and 400 km/h, respectively; the government was waiting for a trial run on a conventional HSR line. This study tried to predict wheel load fluctuation (WLF), one of the key factors affecting acceleration to speeds over 400 km/h. For WLFs to be understood accurately in the high-speed range greater than 400 km/h, field running tests were performed twice with the KTX-Sancheon trains on the Gyeongbu high-speed line. The trains traveled between Gwangmyeong and Daejeon at maximum running speeds of 302 and 335 km/h, respectively, and WLFs were measured with a telemetry system (radio data transmitter and receiver system) at varying speeds. On the basis of probabilistic data analysis with a Gaussian function, the WLF (sigma/P-st) normalized nondimensional parameter at speeds of 400 km/h and 500 km/h was modeled into quadratic functions. The WLFs at speeds of 400 km/h and 500 km/h were predicted to be 0.356 and 0.512, respectively. In addition, impacts from structures that greatly affected WLFs, such as turnouts, transition zones, and loose sleepers, were evaluated quantitatively. Of those, turnouts had the greatest impacts on the WLFs.