Overloads on Japan's 130-mph Railroad Structures

Rapidly increasing traffic loads on the 130-mph New Tokaido Line of the Japanese National Railways was considered to affect life endurance of the closely designed structures supporting the line and endanger train operation in the future. In 4.5 yr since its opening to traffic on October 1, 1964, the average daily number of passengers has more than tripled from the initial figure of 60,539 while the average daily number of trains increased by about 2.7 times. Passengers much in excess of seating capacity had to be loaded while the original design load had been determined taking the weight of seated passengers only. The future trend of increases in weight and frequency of loadings and its effect were studied elaborately using statistical data and probability theories. It showed that 5% to 6% shortening of life expectancy is probable in certain short-span beams where the frequency and intensity of stresses are relatively high. Design load for future extension of the NTL was revised taking the aforementioned matter into account.