Quarterly Report (QR) was first published 43 years ago (in 1960) by the Railway Technical Research Institute (RTRI), an organization in the former Japanese National Railways (JNR), to release the results of its research and development to foreign countries, thereby aiming at contributing to the development of railway technologies in the world. When JNR was privatized and divided into JR companies in 1987, RTRI was reorganized as a foundation, since when it has continued publishing QR until today.
    RTRI is now promoting research and development in wide ranges from traditional technologies, such as those on high speed train operation and improvement of track maintainability to those of modern times, including psychology/physiology of passengers and train crew, the latest IT technology and application of bionics to railways. Thus, its activities encompass different railway fields as a whole across disciplinary boundaries expressed in a narrow sense. The results of its research and development are released from time to time at domestic as well as international meetings and on a number of journals, to attain reputation for high-quality performance and extensive activities.
    Each QR issue focuses on a special theme to transmit RTRI's research results summarized as theses to all over the world, with the author(s) of each thesis required to contribute to the publication with self-confidence and strain that the thesis is subject to the umpireship of the world, to well compensate for the slight non-rapidity of the publication. The theses in QR include those specifically written for the publication, English translation of the papers released in Japan, and rewritten versions of the theses issued overseas, which are all edited by the editorial staff with high quality and easiness to read as a motto. On behalf of the editorial committee members, the author wishes that QR be read by as many researchers and engineers as possible in worldwide railways, contribute to the technological development and improvement of safety and reliability, and provide opportunities of international exchange in research and development. To improve the quality of QR, candid opinions and requirements of readers sent to the editorial committee will highly be appreciated.
    This issue is a special edition on the fatigue strength and evaluation of the life of structures. Failure of rolling stock, track and electric structures and other structures that compose a railway system or their components in service will claim a number of people and property. Investigation and preventive measures against this phenomenon are an extremely important subject for researchers and engineers, in the sense that it emerged when the railway system made its debut, but has not been solved completely so far. Failure or cracking of structures and their members to become unusable is mostly caused by the fatigue due to repeated loads. To minimize the failure of this type, it is essential for those engaged in designing, manufacture, use and maintenance of railway vehicles and facilities to acquire the knowledge on this phenomenon. It is also desired by railway promoters to establish an appropriate technique to evaluate the life of structures and members in relation to fatigue, from the viewpoints of safety, reliability and economy.
    As indicated by its long history, the problem related to fatigue cannot be solved overnight. To reduce the failure due to fatigue, there are no other ways but to continue theoretical and experimental researches on fatigue ceaselessly and steadily based on the investigation of the phenomenon.