General Manager

   Railway systems have come again to be appreciated in terms of pollution-minimum
characteristics, energetic efficiency, mass transportation capacity particularly
in urban area and so on. Futhermore, the active management of railway systems has
produced increase of their service level for customers, in particular after the
privatization and division of JNR. Speed-up technology, so far has been focused,
being accompanied with the development of several technologies like aerodynamics,
environment-friendly method, friction increase between wheel and rail and car
weight deduction.
   On the other hand, the maintenance of railway infrastructures, so to speak civil
engineering structures, should be naturally noted as one of the most important
factors to keep the train operation in stable condition, and as a matter of course
speed-up will often ask the execution of repair and reinforcement works after
examining car-structure interaction. It is not exaggerated to say that success or
failure of railway management may depend on the development in the maintenance
technology, considering large amout of existing structures. Maintenance of
structures is just on the new stage that will request more extensive international
collaboration.

Investigation and diagnosis procedures

   Railway Technical Research Institute in Japan has developed several
non-destructive investigation procedures for super/substructures of bridges.
   A bridge maintenance system for steel superstructure and an impacting procedure
for super/substructures and an impacting procedure mainly for substructures are
the representative effective maintenance procedures. That one give soundness level
and residual life span of structure, based on in-Situ measurement during train
passage and analysis of fatigue to repeated wheel load.
   This one gives soundness level on the basis of the analysis of response waves of
structures impacted by about 30kg weight, usually with natural frequency as an
significant index of their mechanical properties. Microtremor and passing train load
will be able be used instead of weight impact.
   The reinforced concrete maintenance system is also under development from the
chemical and mechanical viewpoints and there may exist many difficult steps to be
coped with in comparison with less complicated steel structures. Well, one of the
most important and difficult factors may be the applicable limit of the logic for
material characteristics of the structural members affected train load.
   These procedures are to be applied to the bridge structures affected and damaged
by Hyogo-ken-Nanbu Earthquake, Jan. 17, 1995.

Repair and reinforcement procedures

   Based on the diagnosis, some repair and reinforcement procedures will be followed
for super/substructures, Flange thickness increase, patch work to stop crack
extension, refinement of shoe, placement of stiffeners and so on have been adopted
for superstructures, and grouting of chemicals, bearing capacity increase, steel
plate encasing and so forth for substructures.
   Possibly, the more aged the structures will be, the more complicated and expensive
the reinforcement methods will be, and so, timely execution of reinforcement is
keenly expected in accordance with appropriate diagnosis. At the same time, the other
larger-scale reinforcement methods like change to composite structures, stressing by
outside cables and exchange of old members to new ones should be examined, depending
on time passage.
   Grouting and steel plate encasing will be principally applied to the structures
damaged by the aforementioned earthquake, and an earthquake-proof reinforcement
design is to be discussed for the existing railway civil engineering structures in
Japan.