IMPACTⅣ is a measurement system to evaluate condition of bridge substructure by using natural frequency as an index. The value of natural frequency is calculated from the recorded response acceleration/velocity after hitting the top of the structure using the iron ball as illustrated in Figure 1. A vibration exciter is also used to apply the mechanically manipulated excitation to the structure, which make it possible to apply the system to retaining structure.


  • Easy to conduct
  • High repeatability
  • Quantitative evaluation
  • Possible to detect deformation of invisible location


Condition rating of bridge substructure and retaining structure


  • A mobile PC (with installation of IMPACT Ⅳ software)
  • Sensors (Wireless/Cabled/accelerometers are applicable)
  • Vibration exciter
  • Amplifier and wave generator


  1. Railway Technical Research Institute: Maintenance Standards for Railway structures (in Japanese), 2007.
  2. Nishimura, A., Okumura, F. and Tanamura, S.: Integrity Judg-ment of Railway Bridges by Percussion Tests for Structure Response, Quarterly Report of RTRI, Vol. 29, No.4, pp.184-189., 1988.
  3. Nakajima, S., Shinoda, M., Abe, K., Mai, T. and Ehara, T.: Study on inspection method for railway existing retaining walls using vibration testing, IS-Hokkaido 2012: 2nd international conference on transportation geotechnics, 2012.
  4. Shinoda, M., Nakajima, S., Abe, K., Tetsuo M. and Ehara, T.: Development of nondestructive inspection method of railway bridge substuructures with small vibration exciter, Proc of the International workshop on ICT in Geo-Engineering (ICTGE2012), 17-18 May 2012.