IMPACTⅣ　

1．OUTLINE

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.

2．FEATURES

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

3．APPLICATION

Condition rating of bridge substructure and retaining structure

4．SYSTEM CONFIGURATION

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

Fig. 1 Use of IMPACT System in percussion test for condition rating of bridge sub structure

Fig.2 System configuration

Fig.3 Results of percussion test obtained from IMPACT system

Fig.4 Vibration exciter installed at top of bridge pier

Fig.5 Application of vibration exciter to existing retaining wall

Fig.6 Application of vibration exciter to existing retaining wall

REFERENCES

Railway Technical Research Institute: Maintenance Standards for Railway structures (in Japanese), 2007.
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.
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.
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.