Partner: Nikos Pnevmatikos

Technological Educational Institute Athens (GR)

Recent publications
1.Pnevmatikos N.G., Błachowski B., Hatzigeorgiou G.D., Świercz A., Wavelet analysis based damage localization in steel frames with bolted connections, SMART STRUCTURES AND SYSTEMS, ISSN: 1738-1584, DOI: 10.12989/sss.2016.18.6.1189, Vol.18, No.6, pp.1189-1202, 2016
Abstract:

This paper describes an application of wavelet analysis for damage detection of a steel frame structure with bolted connections. The wavelet coefficients of the acceleration response for the healthy and loosened connection structure were calculated at each measurement point. The difference of the wavelet coefficients of the response of the healthy and loosened connection structure is selected as an indicator of the damage. At each node of structure the norm of the difference of the wavelet coefficients matrix is then calculated. The point for which the norm has the higher value is a candidate for location of the damage. The above procedure was experimentally verified on a laboratory-scale 2-meter-long steel frame. The structure consists of 11 steel beams forming a four-bay frame, which is subjected to impact loads using a modal hammer. The accelerations are measured at 20 different locations on the frame, including joints and beam elements. Two states of the structure are considered: healthy and damaged one. The damage is introduced by means of loosening two out of three bolts at one of the frame connections. Calculating the norm of the difference of the wavelet coefficients matrix at each node the higher value was found to be at the same location where the bolts were loosened. The presented experiment showed the effectiveness of the wavelet approach to damage detection of frame structures assembled using bolted connections.

Keywords:

complex bolted lap connection, frame structure, wavelet analysis, damage detection

Affiliations:
Pnevmatikos N.G.-Technological Educational Institute Athens (GR)
Błachowski B.-IPPT PAN
Hatzigeorgiou G.D.-Hellenic Open University (GR)
Świercz A.-IPPT PAN

Conference papers
1.Błachowski B., Świercz A., Pnevmatikos N., Experimental verification of damage location techniques for frame structures assembled using bolted connections, COMPDYN 2015, 5th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering, 2015-05-25/05-27, Crete Island (GR), pp.C1511-1-12, 2015
Abstract:

This work is focused on experimental verification of existing techniques for localization of a loosened bolted connection. To this end, a laboratory-scale 2-meter-long steel frame is used. The structure consists of 11 steel beams forming a four-bay frame, which is subjected to impact loads using a modal hammer. The accelerations are measured at 20 different locations on the frame, including joints and beam elements. Two states of the structure are considered: a healthy and a damaged one. The damage is introduced by means of loosening two out of three bolts at one of the frame connections. Experimental modal analysis reveals that the loosened bolts in the connection cause a shift only in some of the frame’s natural frequencies, while the others remain insensitive to the damage.

Keywords:

bolted lap connection, frame structure, experimental modal analysis, damage location

Affiliations:
Błachowski B.-IPPT PAN
Świercz A.-IPPT PAN
Pnevmatikos N.-Technological Educational Institute Athens (GR)