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Smart Structures and Systems
  Volume 9, Number 3, March 2012 , pages 207-230

Seismic and vibration tests for assessing the effectiveness of GFRP for retrofitting masonry structures
Paul Michelis, Costas Papadimitriou, Grigoris K. Karaiskos, Dimitra-Christina Papadioti and Clemente Fuggini

    Full-scale shake table seismic experiments and low-amplitude vibration tests on a masonry building are carried out to assess its seismic performance as well as study the effectiveness of a new multifunctional textile material for retrofitting masonry structures against earthquakes. The un-reinforced and the retrofitted with glass fiber reinforced polymer (GFRP) strips masonry building was subjected to a series of earthquake excitations of increasing magnitude in order to progressively induce various small, moderate and severe levels of damage to the masonry walls. The performance of the original and retrofitted building states is evaluated. Changes in the dynamic characteristics (lowest four modal frequencies and damping ratios) of the building are used to assess and quantify the damage states of the masonry walls. For this, the dynamic modal characteristics of the structure states after each earthquake event were estimated by performing low-amplitude impulse hammer and sine-sweep forced vibration tests. Comparisons between the modal results calculated using traditional accelerometers and those using Fiber Bragg Grating (FBG) sensors embedded in the reinforcing textile were carried on to investigate the reliability and accuracy of FBG sensors in tracking the dynamic behaviour of the building. The retrofitting actions restored the stiffness characteristics of the reinforced masonry structure to the levels of the original undamaged un-reinforced structure. The results show that despite a similar dynamic behavior identified, corresponding to reduction of the modal frequencies, the unreinforced masonry building was severely damaged, while the reinforced masonry building was able to withstand, without visual damage, the induced strong seismic excitations. The applied GFRP reinforcement architecture for one storey buildings was experimentally proven reliable for the most severe earthquake accelerations. It was easily placed in a short time and it is a cost effective solution (covering only 20% of the external wall surfaces) when compared to the cost for full wall coverage by GFRPs.
Key Words
    masonry structures; glass fiber reinforced polymers; shake table tests; structural identification; health monitoring; damage assessment
Paul Michelis : Institute of Mechanics of Material & Geostructures S.A., 22 Askiton str., Penteli, 152 36, Greece
Costas Papadimitriou, Grigoris K. Karaiskos and Dimitra-Christina Papadioti : University of Thessaly, Department of Mechanical Engineering, Volos 38334, Greece
Clemente Fuggini : D\'Appolonia S.p.A., Industrial Innovation Division, Via Martiri di Cefalonia, 2,
20097 San Donato Milanese (MI), Italy

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