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RC beam models damaged and strengthened with GFRP strips under bending loading and free vibration
Full text linkFour reinforced concrete (RC) beam models undamaged, damaged by notches and strengthened by external bonded (EB) glass fiber reinforced polymer (GFRP) strips have been experimentally studied. The paper aims to assess the availability of strengthening with EB GFRP strips in RC beams having a deep localized damage. The behavior of RC beams has been analysed under bending loading until failure. Furthermore, the assessment of RC beam models foresaw nondestructive control of damaged and strengthened models by free vibration tests to obtain frequency values at different damage degree. Damage, artificially obtained by notches with different width, on the midspan section and on the lateral location of beams, has been analysed. The envelope of frequency response functions (FRFs) obtained by dynamic tests was elaborated and changes of natural frequency values are then correlated to damage both to non-strengthened beam with notches and to strengthened beam models. Results of static tests on RC beams strengthened with filled mortar in the notched sections and EB GFRP strips have allowed to validate the strengthening of RC elements with composite material characterized by relatively low elastic modulus; further, it has been assessed maintenance of bond between concrete surface and GFRP strips until failure under bending loading
Experimental response of masonry walls in-plane loading strengthened with GFRP strips
Full text linkIn Italian seismic areas brickwork or stone masonry walls are commonly present in historic buildings. In recent years, the strengthening of masonry walls with external bonded (EB) fibre reinforced polymers (FRPs) has been increased to improve the tensile capacity of masonry that is normally weak. Many aspects of this strengthening method are not yet completely known; in particular, the debonding mechanisms of FRP strips need to be analysed through more investigation. The objectives have been, on one side, to investigate the behaviour of single-story shear brickwalls under in-plane loading with and without strengthening by Glass-FRP strips and, on the other hand, to analyze the mechanisms of debonding. Two experimental walls, built with historic solid clay bricks in scale 1/3rd, were subjected to precompression to simulate actual loading condition in masonry building for service loads and tested under cyclic shear force. One was strengthened after damage with EB GFRP strips - and then once again - subjected to the same loading until failure; another one was strengthened with GFRP strips without damage and subjected to the same path of loading until failure. The response of both models are presented and compared; finally, failure mechanisms are discussed
Historical masonry wallettes with plaster strengthened by CrFRM and GFRP
No full textKnowledge concerning the response of historic masonry to cyclic shear loading is fundamental for defining the behaviour of existing masonry buildings under seismic actions. Walls under cycle shear are known to be diagonally cracked due to low tensile strength of masonry. Many mechanical and geometric parameters influence the shear response of brickwork walls. One aspect too often underestimated is the presence of plaster on the external surface of walls. In this paper, experimental response and failure mechanisms of historic brickwork wallets, without plaster and with lime plaster reinforced by fibres, have been investigated under tensile tests by diagonal compression. The wallets have been strengthened with mortar reinforced by chrome fibres (CrFRM) and with glass fibre reinforced polymer (GFRP) net. The experiments were carried out previously on materials and triplets to define the strength of unreinforced masonry under compression and shear. Experimental results are shown obtaining shear criteria useful in practice
Experimental vibration response of homogeneous beam models damaged by notches and strengthened by CFRP lamina
No full textDetection of damage in RC beams strengthened with NSM CFRP rectangular rod by Finite Element Modeling
No full textAnalysis and modelling of RC elements strengthened with composite under vibration and static test - Keynote Lecture
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