The use of fibre reinforced polymers (FRP) collaborating with other structural materials like concrete and masonry has rapidly grown both in newly designed structural elements and in the strengthening of existing ones. This thesis is in reference to the application of these anisotropic materials in civil engineering to restore the continuity of wooden connections, or as the reinforce of structural elements, beams and columns in C.A. The first part of the thesis refers to experimental tests on beams and columns in C.A. executed in the same laboratory of “Politecnico di Milano”. Regarding the first typology, for 8 full-scale specimens four point bending tests were executed were on beams reinforced through CFRP with different technical solutions. For the second experimental typology the examination as done through the execution of 12 full-scale specimens three points bending tests, to simulate two half-columns react (one superior and the other inferior of the floor deck), in this case the columns were reinforced with different CFRP binding configurations. Later on an analytical interpretation of the obtained results occurred. Thanks to these results it was possible to do a critical analysis on the new applied solution’s effectiveness, in order to define whether solutions will be used to reinforce and whether not, to avoid the possibility of weakening or driving to premature collapses of the structure. For timber structures, studies started almost two decades ago, with a lower impact initially and a faster growth now. For timber, the use of FRP products seems particularly promising for several reasons. An appropriate disposition of FRP’s offers the possibility of overcoming the directional limitations in the behavior of wood; timber is a light weight material and the addition of FRP’s does not increase weight significantly; reinforcement with FRP is less sensitive to environmental attack than more traditional metal reinforcement; the material is easily workable also on site, which makes it particularly appealing for interventions on existing structures. Referring to this second issue the work is based on experimental tests of Glued laminated timber with linear joints, also called “Glulam”, performed in the “Laboratorio Prove Materiali del Dipartimento di Ingegneria Strutturale del Politecnico di Milano”, and the analytical and numerical interpretation of the obtained results. The insert’s typology in FRP considered, are composed by carbon mats or glasses reinforced by carbon tapes; these new systems were compared with more old and traditional union method, realized using steel plates. Over 30 full-scale specimens realized were to observe the mechanical resistance of the different joints’ typology in FRP, predict the effectiveness of a structural connection. Furthermore, the interpretation of the numerical results through the Finite Element Method (FEM), in a linear field and not, allowed the integration of the experimental and analytical activity, retrieving the appropriate project and technological evaluation.
Il lavoro di tesi svolto riguarda l’applicazione dei materiali compositi (FRP) nell’ingegneria civile sia come materiale per il ripristino della continuità di elementi lignei, sia per il rinforzo di elementi strutturali, travi e colonne, in C.A.. La prima parte tratta di prove sperimentali su travi e colonne in C.A., anch’esse svolte nel medesimo laboratorio del Politecnico di Milano. Per quanto riguarda la prima tipologia sono state effettuate prove a flessione su quattro punti (four point bending) su campioni di travi rinforzate mediante CFRP con diverse soluzioni tecnologiche. Per la seconda tipologia sono state svolte prove a flessione su tre punti (three point bending) che simulassero il comportamento di due mezze-colonne (superiore ed inferiore all’impalcato del solaio), anche in questo caso rinforzate mediante diverse configurazioni di fasciatura in CFRP. Successivamente si è passati all’interpretazione analitica dei risultati ottenuti e mediante il loro confronto si è cercato di analizzare criticamente l’efficacia degli accorgimenti tecnologici impiegati, al fine di definire quali di questi possono essere adottati per il rinforzo e quali invece evitare al fine addirittura di non indebolire la struttura e portarla a precoci collassi. Per quanto riguarda la seconda parte, il lavoro si è concentrato su prove sperimentali di travi in legno lamellare con giunti lineari, svolte presso il Laboratorio Prove Materiali del Dipartimento di Ingegneria Strutturale del Politecnico di Milano, e sull'interpretazione analitica e numerica dei risultati ottenuti. Le tipologie di inserto in FRP considerate sono costituite da stuoie di carbonio o di vetro rinforzate con nastri di carbonio; questi nuovi sistemi sono stati confrontati anche con metodi di unione più tradizionali, realizzati con inserti in lamiera di acciaio. La campagna prove ha permesso quindi di osservare la resistenza meccanica delle varie tipologie di giunto in FRP, apprezzandone le buone potenzialità. Successivamente si è passati all'interpretazione numerica attraverso modelli ad elementi finiti (FEM), sia in campo lineare che in campo non lineare, che ha permesso di integrare l'attività sperimentale e analitica, ricavando opportune valutazioni progettuali e tecnologiche.
Materiali fibrorinforzati per il consolidamento di strutture in calcestruzzo armato e per la realizzazione di giunti in strutture lignee
OSTINELLI, ANDREA
2010/2011
Abstract
The use of fibre reinforced polymers (FRP) collaborating with other structural materials like concrete and masonry has rapidly grown both in newly designed structural elements and in the strengthening of existing ones. This thesis is in reference to the application of these anisotropic materials in civil engineering to restore the continuity of wooden connections, or as the reinforce of structural elements, beams and columns in C.A. The first part of the thesis refers to experimental tests on beams and columns in C.A. executed in the same laboratory of “Politecnico di Milano”. Regarding the first typology, for 8 full-scale specimens four point bending tests were executed were on beams reinforced through CFRP with different technical solutions. For the second experimental typology the examination as done through the execution of 12 full-scale specimens three points bending tests, to simulate two half-columns react (one superior and the other inferior of the floor deck), in this case the columns were reinforced with different CFRP binding configurations. Later on an analytical interpretation of the obtained results occurred. Thanks to these results it was possible to do a critical analysis on the new applied solution’s effectiveness, in order to define whether solutions will be used to reinforce and whether not, to avoid the possibility of weakening or driving to premature collapses of the structure. For timber structures, studies started almost two decades ago, with a lower impact initially and a faster growth now. For timber, the use of FRP products seems particularly promising for several reasons. An appropriate disposition of FRP’s offers the possibility of overcoming the directional limitations in the behavior of wood; timber is a light weight material and the addition of FRP’s does not increase weight significantly; reinforcement with FRP is less sensitive to environmental attack than more traditional metal reinforcement; the material is easily workable also on site, which makes it particularly appealing for interventions on existing structures. Referring to this second issue the work is based on experimental tests of Glued laminated timber with linear joints, also called “Glulam”, performed in the “Laboratorio Prove Materiali del Dipartimento di Ingegneria Strutturale del Politecnico di Milano”, and the analytical and numerical interpretation of the obtained results. The insert’s typology in FRP considered, are composed by carbon mats or glasses reinforced by carbon tapes; these new systems were compared with more old and traditional union method, realized using steel plates. Over 30 full-scale specimens realized were to observe the mechanical resistance of the different joints’ typology in FRP, predict the effectiveness of a structural connection. Furthermore, the interpretation of the numerical results through the Finite Element Method (FEM), in a linear field and not, allowed the integration of the experimental and analytical activity, retrieving the appropriate project and technological evaluation.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/21141