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Modelação do comportamento de colunas de betão armado confinadas com mantas de GFRP: proposta de modelo de dimensionamento
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Authors
Abstract(s)
O confinamento de elementos estruturais de betão armado permite um aumento signi
ficativo da sua resistência e ductilidade, nomeadamente em colunas. Por conseguinte,
o nu´mero de trabalhos acerca do confinamento com recurso a novos materiais aumen
tou significativamente nas últimas décadas, entre os quais se destacam os pol´ımeros
refor¸cados com fibras (FRP). As propriedades apresentadas por esses materiais, nome
adamente os elevados mo´dulo de elasticidade, extensa˜o u´ltima, resistˆencia a` corros˜ao,
bem como o baixo peso pro´prio, a moldabilidade, a facilidade de aplica¸ca˜o e o baixo
custo, tornam os FRP materiais interessantes e competitivos para o refor¸co de colunas
por encamisamento. Consequentemente, encontram-se publicados diversos modelos de
confinamento capazes de prever o comportamento de colunas confinadas com FRP.
Atrav´es da an´alise de modelos de dimensionamento existentes, identificou-se que
estes foram na sua maioria calibrados para pol´ımeros refor¸cados com fibras de car
bono, sendo que na˜o existem modelos de dimensionamento aplic´aveis somente com
pol´ımeros refor¸cados com fibras de vidro (GFRP). Assim, desenvolveram-se propos
tas de modelos para colunas de sec¸ca˜o transversal circular e quadrada confinadas com
GFRP perante uma a¸ca˜o monot´onica. Para tal, calibraram-se, com base em resulta
dos experimentais dispon´ıveis na literatura, equa¸co˜es baseadas no modelo de quatro
paraˆmetros de Richard e Abbott (1975). Calibraram-se tamb´em os coeficientes ne
cessa´rios a` obten¸ca˜o da tens˜ao ma´xima de confinamento e da respectiva extens˜ao axial
com base no modelo de Mander et al. (1988) para a¸co˜es monot´onicas.
O modelo de dimensionamento proposto foi validado atrav´es da avalia¸ca˜o da cor
rela¸ca˜o com resultados de ensaios experimentais e por compara¸ca˜o com os resultados
de modelos propostos por outros autores. Concluiu-se que o novo modelo permite pre
ver de forma muito satisfato´ria a resposta de colunas circulares e quadradas confinadas
com mantas de fibra de vidro.
The confinement of reinforced concrete elements can significantly increase their strength and ductility, namely in columns. Therefore, the number of studies on confinement using new materials increased significantly, among which are fiber reinforced polymers (FRP). The properties as high elastic modulus and strain, low weight, high resistance to corrosion, easy to apply and low cost, turn the FRP sheet an interesting material for the external reinforcement of columns. Therefore, are published several confinement models able to predict the behavior of columns confined with FRP. However, through the analysis of confinement models, it is noticed that in the majority of the cases the models were calibrated for carbon fiber reinforced polymers (CFRP), and there are no applicable confinement models calibrated based only with glass fiber reinforced polymers (GFRP). Therefore, confinement models for columns with circular and square cross-section confined with GFRP under axial compression were developed. These models, based on the equations of the model by Richard and Abbott (1975), were calibrated using experimental results presented in the literature. The coefficients required for the computation of the maximum compressive stress and the corresponding strain, based on the model by Mander et al. (1988) for monotonic actions, were also calibrated. The new model was assessed by evaluation of the correlation with experimental test results and by comparison with the results of models proposed by other authors. The new model makes it possible to predict, very accurately, the response of both square and circular columns confined with GFRP sheets.
The confinement of reinforced concrete elements can significantly increase their strength and ductility, namely in columns. Therefore, the number of studies on confinement using new materials increased significantly, among which are fiber reinforced polymers (FRP). The properties as high elastic modulus and strain, low weight, high resistance to corrosion, easy to apply and low cost, turn the FRP sheet an interesting material for the external reinforcement of columns. Therefore, are published several confinement models able to predict the behavior of columns confined with FRP. However, through the analysis of confinement models, it is noticed that in the majority of the cases the models were calibrated for carbon fiber reinforced polymers (CFRP), and there are no applicable confinement models calibrated based only with glass fiber reinforced polymers (GFRP). Therefore, confinement models for columns with circular and square cross-section confined with GFRP under axial compression were developed. These models, based on the equations of the model by Richard and Abbott (1975), were calibrated using experimental results presented in the literature. The coefficients required for the computation of the maximum compressive stress and the corresponding strain, based on the model by Mander et al. (1988) for monotonic actions, were also calibrated. The new model was assessed by evaluation of the correlation with experimental test results and by comparison with the results of models proposed by other authors. The new model makes it possible to predict, very accurately, the response of both square and circular columns confined with GFRP sheets.
Description
Keywords
GFRP Confinamento de betão Colunas com secção circular Colunas com secção quadrada Modelos de dimensionamento GFRP sheets Confined concrete columns Circular and square cross-section Design-oriented model Engenharia Civil . Faculdade de Ciências Exatas e da Engenharia