Study on Control of Crack Width in Reinforced Concrete Members under Sustained Loading

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In this study, experiments were performed on reinforce concrete beams under static loading and sustained loading, to investigate the influence of mechanical properties of concrete on flexural crack behavior. From the results of these experiments, use of high-strength concrete does not influence significantly on crack width under static loading, though it makes crack spacing larger. However, under sustained loading, it is efficient for control of crack width, because of low drying shrinkage and high tensile strength of high-strength concrete. To evaluate the influence of material properties such as drying shrinkage, creep of concrete and time effect of bond between reinforcements and concrete, finite element analysis was applied to the specimens under sustained loading. Analytical results showed that though volume change of concrete most influences on increase of crack width under sustained loading, bond characteristics near the crack surface have comparable effect.To improve the estimation of crack width, pull out test were carried out and cone-failure near the concrete surface was analyzed by finite element method. From the analytical results, bond degradation near the concrete surface was represented by tracing conic crack growth.To investigate the bond-slip relationship under sustained loading, bond tests using pull-out specimen were carried out. From the test results, the effects of deformed shape on reinforcement were evaluated and generalized bond-slip relationship were derived.