Abstract
This paper describes the results of long-term tests on reinforced concrete (RC) beams strengthened with hybrid composite beam (HCB) under two different sustained loads. Test specimens were fabricated to reflect the most common RC beam size used in school buildings in South Korea. The specimens had dimensions of 400 mm (width) × 600 mm (depth) × 6000 mm (length), and were tested with or without external strengthening by a hybrid composite beam (HCB). Test results showed that strengthening the RC beams with HCB not only reduced the instantaneous deflection but was also effective in decreasing long-term deflection. In this study, time-dependent factors were investigated using a modified version of the American Concrete Institute (ACI) equation. Time-dependent factors of HCB-strengthened RC beams found in the present work differed from those of other investigations due to various experimental conditions. In the present study, we found that the ACI equation may not provide a reasonable estimation of the long-term behavior of HCB-strengthened RC beams.
Highlights
Since seismic records were first collected in South Korea in 1978, two powerful earthquakes of5.1 and 5.8 magnitude were recorded in the country, without significant human injuries or serious damage to building structures in the past three years
It was found that the long-term deflections of hybrid composite beam (HCB)-strengthened reinforced concrete (RC) beams after 1 year were approximately 245% and 176% higher than those of the instantaneous deflection at 33% and 50%
The long-term deflections of HCB-strengthened RC beams at the two different sustained loading levels of 33% and 50% at 1, 3, 6 and 12 months were, on average, 27%, 22%, 25% and 26% lower than those of unstrengthened RC beams, respectively
Summary
Since seismic records were first collected in South Korea in 1978, two powerful earthquakes of. Test results showed that time-dependent deflection, strain and curvature increased with the increase in the applied moment in the beams, and the rate of increase in strains and deflections was higher in the initial period of loading and tended to reduce with time under sustained loading In this investigation, the age-adjusted elastic modulus method appears to be realistic in predicting the long-term behavior of concrete beams reinforced with CFRP. Sobuz et al [12] reported on the deflection and cracking behavior of RC beams externally reinforced with CFRP laminates from different degrees of strengthening schemes and two types of sustained loads up to 180 days. We knew that the majority of previous long-term tests on RC beams with FRP strengthening were conducted with relatively small or scaled-down member size [14,15,16]. The used RC beams of 6000 mm in length and 400mm × 600 mm in cross section represented the typical size used in school buildings in South Korea
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