Flexural Performance of Concrete-filled Composite Beams with Carbon Fiber-Reinforced Plastic Rebar Exposed to Standard Fires
국내 건설현장에서 장스팬 구조물이 증가함에 따라 콘크리트와 강재를 조합한 충전형합성보의 적용이 증가하고 있 다. 충전형합성보는 경제적이며 시공성이 향상되고 콘크리트 축열효과에 따라 내화성도 우수하다. 충전형합성보 내부에 휨성능 을 향상시키기 위해 Re-bar로 보강하여 사용한다. 이는 콘크리트 균열에 의해 부식 되어 내력저하를 유발한다. CFRP Re-bar는 경량이며 내부식성이 우수하다. 그러나 임계온도가 250℃로 낮기 때문에 화재에 취약으로 적절한 내화피복재를 적용해야된다. 따라서 열전달해석을 통해 내부 CFRP Re-bar가 보강된 충전형합성보의 온도분포를 확인하였다. 온도 상승에 따른 휨내력을 산 정하여 피복두께를 제안하고자 한다. 해석결과 단면크기에 상관없이 콘크리트 피복두께 40mm와 뿜칠내화피복재 20mm를 적용 하면 표준화재에서 3시간 내화성능을 확보하는 것으로 평가되었다.
As long-span structures increase in domestic construction sites, the application of infilled composite beams that combine concrete and steel is increasing. Infilled composite beams are economical, and their workability and fire resistance are excellent in accordance with the thermal storage effect of concrete. Such beams are used after reinforcing with rebars to improve the bending performance inside the infilled composite beam. However, they are also corroded by cracks in the concrete, which decreases yield strength. Carbon fiber-reinforced plastic (CFRP) rebar is lightweight, and has excellent corrosion resistance. However, given its critical temperature as low as 250 ℃, CFRP rebar is vulnerable to fire. Thus, appropriate fire-resistant insulations must be applied. In addition, the temperature distribution of the infilled composite beam reinforced with internal CFRP rebars was confirmed through heat transfer analysis. We propose the thermal insulation thickness by calculating the flexural strength in accordance with the increase of temperature. Based on analysis results, regardless of the cross-section size, 3-h fire-resistance performance was confirmed in the standard fire when the concrete insulation thickness of 40 mm and the sprayed fireproof coating material of 20 mm were applied.