Behaviours of novel prefabricated RAC-HSC composite beams subjected to fire: An experimental and numerical study

The combination of different types of concrete in prefabricated concrete structures may have promising potential in optimizing both structural mechanics and fire performance. Therefore, the fire-resistance tests of proposed Uand C-types recycled aggregate concrete (RAC) - high-strength concrete (HSC) composite concrete beams were carried out. Their thermal and structural behaviours were extensively analyzed and compared with those of monolithic beams. Subsequently, a sequential thermal-mechanical analysis model was developed. The test results revealed that the novel composite RAC-HSC beams exhibited lower mid-span deflection and less damage than the monolithic HSC beams under fire exposure. The internal temperatures of specimens with RAC were significantly lower than that of specimens without RAC. Based on the numerical analysis, the predicted fire resistance limits for the novel RAC-HSC composite beam were approximately 30 min longer than that for the monolithic HSC beam. The thickness of the RAC section in RAC-HSC composite beams was suggested by parametric studies. Generally, this study proved that the fire performance of the proposed novel RAC-HSC composite beams was better than that of HSC and RAC monolithic beams.