Behavior of Steel Reinforced Concrete Buildings after Fire Damage

• Main Authors: Yuan-Chi Yang, 楊元吉
• Other Authors: 陳豪吉
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/32829629389713962470

博士 === 國立中興大學 === 土木工程學系所 === 105 === Concrete-Filled Box Columns (CFBCs) have been commonly utilized in Steel Reinforced Concrete (SRC) buildings, CFBCs filled with high-performance Self-Compacting Concrete (SCC) have already been a trend. There were many high-rise buildings not collapse after fire, and the structures were continue to use after evaluation. In order to fully understand SRC buildings are safe or not after fire damage, it is necessary to explore its behavior after fire damage, and provide the result as reference for reediting fire code in the future. To reach this goal, the research conducted 3 groups of tests to investigate. The first test is to examine fire resistance of CFBC after fire damage with full-scale (400mm × 400mm) specimens. The control group specimen was filled with SCC, experimental group specimens were filled with fiber SCC, and two of them were reinforced with deformed round bars and stirrups spacing were respectively 15 and 30 cm, thermal load was applied on the columns in form of CNS 12514 time-temperature curve in a gas furnace until the failure condition was reached. The test results showed that the fire resistance of fiber SCC was better than SCC, fire resistance time was 50% longer with reinforced deformed bars and stirrups, and fire resistance time was approximately 130% longer with shorter spacing of stirrups. The second test inspected residual-load-bearing capacity of CFBC filled with SCC after fire damage with full-scale specimens. The specimen of the control group was loaded at room temperature to measure the ultimate bearing capacity. On the other hand, fire tests were carried out on three specimens of the experimental group to investigate residual-load-bearing capacity after exposure to elevated temperatures (400℃, 600℃, and 800℃). The test results showed that the residual load-bearing capacity of CFBC specimen increased at 400℃ as compared with room-temperature axial force. The residual axial force of specimen at 600℃ was 4% lower than that at 400℃, however, was still higher as compared with that of the control group at room-temperature. With a further increase in temperature to 800℃, the residual-load-bearing capacity was substantially declined to near 84% as compared with that of the control group. With a view to providing a reference on evaluation of SRC buildings fire-resistance behavior, the third test was conducted to observe fire resistance capacity of RC beam and slab with non-full-scale specimens. The test results showed that the stiffness and residual-load-bearing capacity of RC beam specimen did not changed obviously with fire damage temperature under 600℃, nevertheless, the stiffness and residual-load-bearing capacity of RC beam specimen decreased obviously at 800℃. The ductility of RC slab specimen decreased gradually with the increased temperature of fire damage, and was prone to brittle fracture mode without warning. In particular, all RC slab specimens had none resistance of plastic deformation with a further increase in temperature to 800℃, the strength of specimen dropped suddenly as the ultimate load was reached. The results revealed：the mechanics behavior of column, beam and slab of SRC buildings would have been distinctly influenced when fire damage temperature were over 800℃. After fire damage, the SRC buildings were safe or not depended on exposing time to fire. However, it was confirmed that the fire resistance would be effectively enhanced with reinforced deformed bars and stirrups.