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RISS 인기검색어
- 검색키워드
- 저자 : Ditao Niu (검색결과 2 건)
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Structural Performance of Earthquake-damaged Beams in Fire
Bo Wen,Lu Zhang,Bo Wu,Ditao Niu 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.12
Post-Earthquake Fire (PEF) on frame structures usually leads to complicated and unpredictable thermal performance of damaged concrete members. In order to determine the structural performance of seismic-damaged Reinforced Concrete (RC) beams under PEF conditions, the RC frame structures are subjected to the shake table test. The test, used in conjunction with other existing seismic hazard data, demonstrates that the main geometric damage forms of RC beams after the earthquake are cracks and concrete spalling. Subsequently, calculating models of PEF RC beams are established in ABAQUS, and then the distribution of thermal field, hightemperature bearing capacity and reduction coefficient of seismic-damaged beams are proposed respectively. From experimental and numerical investigations, It can conclude that (a) the simplified numerical models are proven to accurately determine the fire performance of the damaged RC beams; (b) the thermal performance degradation caused by spalling is more severe than the degradation caused by cracking on PEF RC beams, which demonstrates that spalling takes a more important role than cracking; and (c) the prediction equation of the flexural bearing capacity reduction factor of PEF RC beams is feasible.
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Flexural Behavior and Prediction Model of Basalt Fiber/Polypropylene Fiber-Reinforced Concrete
Qiang Fu,Zhaorui Zhang,Wenrui Xu,Xu Zhao,Lu Zhang,Yan Wang,Ditao Niu 한국콘크리트학회 2022 International Journal of Concrete Structures and M Vol.16 No.5
The flexural behavior of basalt fiber (BF)/polypropylene fiber (PF)-reinforced concrete (BPRC) was investigated. When the content of BF and PF is 0.1%, the addition of fibers increases the compressive strength of concrete. A BF content of 0.1% has the most obvious effect on improving the compressive strength, but a hybrid fiber content of 0.2% exhibits a negative effect on the compressive strength. The addition of BF and PF can increase the flexural strength and the expansion tortuosity of the fracture cracks, thus enhancing the ductility of concrete. The hybrid fibers with content of 0.1% are most beneficial to increase the flexural strength. However, the ductility of concrete and the tortuosity of fracture crack decrease with the matrix strength, and the improvement proportion of fibers on the flexural strength also decreases. When the BF and PF are mixed, compared to the case of single fiber added, there is no significant change in the damage of BF, whereas the damage of PF is more severe. The flexural toughness index FTδ effectively characterizes the change in the flexural toughness of BPRC. The hybrid fiber contents of 0.1% and 0.2% exhibit the most significant improving effect on FT-l/600 and FT-l/150, respectively. Considering the influence of fibers on the compressive strength, flexural strength and flexural toughness of concrete, a hybrid content of 0.1% is the optimal choice of fiber content. A prediction model for flexural strength of BPRC is proposed based on the composite material theory.
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