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细聚丙烯纤维混凝土介观离散力学模型及其Ⅰ型断裂强度负效应机理

MESOSCOPIC DISCRETE MECHANICAL MODEL FOR FINE POLYPROPYLENE FIBER REINFORCED CONCRETE AND FIBER DEGRADATION MECHANISM OF TYPE I FRACTURE
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摘要 细聚丙烯(PP,直径小于100μm)纤维混凝土Ⅰ型断裂强度随纤维含量增加呈现先增后减的变化规律,其机理尚不明晰。而且由于纤维数量过多,现有数值方法无法精细刻画细纤维混凝土力学行为。对此通过考虑细PP纤维亲水性提升基体局部水灰比的强度正效应和纤维桥接力强度贡献低于砂浆的强度负效应,并引入纤维直径等效系数(rf),实现介观尺度细聚丙烯纤维混凝土(PFRC)力学行为模拟。研究表明:纤维直径等效系数(rf)建议小于10;当纤维微量添加时,细PP纤维提升基体局部水灰比,使基体强度上升,此时正效应高于负效应;随着纤维含量增加,由于纤维桥接力贡献无法补偿相应面积基体强度,负效应持续增长,PFRC宏观Ⅰ型断裂强度下降。 The presence of fine polypropylene(PP)fiber with diameter≤100μm causes a fluctuation of the type I fracture strength in concrete.However,the mechanism of this phenomenon remains unknown,and the present mechanical models cannot describe the mechanical behavior of the fine PP fiber reinforced concrete(PFRC)due to the extremely expensive computational cost caused by the great number of fine fibers in matrix.To make up this gap,a mesoscopic discrete model is proposed by considering the improvement of water/cement ratio nearby PP fibers as the positive effect and the less mechanical contribution of fiber bridging force as the negative effect.The defining of the equivalent coefficient(rf)of fiber diameter makes it possible to simulate the mechanical behavior of PFRC.The numerical results show that the equivalent coefficient(rf)is recommended to be smaller than 10.The initial addition of PP fiber can increase the matrix strength,so that to slightly increase the PFRC type I fracture strength.The increase dosage of PP fiber causes the reduction of type I fracture strength due to the small strength contribution of fiber bridging force.
作者 沈雷 吴杰 邓通发 曹茂森 徐磊 李田雨 SHEN Lei;WU Jie;DENG Tong-fa;CAO Mao-sen;XU Lei;LI Tian-yu(College of Water Conservancy and Hydropower Engineering,Hohai University,Nanjing,Jiangsu 210024,China;Jiangxi Province Key Laboratory of Environmental Geotechnical Engineering and Hazards Control,Jiangxi University of Science and Technology,Ganzhou,Jiangxi 341000,China;Department of Engineering Mechanics,Hohai University,Nanjing,Jiangsu 210024,China;Anhui Provincial International Joint Research Center of Data Diagnosis and Smart Maintenance on Bridge Structures,Chuzhou University,Chuzhou 239099,China)
出处 《工程力学》 EI CSCD 北大核心 2024年第4期11-18,共8页 Engineering Mechanics
基金 江苏省科协青年科技人才托举工程项目(TJ-2023-043) 国家自然科学基金项目(51908195) 中央高校业务费项目(B220201030) 大学生创新训练项目(2022102941414)。
关键词 细聚丙烯纤维 混凝土 介观 离散模型 Ⅰ型断裂强度 fine polypropylene fiber concrete mesoscopic discrete model type I fracture strength
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