足尺寸GFRP筋HFRC柱的轴压性能与理论研究

为了研究玻璃纤维增强聚合物( glass fiber reinforced polymer, GFRP )筋混杂纤维混凝土( hybrid fiber reinforced concrete,HFRC)柱的轴压性能,进行了5个GFRP筋HFRC柱和1个未配筋HFRC柱的轴压试验,分析了GFRP箍筋间距和纵筋配筋率对GFRP筋HFRC柱轴压性能的影响规律。结果表明：提高GFRP纵筋配筋率可以提高试件的承载力,箍筋间距小的试件的延性明显高于箍筋间距大的试件。根据试验数据回归出了GFRP筋HFRC柱峰值应力、峰值应变以及承载力的计算公式。     

冻融后钢纤维混凝土力学性能的试验研究

通过钢纤维混凝土冻融循环试验,分析了冻融循环次数、混凝土强度等级、钢纤维体积率等因素对钢纤维混凝土冻融后抗压强度、劈拉强度、抗折强度的影响,探讨了钢纤维对混凝土的增强机理.试验结果表明,钢纤维的加入对冻融循环后混凝土的抗压强度影响较小;当冻融循环次数较少时,钢纤维对劈拉强度和抗折强度的增加作用比较明显,而当冻融次数较大且钢纤维体积率较高(2%)时,钢纤维对混凝土的劈拉强度和抗折强度反而具有一定的负面影响;钢纤维混凝土强度等级的提高对改善钢纤维混凝土的抗冻性能较为有效.     

碳化环境下钢纤维混凝土基本性能试验研究

以混凝土强度等级、钢纤维体积率、碳化时间为变化参数,进行了碳化环境下混凝土、钢纤维混凝土和钢纤维高强混凝土试件的基本性能试验,测试了不同碳化时间混凝土和钢纤维混凝土的抗压强度、劈拉强度、抗折强度以及碳化深度,探讨了钢纤维对混凝土碳化性能的增强机理.研究结果表明:混凝土强度等级、碳化时间等对钢纤维混凝土的基本力学性能和碳化深度具有较为显著的影响,高强钢纤维混凝土具有较高的抗碳化能力;钢纤维体积率对钢纤维混凝土的抗碳化性能具有一定程度的影响.     

混杂纤维增强高性能混凝土拉压比试验研究

研究了揭示钢纤维和聚丙烯纤维混杂后对高性能混凝土强度和拉压比的影响.参照国家标准和试验方法,按不同的纤维掺量设计了9组混杂纤维增强高性能混凝土试件以及3组钢纤维增强高性能混凝土对比试件和1组普通高性能混凝土对比试件,进行了大量立方体抗压强度试验和劈裂抗拉强度试验研究,并对拉压比进行回归分析.结果在高性能混凝土中掺加适量的钢纤维和聚丙烯纤维后:对抗压强度影响不明显,但可使抗拉强度提高10%~30%,使拉压比增大到0.06~0.068;钢纤维体积掺量为0.8%、聚丙烯纤维体积掺量为0.11%时,混杂纤维增强高性能混凝土拉压比为0.068;混杂纤维增强高性能混凝土的劈裂抗拉试验为近似于延性断裂破坏.结论掺加适量钢纤维和聚丙烯纤维后,高性能混凝土的抗拉强度和拉压比均有不同程度的提高,这有利于提高高性能混凝土的抗裂性能和抗震性能.     

Charactersitics of Stress-strain Curve of High Strength Steel Fiber Reinforced Concrete under Uniaxial Tension

A whole of 110 specimens divided into 22 groups were tested with varying the volume fraction of steel fibers and the matrix strength of these specimens. The stress-strain behaviors of four types of steel fiber reinforced concrete （SFRC） under uniaxial tension were studied experimentally. When the matrix strength and the fiber content increase, the tensile stress and tensile strain vary differently according to the fiber type. The mechanisms of reinforcing effect for different types of fiber were analyzed and the stress-strain curves of the specimens were plotted. Some experimental factors for stress or strain of SFRC were given. A tensile toughness modulus Re0.5 was introduced to evaluate the toughness characters of SFRC under uniaxial tension. Moreover, the formula of the tensile stress-strain curve of SFRC was regressed. The theoretical curve and the experimental ones fit well, which can be used for references in construction.     

钢纤维混凝土准静态单轴受压力学性能

采用WAW-2000型微机控制电液伺服万能试验机对钢纤维体积率(Vf)为0%~3%、基体强度为C50的钢纤维混凝土(SFRC)进行了准静态三种应变率单轴压缩试验,测出了基体混凝土和SFRC应力-应变全曲线,试验结果表明:随Vf的增加,SFRC抗压强度仅有小幅度增长,韧性则增长幅度较大;随着应变率增大,SFRC强度提高,韧性呈现下降趋势,但Vf越大,韧性下降幅度越小;SFRC的弹性模量和泊松比均是不敏感的材料参数,随Vf的提高而分别微增与微减;还推荐了适合于SFRC应力-应变曲线的数学表达式。     

强碱溶液环境下混凝土力学性能试验研究

通过强碱溶液浸泡环境下普通混凝土和钢纤维混凝土的抗压、抗折强度试验,对比分析了耐碱剂的掺入对普通混凝土和钢纤维混凝土抗压强度、抗折强度、抗压强度腐蚀系数、抗折强度腐蚀系数的影响.结果表明,浸泡时间较短时,强碱溶液对普通混凝土和钢纤维混凝土均有一定的增强作用,但随着浸泡周期的延长,强碱溶液对普通混凝土和钢纤维混凝土均产生一定程度的腐蚀劣化;耐碱剂的加入可以提高普通混凝土和钢纤维混凝土抵抗强碱溶液腐蚀的能力,且掺加耐碱剂的钢纤维混凝土具有较强的抵抗强碱溶液腐蚀的能力.     

钢丝网混杂纤维增强水泥砂浆拉伸试验研究

对不同配合比的钢丝网钢-聚丙烯混杂纤维增强水泥砂浆进行拉伸试验,研究表明:体积分数为0.5%钢纤维与1.0%聚丙烯纤维混杂的钢丝网钢-聚丙烯混杂纤维增强水泥砂浆极限强度提高了15%,韧性也有大幅度的提升;比较可知该组配合比拉伸性能效果最佳.同时对拉伸试验过程进行了受力分析.     

Analysis of Dynamic Tensile Process of Fiber Reinforced Concrete by Acoustic Emission Technique

The fiber reinforced concrete has good dynamic mechanical properties. But corresponding research lacks the dynamic damage characteristics of the polypropylene fiber (fiber of low elastic modulus) and steel fiber (fiber of high elastic modulus) reinforced concrete under medium strain rate (10^-6 s^-1-10^-4 s^-1). In order to study the effect of strain rate on the damage characteristics of fiber reinforced concrete during the full curve damage process, the real time dynamic acoustic emission (AE) technique was applied to monitor the damage process of fiber reinforced concrete at three strain rates. The AE wavelet energy spectrum in ca8 frequency band and average AE peak frequency at three strain rates were analyzed. With the accumulation of damage, the AE wavelet energy spectrum in ca8 frequency band increased first and then decreased, and the average AE peak frequency increased gradually. With the increase of strain rate, the AE wavelet energy spectrum in ca8 frequency band and average AE peak frequency decreased gradually. The polypropylene fiber content has more obvious effect on the Dynamic increase factor (DIF) of the peak stress than the steel fiber content. The theoretical basis was provided for the monitoring of dynamic damage of fiber reinforced concrete based on the AE technique.     

混杂纤维增强高性能混凝土剪力墙性能研究

通过9片钢纤维-聚丙烯纤维混杂增强高性能混凝土剪力墙的水平低周反复荷载试验,分析了混杂纤维增强高性能混凝土剪力墙的破坏形态、抗剪强度、滞回特性、延性、耗能和刚度退化等问题。研究结果表明：掺加少量的钢纤维（0.3%）和聚丙烯纤维（0.11%）后,剪力墙的开裂荷载提高了30%左右,使高性能混凝土剪力墙的极限强度提高了40%以上;随着轴压比的增大,剪力墙的极限强度提高显著,但耗能和延性稍许降低。     

Complete splitting process of steel fiber reinforced concrete at intermediate strain rate

The complete splitting process of steel fiber reinforced concrete （SFRC） at intermediate strain rate was studied by experiment. The basic information of a self-developed SFRC dynamic test system matching with lnstron 1342 materials testing machine was given, and the experiment principle and the loading mode of cubic split specimen were introduced. During the experiment, 30 cubes of 150 mm×150 mm×150 mm and 36 cubes of 100 mm×100 mm×100 mm, designed and prepared according to C20 class SFRC with different volume fractions of steel fiber （0, 1%, 2%, 3%, 4%） were tested and analyzed. At the same time, the size effect of SFRC at intermediate strain rate was investigated. The experimental study indicates that SFRC size effect is not influenced by the loading speed or strain rate. When the steel fiber content increases from 0 to 4%, the splitting strength of SFRC increases from 100% to 261%, i.e. increasing by 161% compared with that of the common concrete. The loading rate increases from 1.33 kN/s to 80.00 kN/s, and the splitting tensile strength increases by 43.55%.     

混杂纤维对高性能混凝土拉压比的影响

为研究低掺量钢-聚丙烯混杂纤维对高性能混凝土拉压比的影响,采用正交试验法设计了18组混杂纤维高性能混凝土试件及1组普通高性能混凝土对比试件,通过标准试验方法进行立方体抗压强度和劈裂抗拉强度试验,试验中考虑的因素主要是钢纤维的特征参数(类型、体积率、长径比)和聚丙烯纤维体积率.分析各因素对高性能混凝土拉压比的影响,结果表明:混杂纤维高性能混凝土具有明显延性破坏特征,而普通高性能混凝土表现为脆性破坏,混杂纤维的掺入使高性能混凝土的拉压比最大提高了26.2%,平均提高了9.9%.在影响高性能混凝土拉压比的四个因素中,钢纤维类型的影响最大,其次是聚丙烯纤维的体积率,影响最小的是钢纤维长径比.高性能混凝土中掺入适量钢-聚丙烯混杂纤维后,拉压比显著提高,韧性得到明显改善.     

Experiment on mechanical properties of steel fiber reinforced concrete and application in deep underground engineering

Specimens of steel fiber reinforced concrete (SFRC) in volume ratios of 0%, 0.5%, 1% and 1.5% were prepared to study the supporting effect of SFRC at these different volume ratios in a deep soft rock tunnel. Experiments with mechanical properties of compressive strength in cubic specimens, cleave strength in cylindrical specimens and four-point flexure strength of sheet metal specimens were carried out. The experimental results indicate that SFRC in a volume ratio of 1% is superior in ranking to other volume ratios in terms of technique and economics. By means of a numerical simulation, given the characteristics of soft rock de-formation and damage at great depth, a new support substitution scheme of SFRC to replace plain concrete is proposed. The results of an industrial trial show that the support provided by SFRC can withstand large deformations of the surrounding rock. Good results have been obtained in a practical application.     

钢纤维对C60高性能混凝土弯曲韧性的影响

简要综述了国内外关于钢纤维混凝土弯曲韧性指数的计算方法,并选取我国现行的规程JGJ/T 221—2010试验方法,通过钢纤维高性能混凝土的弯曲韧性试验,研究了钢纤维体积分数和钢纤维类型对钢纤维高性能混凝土弯曲韧性的影响.结果表明:钢纤维高性能混凝土峰值荷载与弯曲韧性均随着体积分数的增大而提高;微细型钢纤维提高混凝土弯曲强度指标幅度最大,端钩型钢纤维提高混凝土弯曲韧性指标幅度最大.     

Effects of fibers on mechanical properties of high-performance concrete subjected to elevated temperatures

The compressive strength and ilexural toughness as well as fracture energy of fiber reinforced highperformance concrete （FRHPC） subjected to different high temperatures were studied. The results showed that after exposure at 300,600 and 900℃, the concrete mixes retained 88.1% , 41.3% and 10.2% of the original compressive strength on average, respectively. Steel fiber and polypropylene （PP） fiber were both effective in minimizing the damage effect of high temperatures on the compressive strength. The HPC reinforced with steel fibers showed higher flexural toughness and fracture energy before and after the high-temperature exposures. In comparison, PP fibers had minor beneficial effects on the flexural toughness and fracture energy. The mechanical properties of HPC reinforced with hybrid fibers （steel fiber ＋ PP fiber） were equivalent to or better than those of HPC reinforced with steel fibers alone. In addition, the failure pattern of FRHPC beams changed from pull-out of steel fibers at lower temperatures （20, 300 and 600℃） to tensile failure of steel fibers at higher temperature （900 ℃）.     

钢纤维混凝土三、四桩承台空间拉压杆模型的研究

根据24个试件试验和非线性有限元分析结果,探讨了钢纤维混凝土三、四桩厚承台的破坏模式和受力机理。结果表明:钢纤维混凝土三、四桩厚承台的传力模型符合拉压杆模型(空间桁架模型),并由此提出了基于拉压杆模型破坏的承载力计算公式。     

高温后钢骨再生混凝土柱的加固疲劳行为

针对大量建筑物在火灾中损坏急需修复,对高温（500º）后钢骨再生混凝土柱进行了纤维复合材料（CFRP）加固前后的静力轴压试验和加固后的疲劳实验,通过对破坏模式、承载力、荷载-位移曲线和荷载-应变曲线进行分析,结果表明：CFRP能有效提高高温后钢骨再生混凝土柱抗压强度,刚度和延性,承载力提高幅度最高可达141%;当再生混凝土取代率为50%时,CFRP加固短柱取得最大承载力;加固试件破坏形式为CFRP拉断、内部混凝土压碎以及钢骨上部屈曲,未加固试件的破坏形式为钢骨上部屈曲,外部混凝土剥落;加固后的钢骨再生混凝土柱305RF能够在上限为50%承载力的荷载下经过200W次疲劳试验,200W次后试件最大竖向位移接近相同试件静力破坏时对应位移。     

钢纤维对混凝土强度和韧性的影响

通过对234个钢纤维混凝土试件的力学性能试验,系统研究了钢纤维类型、体积分数、长径比和混凝土基体强度对钢纤维混凝土抗压强度、劈拉强度和弯曲韧性的影响.结果表明:钢纤维对混凝土抗压强度影响不大,但改变了受压破坏时的破坏形态;随钢纤维体积分数增大,混凝土劈拉强度和弯曲韧性显著提高,高强钢丝切断型钢纤维的改善效果最好,长径比越大,改善效果越明显.     

钢纤维混凝土抗冻性能试验研究

为了研究钢纤维混凝土的抗冻性能,采用快冻法进行了0%、0.5%、1.0%、1.5%、2.0%五种不同钢纤维掺量的混凝土在水中和3.5%氯化钠溶液中冻融试验。通过分析冻融循环次数和钢纤维体积率对钢纤维混凝土冻融后质量损失、劈裂强度损失和相对动弹性模量变化的影响,分析了冻融环境下钢纤维对混凝土的增强机理。并且用压汞法和SEM从微观上研究了钢纤维混凝土的孔径分布特征,讨论了微观结构对其抗冻性能的影响。研究表明,在冻融循环作用下掺入适量的钢纤维能够减小混凝土内部的孔隙率、增加密实度,有效阻止混凝土内部微裂缝的产生与发展,提高混凝土的抗冻性能。钢纤维掺量对混凝土抗冻性影响显著,掺量为1.5%时,钢纤维对混凝土抗冻性能改善效果最好。     

混杂纤维加固混凝土方柱的轴压性能试验研究

通过对不同加固方式下的钢筋混凝土短柱轴压性能试验,研究了混杂纤维约束混凝土柱的破坏形态及荷载与钢筋、混凝土之间的应变曲线关系,以承载力和延性为指标对比分析了不同混杂方式、混杂体积比的混杂纤维约束混凝土柱的受力性能.试验结果表明:混杂纤维的约束作用可以有效提高柱的承载能力,并使其延性得到显著改善;对于其混杂越均匀和二级拉伸破坏的试件,表现出更好的混杂效果,体现出混杂纤维的优越性.