【作者】 王力；

【导师】 刘素梅；

【作者基本信息】 武汉大学 ， 结构工程， 2019， 硕士

【摘要】 钢—聚丙烯混杂纤维混凝土(Hybrid Fiber Reinforced Concrete,HFRC)因其优良的基本力学性能而在土木工程中广泛应用。纤维—混凝土基体界面是纤维和基体两相材料相连接的纽带,也是传递应力的桥梁,纤维混凝土的力学性能与纤维—基体界面之间的粘结性能密切相关。为保证纤维与基体间形成良好的粘结作用,本文在国家自然科学基金“钢—聚丙烯混杂纤维混凝土多尺度本构关系:从纳米尺度到宏观尺度”(项目编号:51478367)的资助下,采用试验研究和离散元模拟相结合的方法,对钢—聚丙烯混杂纤维混凝土中纤维—基体界面粘结性能进行了系统研究,主要内容及成果如下:(1)通过纤维拉拔试验,直接测得了21组波纹型钢纤维与混杂纤维混凝土基体的粘结—滑移曲线,并以拉拔力、粘结强度和拉拔功作为粘结性能的参考指标,分析了钢纤维与混凝土基体间粘结性能随主要影响因素的变化规律,结果表明:钢纤维体积掺量为1.5%,聚丙烯纤维体积掺量为0.05%时,对混凝土的增强、增韧效果最佳;纤维埋深较小时,波纹型钢纤维在混杂纤维混凝土中的拉拔力将会随着纤维埋置深度的增加而提高,但纤维埋深大于8 mm时,粘结强度将随埋置深度的增加逐渐减小;基体强度对界面粘结性能有显著影响,当基体强度在C40～C50范围内,波纹型钢纤维与混杂纤维混凝土基体间的粘结性能随着基体强度的提高而提高。(2)通过PFC离散元软件,模拟了波纹型钢纤维从钢纤维混凝土中的拔出行为,对界面粘结性能的影响因素进行了补充分析,结果表明:平行粘结有效变形模量的增大使粘结力峰值减少,粘结力峰值提前出现,混凝土的脆性增加;粘结距离的增加,使钢纤维能与附近更多的基体颗粒产生粘结作用,从而使得钢纤维与混凝土基体间的粘结效果更好;摩擦系数主要影响粘结力—滑移曲线的形状和粘结力峰值,随着摩擦系数增大,颗粒之间的相互运动受到抑制,颗粒之间的摩擦力增大,粘结力增加,对抵抗混凝土开裂有利;钢纤维与基体的粘结效果与其形状相关:纤维直径越大,界面粘结力越大,但界面粘结强度越小;界面粘结力随波纹型钢纤维高跨比的增大而增大。(3)通过纤维拉拔试验和扫描电镜试验结果,研究了波纹型钢纤维与混杂纤维混凝土基体界面粘结机理,讨论各影响因素对界面粘结性能的作用,结果表明:钢纤维—混杂纤维混凝土基体界面间的化学粘结力随着纤维掺量的增大而先增大后减小;摩擦力随着纤维掺量的增大而增大;机械咬合力因纤维的掺入和基体强度的提高而提高。更多还原

【Abstract】 Steel-polypropylene hybrid fiber concrete(HFRC)is widely used in engineering due to its excellent basic mechanical properties.The fiber-concrete matrix interface is the connection link between fiber and matrix two-phase materials.The mechanical properties of fiber-concrete are closely related to the bonding properties between fiber-matrix interfaces.Given this,with the support of the Chinese National Natural Science Foundation(Grant No,51478367),the fiber-matrix interfacial properties in steel-polypropylene(PP)hybrid fiber reinforced concrete was studied by coupling of experimental investigation and discrete element simulation.The main work and results are summarized as follows:The main conclusions are as follows:(1)21 groups of steel-polypropylene hybrid fiber concrete pull-out specimens were designed to study the bonding performance of corrugated steel fiber-hybrid fiber concrete matrix by one-sided steel fiber pull-out tests.Taking peak pull-out force,bonding strength and pull-out work as the reference indexes of bonding performance,the change rule of bonding performance between steel fiber and concrete matrix with the major factors was analyzed.The peak pull-out force and pull-out work of corrugated steel fiber became the largest value when the steel fiber volume content was 1.5% and the polypropylene fiber volume content was 0.05 %.At the same time,the best reinforcement and toughening effect for concrete was obtained.When the embedded depth of steel fiber was small,the force of corrugated steel fiber pulled out from hybrid fiber concrete increased with the increase of the embedded depth of fiber,but when the embedded depth of fiber was greater than the optimal embedded depth(8mm),the bond strength would gradually decrease with the increase of the embedded depth.Matrix strength has a significant influence on the interfacial bond performance.The bond performance between corrugated steel fiber and hybrid fiber concrete matrix increased with the increase of matrix strength when the matrix strength is within the range of C40～C50.(2)The influence factors on the bonding performance of corrugated steel fiber-HFRC matrix were analyzed.The contact force of corrugated steel fiber was recorded through single steel fiber pull-out test and PFC discrete element numerical simulation,and the change rules of the bond between steel fiber and concrete matrix with the main influencing factors in the PFC model were analyzed:The increase of effective deformation modulus of parallel bond led to the decrease of the peak bonding force,and the peak bonding force would appear in advance.With the increase of bonding distance,the steel fiber could bond with more matrix particles nearby,so that the bonding effect between the steel fiber and the concrete matrix was better.The friction coefficient mainly affected the shape of the stick-slip curve and the peak bonding force.With the increase of the friction coefficient,the friction between particles increased and the bonding force increased.When the fiber diameter was thicker,the bonding force would be greater,but the bonding strength would be smaller.The interfacial bonding force increases with the increase of the aspect ratio of corrugated steel fiber.(3)The bonding mechanism of the fiber-matrix interface was also revealed by fiber pullout test and scanning electron microscope test.The chemical bonding force first increased and then decreased with the increase of fiber content.The friction increased with the increase of fiber content.The mechanical bite force increased with fiber incorporation and matrix strength increased.更多还原