高强钢筋增强混凝土受弯构件刚度裂缝研究

发布时间：2019-06-20 14:30

【摘要】：高强钢筋的使用对于节约钢材,促进可持续发展有积极的意义,但是高强钢筋的应用也意味着正常使用状态下钢筋应力和应变的增加,构件裂缝宽度将增大,有可能由承载能力控制配筋设计变为由使用性能要求控制,这将限制钢筋强度的发挥,浪费钢材的良好性能。本文对HTRB600钢筋作为主要受力钢筋的高强混凝土受弯性能进行了研究,包括承载能力、裂缝、刚度等,为HTRB600钢筋在实际工程中的应用提供依据。本文通过对5根配HRB400钢筋和5根配HTRB600钢筋的高强混凝土受弯构件进行试验,详细观测记录了试验过程中裂缝的出现与开展、挠曲变形、破坏特征和极限承载力情况,进行对比分析。试验表明,HTRB600钢筋的强度设计值可取为500MPa,根据现行规范《混凝土结构设计规范》(GB50010-2010)的公式计算其极限承载能力,有足够的安全储备。试验中获得了大量的裂缝观测数据,结合以往关于400MPa级和500MPa级钢筋混凝土受弯构件的试验数据在规范的计算模式基础上,对计算公式进行分析,结果表明,对于钢筋应力较低的情况,规范推荐的短期最大宽度裂缝计算值与实测值比较吻合,但是在钢筋应力较高的情况下,规范公式对裂缝宽度的计算明显过于保守,因此建议在裂缝宽度计算中对钢筋正常使用情况下的应力设置限值。同样,根据试验中获得数据并结合以往的大量数据对规范短期刚度公式进行了分析,发现规范的刚度公式偏不安全,对其进行了修正。通过有限元软件ABAQUS进行数值分析,考察了钢筋强度等级对普通钢筋混凝土受弯构件截面延性的影响,以三个不同的指标进行对比。同时,考虑对强度较高的高延性钢筋如HTRB600钢筋施加一定的预应力,研究了有效预应力对构件受弯截面延性的影响。从能量的角度出发,分析钢筋强度等级对于构件耗能能力的影响,结合钢筋进入塑性阶段后的加载卸载准则,考察预应力对构件耗能性能的影响。从减小预制混凝土实心方桩运输和使用过程中开裂现象的需求出发,在混凝土预制方桩中使用HTRB600钢筋,对其施加一定的预应力。对两根预应力混凝土方桩进行了抗弯性能的试验,结果表明,预应力有效改善了其开裂性能,上述方法解决预制方桩易出现裂缝的问题效果明显。模拟设计了不同配筋情况的5个混凝土预制方桩,分析预应力张拉后的预应力损失,结果表明钢筋的预拉应力不宜过小,利用Fortran 90编制了计算机程序,以一些合理的基本假设为基础,考虑材料的非线性本构关系,用数值迭代的方法求解5根构件的开裂弯矩。利用Opensees对混凝土方桩进行耗能分析,研究钢筋强度等级对构件耗能能力的影响,结果表明高强钢筋的使用对桩的耗能性能的影响并不明显。
[Abstract]:The use of high strength steel bar is of positive significance for saving steel and promoting sustainable development, but the application of high strength steel bar also means that with the increase of stress and strain of steel bar in normal use, the crack width of component will increase, which may change from the design of bearing capacity control reinforcement to the control of performance requirements, which will limit the strength of steel bar and waste the good performance of steel. In this paper, the bending behavior of high strength concrete with HTRB600 steel bar as the main stress steel bar is studied, including bearing capacity, crack, stiffness and so on, which provides the basis for the application of HTRB600 steel bar in practical engineering. In this paper, five high strength concrete members with HRB400 steel bar and 5 high strength concrete members with HTRB600 steel bar are tested, and the occurrence and development of cracks, deflection, failure characteristics and ultimate bearing capacity during the test are observed and recorded in detail, and the comparative analysis is carried out. The test results show that the strength design value of HTRB600 steel bar is 500 MPA, and the ultimate bearing capacity is calculated according to the formula of the current code "Code for Design of concrete structures" (GB50010-2010), and there is enough safety reserve. A large number of crack observation data are obtained in the test. Combined with the previous test data of 400MPa grade and 500MPa grade reinforced concrete bending members, on the basis of the calculation model of the code, the calculation formula is analyzed. The results show that for the case of low steel bar stress, the calculated value of short-term maximum width crack recommended by the code is in good agreement with the measured value, but when the steel bar stress is high, The calculation of crack width by the code formula is obviously too conservative, so it is suggested that the stress limit value should be set in the calculation of crack width under the condition of normal use of steel bar. Similarly, according to the experimental data and combined with a large number of previous data, the short-term stiffness formula of the code is analyzed, and it is found that the stiffness formula of the code is not safe, and it is modified. Through the numerical analysis of finite element software ABAQUS, the influence of reinforcement strength grade on the section toughness of ordinary reinforced concrete members subjected to bending is investigated, and three different indexes are compared. At the same time, considering the application of certain prestress to the high ductile steel bar such as HTRB600 steel bar, the influence of effective prestress on the toughness of the bending section of the member is studied. From the point of view of energy, the influence of steel bar strength grade on the energy consumption capacity of members is analyzed, and the influence of prestress on the energy consumption performance of members is investigated in combination with the loading and unloading criterion of steel bar entering the plastic stage. In order to reduce the demand of cracking in the transportation and use of precast concrete solid square pile, HTRB600 steel bar is used in concrete precast square pile to apply certain prestress to it. The bending behavior of two prestressed concrete square piles is tested. The results show that prestress can effectively improve their cracking performance, and the above methods are effective in solving the problem that prefabricated square piles are prone to cracks. Five concrete precast square piles with different reinforcement conditions are simulated and designed, and the prestress loss after prestress tension is analyzed. the results show that the pretension stress of steel bar should not be too small. A computer program is compiled by using Fortran 90. Based on some reasonable basic assumptions, considering the nonlinear constitutive relation of materials, the cracking bending moment of five members is solved by numerical iteration method. The energy consumption of concrete square pile is analyzed by Opensees, and the influence of steel bar strength grade on the energy consumption capacity of members is studied. the results show that the effect of high strength steel bar on the energy consumption performance of pile is not obvious.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU375

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