普通钢筋体外预应力加固RC梁数值模拟

发布时间：2018-06-07 18:05

本文选题：体外预应力加固 + 非线性　；参考：《郑州大学》2017年硕士论文

【摘要】：随着我国人均居住面积接近40平方米,新建建筑业将会逐渐萎缩,代之而来的将是维修加固改造行业。体外预应力加固作为简洁有效的一种加固方法,属于后张法无粘结的预应力结构体系。该加固方法具有消除应力滞后、加固材料自重小、对结构净空影响小等优点,因此得到了快速的发展。目前体外预应力筋多采用钢绞线,由于其屈服强度较高,加固梁破坏时,体外预应力筋还远未屈服,如果用普通钢筋代替钢绞线,合理地控制张拉量,使梁底纵筋和体外预应力筋在受力过程中能够同时屈服,就可以避免材料浪费,同时由于施工简便,对于工程的加固具有较大的实际意义。目前对体外张拉普通钢筋加固混凝土梁的研究较少,体内钢筋应力程度、体外张拉钢筋数量、张拉形式、预应力度等影响因素均需研究确定。本文从既有的实验出发,建立有限元模型,考虑体外的预应力筋与主体梁之间的变形不一致、材料的非线性等因素,选择合理的本构关系,利用生死单元模拟施加预应力之前的梁体实际承受的荷载,进行了如下研究:1)利用ANSYS软件对体外预应力加固简支梁的实验进行了全过程的模拟,对于是否考虑混凝土压碎、钢筋滑移的问题进行模拟,并与实验值比较,得到合理可行的模型;2)基于试验梁有限元模型的分析,提取该梁的跨中荷载-位移曲线、体外预应力筋的外荷载-应力变化曲线。考虑加固前梁的持荷水平、转向块的高度和个数、体外预应力筋在梁端的锚固高度、预应力度等因素,对加固梁体的屈服荷载和极限承载力进行了分析;3)将体外预应力筋由钢绞线替换成普通钢筋,根据加固前梁的持荷水平,计算梁底原有钢筋的应力水平。在保证梁底纵筋和体外预应力钢筋同时屈服的前提下,确定体外预应力钢筋的张拉应力大小,建立原有钢筋应力和体外预应力筋初始应力之间的关系式,探究体外预应力筋、体内梁底纵筋屈服时的外荷载的变化规律。研究表明,用有限元法模拟体外张拉预应力加固混凝土梁是可行的,用普通钢筋代替钢绞线,合理地控制张拉量,使梁底纵筋和体外预应力筋在受外力过程中能够同时屈服,这样就避免了材料浪费,对于实际加固工程具有一定的指导作用。
[Abstract]:As the per capita living area of our country is close to 40 square meters, the new construction industry will shrink gradually, which will be replaced by the maintenance and reinforcement industry. The external prestressing reinforcement, as a simple and effective reinforcement method, belongs to the post tensioned unbonded prestressed structure system. The reinforcement method has the effect of eliminating stress lag and strengthening the self weight of the material. At present, the external prestressing tendons are mostly used with steel strands. Because of their high yield strength, the external prestressing tendons are far from yielding when the reinforcement beam is destroyed. If the steel strand is replaced by a common steel bar, the tensile strength is reasonably controlled, so that the longitudinal and external tendons of the bottom of the beam are subjected to force. At the same time, the waste of materials can be avoided in the process. At the same time, because of the simple construction, it is of great practical significance for the reinforcement of the engineering. At present, there is little research on the reinforcement of concrete beams with ordinary steel bars in vitro. The factors such as the stress degree of the steel bar in the body, the number of tensile steel bars in the body, the form of tension, the pre stress and so on need to be studied. In this paper, we set up a finite element model from the existing experiments, consider the deformation inconsistency between the prestressing tendons and the main beams, the nonlinear factors of the material, select the reasonable constitutive relation, and use the life and death unit to simulate the actual bearing load of the beam before applying the prestress. The following study is carried out: 1) using the ANSYS software The whole process of the experiment of the simple supported beam strengthened with external prestress was simulated. The problem of whether the concrete crushed and the steel slips were taken into consideration was simulated, and the reasonable and feasible model was obtained by comparing with the experimental values. 2) based on the analysis of the test Liang Youxian element model, the load displacement curve of the beam and the external load of the external prestressed tendon were extracted. The load and stress variation curve. Considering the bearing level of the reinforced beam, the height and the number of the steering block, the anchorage height of the external prestressed tendon at the beam end, the pre stress and so on, the yield load and the ultimate bearing capacity of the reinforced beam are analyzed. 3) the external prestressed tendon is replaced by the steel strand as the ordinary steel bar, according to the loading of the reinforced front beam. The stress level of the original steel bar at the bottom of the beam is calculated. On the premise of guaranteeing the longitudinal reinforcement of the bottom of the beam and the external prestressed reinforcement, the tensile stress of the external prestressed reinforcement is determined, and the relationship between the original stress and the initial stress of the external prestressing tendon is established, and the external prestressed reinforcement and the yield of the longitudinal tendons of the bottom of the beam bottom are investigated. The study shows that it is feasible to use the finite element method to simulate the externally tensioned prestressed concrete beams. It is feasible to use the ordinary steel bar instead of the steel strands to reasonably control the tensile quantity, so that the longitudinal and external tendons of the beam bottom can be yielded simultaneously in the external force process, thus avoiding the waste of materials and strengthening the actual engineering. It has a certain guiding role.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU375.1

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