基于ANSYS的T梁张拉阶段应力分析

发布时间：2018-07-13 13:32

【摘要】：简支T梁随着预应力钢筋的张拉,截面承受偏心压力,梁体自重逐步参与受力,随着张拉阶段的发展,T梁承受的预压应力逐渐增大,这时T梁与张拉台座之间将会慢慢分离,在张拉阶段预应力混凝土T梁的受力状态较复杂。张拉阶段T梁混凝土养护时间限制,其强度未完全达到其标准抗拉、抗压强度,在预应力钢筋的作用下可能会导致混凝土出现裂缝。预应力钢筋张拉阶段,T梁的受力可以视为简支状态,随着钢束张拉数量的增加,T梁所受的偏心预压力逐渐增大,梁体最终产生反拱。分析研究预应力钢筋张拉阶段T梁的应力变化以及反拱可以为以后类似工程的施工工程提供一定的借鉴。本文以宝贝河大桥的预应力预制T梁为研究对象,在主梁预制阶段,预埋钢弦式混凝土应变计,混凝土强度达到张拉强度要求时从T梁两端同时进行对称张拉,从而得到张拉阶段控制截面的应力,利用ANSYS软件建立T梁的实体有限元模型,模拟实际施工过程中预应力钢筋张拉产生的预压力,将有限元模型计算的数据与实测试验数进行对比以验证模型的准确性,进而对T梁在张拉阶段各控制截面处的应力变化及分布规律进行了分析,发现T梁顶板应力在支座附近为拉应力,随着距梁端距离的增大,拉应力值逐渐减小,最终过渡为压应力；分析T梁纵向应力沿T梁横截面的分布规律,认为T梁梁端存在剪力滞效应,跨中几乎不存在该效应；为分析不同张拉顺序对T梁的影响,分别比较了不同张拉顺序下T梁的应力、反拱、侧向位移的变化,结果表明不同张拉过程对T梁截面的应力变化及侧弯影响较大,但对最终反拱值影响不大；根据对锚固端的模拟,研究了局部承压混凝土的应力分布规律,结果表明锚下混凝土存在应力集中现象,此现象随着距锚固端距离的增大而逐渐消失,应力最终均匀的作用于截面上。
[Abstract]:With the tensioning of prestressed steel bar, the section of simply supported T beam is subjected to eccentric pressure, the weight of beam body gradually takes part in the force, and with the development of tensioning stage, the preloading stress of T beam increases gradually, and then the T-beam and the tensioning pedestal will be separated slowly. The stress state of prestressed concrete T-beam is more complicated in the tensioning stage. The strength of T-beam concrete in tensioning stage is not up to the standard tensile strength and compressive strength, which may lead to concrete cracks under the action of prestressed steel bar. The stress of T-beam in the tensioning stage of prestressed steel bar can be regarded as a simply supported state. With the increase of the number of steel strands, the eccentric preloading of T-beam increases gradually, and the beam body finally produces a reverse arch. The analysis and study of the stress change of T-beam in the tensioning stage of prestressed steel bar and the reverse arch can provide some reference for the construction of similar projects in the future. In this paper, prestressing prefabricated T-beam of Baohe Bridge is taken as the research object. In the prefabrication stage of the main beam, the steel string strain gauge is prefabricated, and the concrete strength reaches the tensile strength requirement, when the concrete strength reaches the requirement of tensile strength, the symmetrical tension is carried out simultaneously from the two ends of the T beam. The stress of the controlled section in tension stage is obtained, and the finite element model of T-beam is established by ANSYS software, and the pre-pressure produced by the tensioning of prestressed steel bar in actual construction is simulated. The data calculated by the finite element model are compared with the measured experimental data to verify the accuracy of the model, and the stress variation and distribution law of each control section of the T-beam in the tension stage are analyzed. It is found that the roof stress of T-beam is tensile stress near the support, and with the increase of the distance from the end of the beam, the value of tensile stress decreases gradually, and the ultimate transition is compressive stress, and the distribution of longitudinal stress of T-beam along the cross-section of T-beam is analyzed. It is considered that there is shear lag effect at the end of T-beam and almost no effect in the middle of span. In order to analyze the influence of different tensioning order on T-beam, the stress, reverse arch and lateral displacement of T-beam under different tensioning order are compared respectively. The results show that different tensioning processes have great influence on the stress change and lateral bending of T-beam section, but have little effect on the ultimate reverse arch value, according to the simulation of anchoring end, the stress distribution law of local confined concrete is studied. The results show that there is a stress concentration phenomenon in the concrete under anchor, which disappears gradually with the increase of the distance from the anchoring end, and the stress finally acts uniformly on the section.
【学位授予单位】：东北林业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U445.57

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