体外预应力梁的摩擦效应和二阶动力分析

发布时间：2018-01-13 07:37

本文关键词：体外预应力梁的摩擦效应和二阶动力分析　出处：《华侨大学》2017年硕士论文　论文类型：学位论文

【摘要】：体外预应力技术,作为后张预应力体系的重要部分,凭借施工简单、体外筋便于修理、替代等优点,在建筑以及桥梁领域得到快速发展,近年来更是在新建结构以及既有结构加固中得到广泛应用。目前,关于体外预应力结构的研究主要集中于简支梁以及静力性能方面,而对于连续梁和动力特性的研究相对偏少,尤其是关于体外筋与转向座之间的摩擦效应方面更有待深入研究。本文主要进行体外预应力梁摩擦效应以及二阶动力分析。回顾体外预应力增量的计算方法,并对各类计算方法的使用范围以及特点进行对比分析。引入简明的摩擦单元模拟转向座与体外筋间的摩擦效应,该单元位于转向座与相邻两段体外筋的角平分线上。进行各种因素下简支梁和连续梁的计算,包括不同的摩擦系数、体外筋面积、偏心距、荷载作用以及对称与反对称的加载模式。计算结果表明:偏心距对体外预应力增量影响明显;摩擦可降低梁的挠度和最大弯矩值,增加预应力增量;对于简支梁以及受对称荷载的连续梁,可以忽略弯矩、挠度的摩擦效应,但是对预应力增量的影响明显,对于受非对称荷载的连续梁,弯矩、挠度的摩擦效应不能忽略,对预应力增量的影响更为明显。本文分别采用等效刚度法、能量法以及集中质量法对体外预应力梁自振频率进行求解。在等效刚度法中,考虑体外筋对刚度的贡献,将体外预应力连续梁转化为具有更大刚度的受压梁。已有研究表明,无粘结与有粘结混凝土梁的预压力没有压缩软化效应,但是在体外预应力中预压力是否有压缩软化效应,未见相关文献研究。故在能量法中,本文着重研究体外预压力对梁二阶效应的影响,提出压缩软化效应的概念,得出预压力影响系数跟转向座数目有关。随着接触点数目的增加,偏心距损失减小,体外筋趋向于无粘结筋,预压力影响系数降低至趋于0,体外预压力几乎不产生压缩软化效应,几乎不影响梁的自振频率。在集中质量法中,在梁单元的弯曲刚度矩阵中引入预应力影响系数,考虑预压力对梁的影响。将三种方法的计算结果进行对比分析,得出考虑预压力影响下的能量法结果更为精确。
[Abstract]:External prestressing technology, as an important part of post-tensioned prestressing system, has been developed rapidly in the field of buildings and bridges by virtue of its simple construction, easy repair and replacement of external tendons. In recent years, it has been widely used in the construction and reinforcement of existing structures. At present, the research on externally prestressed structures is mainly focused on simply supported beams and static behavior. However, the study of continuous beam and dynamic characteristics is relatively less. Especially the friction effect between the external tendons and the steering seat needs to be further studied. The friction effect of the externally prestressed beam and the second-order dynamic analysis are mainly carried out in this paper. The calculation method of the external prestressing increment is reviewed. The application range and characteristics of various calculation methods are compared and analyzed. A concise friction element is introduced to simulate the friction effect between steering seat and external tendons. The element is located on the angular bisection line between steering seat and adjacent segments of external tendons. The calculation of simply supported beam and continuous beam under various factors, including different friction coefficient, external reinforcement area, eccentricity. The results show that the eccentricity has an obvious effect on the external prestressing increment. Friction can reduce the deflection and maximum bending moment of the beam and increase the prestress increment. For simply supported beams and continuous beams subjected to symmetric loads, the friction effects of bending moment and deflection can be ignored, but the effect on prestress increment is obvious, and for continuous beams subjected to asymmetric load, bending moment can be neglected. The friction effect of deflection can not be ignored, and the effect on prestress increment is more obvious. The equivalent stiffness method is adopted in this paper. In the equivalent stiffness method, the contribution of external tendons to stiffness is considered. The external prestressing continuous beam is transformed into a compression beam with greater stiffness. It has been shown that there is no compression softening effect in the pre-pressure of unbonded and bonded concrete beams. However, there is no literature study on whether pre-pressure has compression softening effect in external prestress, so in the energy method, this paper focuses on the effect of external pre-pressure on the second-order effect of beam. The concept of compression softening effect is put forward and the influence coefficient of pre-pressure is related to the number of steering seat. With the increase of the number of contact points the loss of eccentricity decreases and the external tendons tend to be unbonded tendons. When the influence coefficient of pre-pressure is reduced to 0, there is almost no compression softening effect and almost no effect on the natural vibration frequency of the beam in the concentrated mass method. The influence coefficient of prestress is introduced into the bending stiffness matrix of beam element, and the influence of pre-pressure on beam is considered. The results of the three methods are compared and analyzed. It is concluded that the energy method is more accurate considering the influence of prepressure.
【学位授予单位】：华侨大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O342

【相似文献】