体外预应力简支钢梁自振频率研究
发布时间：2019-03-31 19:48
【摘要】：体外预应力技术是后张法预应力施工技术的重要组成,属于无粘结预应力的一种。对于体外预应力结构工程而言,结构自振特性关系到结构的健康安全。但体外预应力结构的自振特性研究是一个复杂的问题,现有研究主要集中在混凝土梁领域,且试验现象与理论分析之间尚存在一些分歧,不同理论之间关于预应力参数对结构自振频率的作用规律未能统一,而体外预应力钢梁自振频率研究更是鲜有涉及。为探究预应力参数对体外预应力钢梁自振频率的作用规律,正确识别结构动力特性,本文针对现有研究的不足之处,从钢结构中预应力系统作用机理的角度出发,依据预应力拉索的布索特点,分别探究直线型布索、直线耦合型布索及单折线型布索三种布索方式的预应力简支钢梁自振频率与预应力参数之间关系,运用结构动力学理论对上述三种体外预应力钢梁的自振频率进行理论研究,统一理论计算与已有试验结论;采用有限元软件ANSYS对理论分析结果进行验证;以现有典型试验模型为算例,探讨不同公式的计算结果。具体工作及成果如下:(1)对预应力系统的作用机理作简要阐述,基于作用机理建立直线型布索、直线耦合型布索及单折线型布索三种布索方式的预应力简支梁模型;采用能量法分析上述三种模型,列出振动方程,推导各布索方式下预应力简支钢梁自振频率计算公式。根据公式,预应力对预应力钢梁频率的作用规律与布索方式相关,即直线型布索预应力钢梁自振频率随预应力增大而减小,直线耦合型布索预应力钢梁自振频率随预应力增大而增大,单折线型布索预应力钢梁自振频率随预应力增大而减小;钢梁频率随偏心距及拉索截面积的增大而增大。(2)采用有限元分析软件ANSYS建立三种布索方式的预应力简支钢梁模型,分别研究体外预应力简支钢梁中预应力大小、偏心距及拉索截面对钢梁一阶频率的影响,验证理论计算结果。结果表明,本文频率计算公式得出的结果与有限元结果吻合,能够为工程应用提供一定参考。(3)介绍刚度修正法、非线性计算法及等效刚度法三种主要的钢梁频率计算方法,以有限元分析结果及典型频率试验结果为基准,分别得到包括本文方法在内的四种频率计算方法下钢梁一阶频率,并将理论值分别与有限元模拟值及试验值对比。结果表明:本文计算方法可以准确地描述预应力参数与钢梁频率之间关系,理论值与模拟值及试验值基本吻合。
[Abstract]:External prestressing is an important part of post-tensioned prestressed construction technology, which belongs to unbonded prestressing. For the external prestressed structure engineering, the natural vibration characteristic of the structure is related to the health and safety of the structure. However, the study of the natural vibration characteristics of externally prestressed structures is a complex problem. The existing researches are mainly focused on the field of concrete beams, and there are still some differences between the experimental phenomena and the theoretical analysis. The effects of prestressed parameters on the natural frequencies of structures are not uniform among different theories, while the study of the natural frequencies of external prestressed steel beams is rarely involved. In order to explore the effect of prestressing parameters on the natural frequency of external prestressed steel beams and correctly identify the dynamic characteristics of structures, this paper aims at the shortcomings of existing research and proceeds from the point of view of the action mechanism of prestressed system in steel structures. According to the characteristics of pre-stressed cables, the relationship between the natural frequency of prestressed simply-supported steel beams and the parameters of prestressing force is studied in three kinds of cable-laying methods, namely, linear cable distribution, straight-line coupling cable arrangement and single-fold cable placement, and the relationship between the natural vibration frequency and the prestress parameters is discussed. The natural vibration frequencies of the three kinds of external prestressed steel beams are studied theoretically by using the structural dynamics theory, and the theoretical calculation and the existing experimental conclusions are unified. The theoretical analysis results are verified by the finite element software ANSYS, and the calculation results of different formulas are discussed by taking the existing typical test models as an example. The concrete work and achievements are as follows: (1) the action mechanism of pre-stress system is briefly described. Based on the action mechanism, the prestressed simple-supported beam models of three kinds of cable-laying modes, namely, linear cable distribution, straight-line coupling cable distribution and single-fold cable distribution, are established. The energy method is used to analyze the above three models, the vibration equations are listed, and the formulas for calculating the natural frequencies of prestressed simply supported steel beams are derived under each cable arrangement. According to the formula, the effect of pre-stress on the frequency of prestressed steel beam is related to the arrangement of cables, that is, the natural vibration frequency of linear cable-laying prestressed steel beam decreases with the increase of prestress. The natural vibration frequency of straight-line cable-distributing prestressed steel beam increases with the increase of prestress, while the natural vibration frequency of single-fold cable-laying prestressed steel beam decreases with the increase of prestress. The frequency of steel beam increases with the increase of eccentricity and the sectional area of tension cable. (2) using the finite element analysis software ANSYS, three kinds of prestressed simply supported steel beam models are established to study the prestressing force in the external prestressed simply supported steel beam, respectively. The influence of eccentricity and cable section on the first-order frequency of steel beam is verified. The results show that the results obtained by the frequency calculation formula in this paper are in good agreement with those obtained by the finite element method and can provide some reference for engineering application. (3) the stiffness correction method is introduced. Based on the finite element analysis results and typical frequency test results, the first-order frequencies of steel beams under four frequency calculation methods, including the method in this paper, are obtained respectively by using the nonlinear calculation method and the equivalent stiffness method, which are based on the results of finite element analysis and typical frequency test. The theoretical value is compared with the finite element simulation value and the experimental value respectively. The results show that the relationship between the prestress parameters and the frequency of steel beams can be accurately described by the calculation method in this paper, and the theoretical values are in good agreement with the simulated values and the experimental values.
【学位授予单位】：江苏科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU391
本文编号：2451219
[Abstract]:External prestressing is an important part of post-tensioned prestressed construction technology, which belongs to unbonded prestressing. For the external prestressed structure engineering, the natural vibration characteristic of the structure is related to the health and safety of the structure. However, the study of the natural vibration characteristics of externally prestressed structures is a complex problem. The existing researches are mainly focused on the field of concrete beams, and there are still some differences between the experimental phenomena and the theoretical analysis. The effects of prestressed parameters on the natural frequencies of structures are not uniform among different theories, while the study of the natural frequencies of external prestressed steel beams is rarely involved. In order to explore the effect of prestressing parameters on the natural frequency of external prestressed steel beams and correctly identify the dynamic characteristics of structures, this paper aims at the shortcomings of existing research and proceeds from the point of view of the action mechanism of prestressed system in steel structures. According to the characteristics of pre-stressed cables, the relationship between the natural frequency of prestressed simply-supported steel beams and the parameters of prestressing force is studied in three kinds of cable-laying methods, namely, linear cable distribution, straight-line coupling cable arrangement and single-fold cable placement, and the relationship between the natural vibration frequency and the prestress parameters is discussed. The natural vibration frequencies of the three kinds of external prestressed steel beams are studied theoretically by using the structural dynamics theory, and the theoretical calculation and the existing experimental conclusions are unified. The theoretical analysis results are verified by the finite element software ANSYS, and the calculation results of different formulas are discussed by taking the existing typical test models as an example. The concrete work and achievements are as follows: (1) the action mechanism of pre-stress system is briefly described. Based on the action mechanism, the prestressed simple-supported beam models of three kinds of cable-laying modes, namely, linear cable distribution, straight-line coupling cable distribution and single-fold cable distribution, are established. The energy method is used to analyze the above three models, the vibration equations are listed, and the formulas for calculating the natural frequencies of prestressed simply supported steel beams are derived under each cable arrangement. According to the formula, the effect of pre-stress on the frequency of prestressed steel beam is related to the arrangement of cables, that is, the natural vibration frequency of linear cable-laying prestressed steel beam decreases with the increase of prestress. The natural vibration frequency of straight-line cable-distributing prestressed steel beam increases with the increase of prestress, while the natural vibration frequency of single-fold cable-laying prestressed steel beam decreases with the increase of prestress. The frequency of steel beam increases with the increase of eccentricity and the sectional area of tension cable. (2) using the finite element analysis software ANSYS, three kinds of prestressed simply supported steel beam models are established to study the prestressing force in the external prestressed simply supported steel beam, respectively. The influence of eccentricity and cable section on the first-order frequency of steel beam is verified. The results show that the results obtained by the frequency calculation formula in this paper are in good agreement with those obtained by the finite element method and can provide some reference for engineering application. (3) the stiffness correction method is introduced. Based on the finite element analysis results and typical frequency test results, the first-order frequencies of steel beams under four frequency calculation methods, including the method in this paper, are obtained respectively by using the nonlinear calculation method and the equivalent stiffness method, which are based on the results of finite element analysis and typical frequency test. The theoretical value is compared with the finite element simulation value and the experimental value respectively. The results show that the relationship between the prestress parameters and the frequency of steel beams can be accurately described by the calculation method in this paper, and the theoretical values are in good agreement with the simulated values and the experimental values.
【学位授予单位】：江苏科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU391
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