【作者】 罗建；

【导师】 秦士洪；

【作者基本信息】 重庆大学 ， 土木工程， 2021， 硕士

【摘要】 预应力技术在混凝土结构工程中应用十分广泛,除常规的预应力结构以外,工程中还出现了各种预应力衍生结构,如在梁的局部区域布置和张拉预应力筋、通过在梁端水平加腋将预应力筋锚固在梁端相交梁上、用体外预应力技术加固结构的局部区域等,这些特殊预应力结构的受力响应较常规预应力结构复杂,且无相关规范供结构设计人员参考。为了深入了解这些结构的力学性能,需要针对性的精细化分析。本文基于有限元理论,建立了考虑材料和几何非线性的预应力梁统一分析模型,并与三个既有试验梁进行对比,验证了所建模型的合理性。利用统一建模方法构建了多种特殊的预应力结构,系统的研究了不同参数对局部预应力、体外预应力和水平加腋预应力混凝土梁受弯性能的影响。论文的主要的研究工作和成果如下:(1)利用微分方程等推导了等效荷载计算公式,验证了等效荷载法在预应力筋较大曲率情况下的可靠性;基于经典荷载等效法和力法对局部预应力梁进行了理论分析,推导出几种常见的超静定局部预应力梁的次内力计算公式,并用有限元程序验证了传统等效荷载法对局部预应力梁的适用性。(2)建立了预应力梁的统一分析模型,并验证了模型的可靠性。通过选择合适的材料本构模型,合理的构建无粘结预应力筋与混凝土之间的连接作用(主要为刚性弹簧布置),合理的定义各部件之间的接触关系等来保证模型的准确性;利用已有的预应力梁试验数据,与分析结果相互对比,验证了所建有限元模型的合理性。(3)针对多种布筋方式的局部预应力梁,设计并建立了5个系列的有限元模型梁,利用有限元程序对这些模型梁完成了非线性全过程分析。详细研究了非预应力筋和预应力筋面积、预应力筋长度等主要参数对局部预应力梁受弯性能的影响。(4)针对水平加腋预应力梁,设计并建立了2个系列的有限元模型梁,分别模拟两种预应力筋锚固情况:1)预应力筋锚固在梁端相交梁上,并设置水平加腋构造;2)预应力筋锚固在预应力梁身侧面上,并设置水平加腋构造。研究分析了水平加腋区内预应力筋线型、负弯矩区非预应力筋面积对预应力混凝土超静定梁受弯性能的影响。本文的研究成果可为预应力结构设计人员提供参考,有助于特殊预应力结构的合理、正确使用。更多还原

【Abstract】 Prestressing technology is widely used in concrete structure engineering.In addition to the conventional prestressed structure,there are also various prestressed derived structures.For example,prestressed tendons are tensioned at important parts of the beam,The prestressed reinforcement is anchored on the intersecting beam by adding the horizontal axils at the beam end.Local reinforcement of damaged parts with external prestressing technology,etc.The mechanical properties of these special prestressed structures are much more complex than those of conventional prestressed structures.And there is no specification for structural designers to refer to,In order to understand the mechanical properties of these structures,detailed analysis is needed.Based on the finite element theory,a unified analysis model of prestressed beams considering material and geometric nonlinearity is established in this paper.The rationality of the model is verified by co MParing with three existing experiments.Unified modeling method is used to construct a variety of special prestressed structures.A systematic study the effects of different parameters on local prestressed beams,external prestressed beams and horizontal axillary prestressed concrete beams on flexural performance.Main research contents:1 The equivalent load calculation formula is derived from the differential equation,which verifies the reliability of the load balance method under the condition of large curvature of prestressed tendons.Based on the classical load balance method and the force method,the theoretical analysis of the locally prestressed beams is carried out,and the formulas for calculating the secondary internal forces of several common locally prestressed structures are calculated.The applicability of the classical load balance method to the locally prestressed beams is verified by the finite element program.(2)By selecting the appropriate material constitutive model,the connection between the unbonded prestressed tendon and concrete is reasonably constructed(mainly the arrangement of the rigid spring),and the contact relationship between the components is reasonably defined to ensure the accuracy of the model.The rationality of the finite element model is verified by co MParing the existing test data of prestressed structure with the analysis results.(3)For local prestressed beams with a variety of reinforcing methods,five series of finite element model beams were designed and built,and the nonlinear analysis of these model beams was completed by using the finite element program.The influences of the main parameters such as the area and length of the non-prestressed tendons on the mechanical performance of the locally prestressed structures are studied in detail.(4)For prestressed beams with horizontal axils,two series of finite element model beams were designed and established to simulate the anchorage of two prestressed reinforcement respectively:1)The prestressed reinforcement is anchored on the intersecting beam at the beam end,and the horizontal axillary structure is arranged;2)The prestressed tendon is anchored on the side of the prestressed beam body,and the horizontal axillary structure is arranged.The influences of prestressed bars’ linear shape in the horizontal axillary zone and non-prestressed bars’ area in the negative bending moment zone on the flexural performance of prestressed concrete statically indeterminate beams are studied and analyzed.The research results of this paper can provide reference for the designers of prestressed structures,and help the rational and correct use of special prestressed structures.更多还原