体外预应力加固连续梁桥极限强度研究

发布时间：2018-04-04 16:07

本文选题：体外预应力加固　切入点：连续梁桥　出处：《哈尔滨工业大学》2016年硕士论文

【摘要】：体外预应力加固技术因其具有施工方便、结构安全、造价经济等特点而广泛应用于旧桥加固之中,大量的桥梁结构在使用一定年限后出现结构老化、钢筋腐蚀、承载能力降低等问题,急需对结构进行加固维护,而体外预应力加固桥梁在承载能力极限状态下的性能是加固结构分析中的重要问题,现有的理论分析及试验研究大多是基于简支梁结构进行,对于连续梁桥的研究较少,基于简支梁的计算模型应用于连续梁桥时势必存在着一定的问题。因此,采用非线性有限元的方法对体外预应力加固结构极限状态进行分析不失为一种有效的手段,本文即利用商用有限元软件ANSYS建立体外预应力加固模型,完成对结构极限强度的研究。体外预应力的研究不同于体内有粘结预应力,体外束与混凝土之间仅在锚固点和转向装置处有连接,体外束与其附近的混凝土应变不相容,无法应用平截面假设,结构需要基于整体平衡条件进行分析。我国规范纳入了AASHTO-04规范的修正公式,公式通过破坏时形成塑性铰的数目关系推广到连续梁结构中,这种简化模式有其合理性,同时也存在一定的不足。本文首先对规范公式进行推导和分析,指出极限应力计算公式推导过程中的一些简化对计算结果的影响,分析公式应用于连续梁桥中存在的不合理之处。并通过简支梁与连续梁两个算例,得到不同公式之间计算结果的差异,确认本文分析脉络的明确性、合理性和针对性,并为接下来的内容做数据支持。接下来,通过有限元模型对不同跨数的连续梁桥、变截面连续梁桥及单一跨加固连续梁桥三种情况进行分析,分析得到以上工况对现行加固规范公式的适用性,并根据模型解与公式解的差异以及ANSYS模型中可见的破坏形式对公式提出修正建议。最后,本文设计了3个系列共27根体外预应力连续梁,利用提出的有限元软件对这些梁进行非线性全过程的分析,详细研究包括普通钢筋配筋率、有效预应力、转向块间距等参数对体外预应力筋的极限应力增量的影响,并与公式解进行比较,分析得到了三种参数对极限应力的影响程度超过公式所能体现的变化数值。研究的整个过程,系统的分析了极限应力计算公式对于连续梁桥的适用性,同时参数化分析了加固桥梁极限应力的影响因素,对体外预应力加固桥梁的工作性能和机理有了更加深刻的认识,分析结果可为体外预应力加固设计及关于极限应力公式的修正提供依据。
[Abstract]:The external prestressing reinforcement technology is widely used in the reinforcement of old bridges because of its characteristics of convenient construction, safe structure, economical cost and so on. A large number of bridge structures appear structural aging and steel bar corrosion after a certain number of years of use.It is urgent to strengthen and maintain the structure due to the reduction of the bearing capacity, and the performance of the bridge strengthened by external prestressing is an important problem in the analysis of the strengthened structure under the limit state of bearing capacity.Most of the existing theoretical analysis and experimental research are based on simply supported beam structure, but there are few researches on continuous beam bridge. There are certain problems when the calculation model based on simply supported beam is applied to continuous beam bridge.Therefore, using nonlinear finite element method to analyze the limit state of externally prestressed reinforced structure is an effective method. In this paper, the commercial finite element software ANSYS is used to establish the model of external prestressing reinforcement.Finish the study of the ultimate strength of the structure.The study of external prestress is different from that of internal bonded prestressing. There is only a connection between external beam and concrete at anchor point and steering device, and the external beam is incompatible with the strain of concrete nearby, so the assumption of plane section can not be applied.The structure needs to be analyzed on the basis of global equilibrium conditions.The revised formula of AASHTO-04 Code is included in the code of our country. The formula is extended to continuous beam structure by the number of plastic hinges formed during failure. This simplified model has its rationality, but also has some shortcomings.This paper first deduces and analyzes the formula of code, and points out the influence of some simplifications in the derivation of the formula of limit stress on the result of calculation. The analysis formula is applied to the unreasonableness of continuous girder bridge.Through two examples of simply supported beam and continuous beam, the difference of calculation results between different formulas is obtained, which confirms the clarity, rationality and pertinence of this analysis, and provides data support for the following contents.Then, through the finite element model, three kinds of cases of continuous beam bridge with different span number, continuous beam bridge with variable cross section and continuous beam bridge strengthened with single span are analyzed, and the applicability of the above working conditions to the current reinforcement code formula is analyzed.According to the difference between the model solution and the formula solution and the visible failure form in the ANSYS model, some suggestions for the correction of the formula are put forward.Finally, three series of 27 externally prestressed continuous beams are designed. The nonlinear whole process of these beams is analyzed by using the proposed finite element software. The detailed research includes the reinforcement ratio of ordinary steel bars and the effective prestressing force.The influence of steering block spacing and other parameters on the ultimate stress increment of external prestressed tendons is compared with the formula solution. The influence degree of the three parameters on the ultimate stress is more than the change value reflected by the formula.In the whole research process, the applicability of limit stress calculation formula to continuous beam bridge is systematically analyzed, and the influence factors of ultimate stress of strengthened bridge are analyzed parameterized.The working performance and mechanism of the bridge strengthened by external prestressing are deeply understood. The analysis results can provide the basis for the design of external prestressing reinforcement and the revision of the ultimate stress formula.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U445.72

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