部分预应力混凝土斜拉桥非线性性能与设计方法研究

发布时间：2018-08-03 19:21

【摘要】：中国是世界上斜拉桥数量最多的国家。本文从斜拉桥体系的受力特点出发,研究如何将部分预应力设计应用于混凝土斜拉桥上,使其在保证安全的前提下结构受力更为合理。本论文首先对部分预应力混凝土(PPC)结构的研究现状和将部分预应力技术应用于混凝土斜拉桥设计的理论进行了全面评述,然后考虑混凝土材料非线性,对PPC斜拉桥进行局部节段模型试验和全桥预应力设计参数分析,最后提出了适用于PPC斜拉桥设计的实用简化方法。论文主要工作有：(1)提出了混凝土斜拉桥主梁采用部分预应力混凝土的设计理念。按部分预应力设计的桥梁可以克服全预应力设计的不足,尤其适合于自重效应比重较小、活载效应比重较大、大部分区间压应力足够的斜拉桥；两者相结合,能有效减小斜拉桥主梁压应力和节约成本又不影响其正常使用要求和结构安全。(2)提出基于带刚臂的分层梁单元法,进行混凝土截面开裂和裂缝宏观发展过程的模拟,编写了相关计算程序。进一步通过对比不同轴压力作用下的钢筋混凝土梁和室内静载试验的预应力混凝土T梁数据,验证了程序的可靠性,克服了常规数值分析法在临近破坏时可能出现迭代不收敛的问题,简化了计算过程。(3)提出了混凝土斜拉桥两阶段设计的局部节段模型试验方法。为反映斜拉桥体系的受力特点,以实桥塑性最明显的区间作为试验区间,在模型两端设置无索区以消除边界条件的影响,加以弹性支撑以体现整体结构对局部节段模型的影响,进行节段模型设计。该方法包含了缩减阶段与缩尺阶段两部分,通过计算确定无索区长度和端部弹性支撑刚度的大小,保证了控制截面和控制索的受力与实桥的相近性,实现了在保证试验精度的前提下,用有限数量的索、梁组合模型来反映斜拉桥整体性能的试验目标。(4)开展了PPC斜拉桥室内节段模型试验。完成了试验梁设计和加工,确定了节段模型合理成桥状态,并在弹性范围内和不同裂缝宽度工况下进行重复控制加载以及结构破坏试验。试验发现裂纹在加载过程中有良好的平稳性和重复性且卸载后裂纹能完全闭合,主梁开裂后结构仍有较大承载空间,开裂后恢复的结构整体刚度有所下降但并不明显。完成了实测数据和理论计算结果对比,验证了理论计算的正确性。(5)进行了PPC斜拉桥内力重分布与参数分析。分析了混凝土斜拉桥开裂后跨中截面弯矩增量和挠度的非线性性能；对后期预应力数量和普通钢筋配筋率进行应力、裂缝宽度、裂缝开展和全桥承载能力的参数分析；分析了裂缝宽度和分布范围随荷载的增长趋势。计算表明主梁开裂后斜拉桥发生了明显的内力重分布,减小后期预应力能有效减小混凝土最大压应力,同时对加载后期的裂缝宽度影响较小,也不会降低全桥的承载能力。通过对三座不同跨径、不同边中跨比的混凝土斜拉桥的非线性对比分析,发现跨度越大开裂后的内力重分布程度越大,斜拉桥全桥承载力主要由斜拉索的强度控制。(6)提出了PPC斜拉桥主梁按裂缝宽度控制设计和简化的设计方法。根据主梁截面上、下缘的应力控制条件,提出用“应力平衡法”确定部分预应力混凝土斜拉桥主梁合理状态。讨论了多种裂缝宽度计算公式,提出了根据0.1mm裂缝宽度确定主梁允许拉应力的大小,从而作为部分预应力混凝土斜拉桥主梁设计参考。研究了部分预应力估算和布束方法,提出了部分预应力混凝土斜拉桥主梁设计步骤。进一步结合典型算例提出了按部分预应力进行PPC斜拉桥主梁简化设计和验算的方法。
[Abstract]:China is the country with the largest number of cable-stayed bridges in the world. This paper, starting from the stress characteristics of the cable-stayed bridge system, studies how to apply the partial prestress design to the concrete cable-stayed bridge to make it more reasonable under the premise of ensuring safety. First, the research status and the part of the part of the pre stress concrete (PPC) structure are studied in this paper. The theory of the application of partial prestress to the design of concrete cable-stayed bridge is reviewed. Then, considering the nonlinearity of concrete material, the local segment model test and the design parameter analysis of the PPC cable-stayed bridge are carried out. Finally, the simplified method suitable for the design of PPC cable-stayed bridge is put forward. The main work of this paper is (1) put forward the main work of this paper. The design concept of partial prestressed concrete is adopted in the main beam of concrete cable-stayed bridge. The bridge designed by partial prestress can overcome the shortage of full prestress design, especially suitable for a cable-stayed bridge with small gravity effect, large proportion of live load effect and enough stress in the interval. The combination of the two can effectively reduce the main of the cable-stayed bridge. The stress and cost saving of the beam do not affect its normal use requirements and structural safety. (2) a layered beam element method based on the rigid arm is proposed to simulate the macro development process of the crack and crack of the concrete section, and the related calculation program is written. The data of pre-stressed concrete T beams verify the reliability of the program, overcome the problem that the conventional numerical analysis method may appear iterative non convergence in the near failure, and simplify the calculation process. (3) the local segment model test method for the two stage design of the concrete cable-stayed bridge is proposed. The most obvious plastic interval is used as the test interval. The non cable zone is set at both ends of the model to eliminate the influence of the boundary conditions. The elastic support is made to reflect the influence of the whole structure on the local segment model. The segment model is designed. The method includes two parts of the reduction stage and the scale stage, and the length of the cable free zone and the end projectile are determined by calculation. The size of the rigid support stiffness ensures the similarity between the force of the control section and the control cable and the actual bridge. Under the premise of ensuring the accuracy of the test, the experimental target of reflecting the overall performance of the cable-stayed bridge is realized on the premise of guaranteeing the accuracy of the test. (4) the model test of the PPC cable-stayed bridge section is carried out. The design and processing of the test beam are completed. The reasonable bridge state of the segment model is determined, and the repeated control loading and structural failure test are carried out in the elastic range and the crack width. It is found that the crack has good stability and repeatability during the loading process and the crack can be completely closed after unloading. After the cracking of the main beam, the structure still has a larger bearing space and after the cracking. The overall stiffness of the reconstructed structure has been reduced, but it is not obvious. The correctness of the theoretical calculation is verified by comparing the measured data and theoretical calculation. (5) the internal force redistribution and parameter analysis of the PPC cable-stayed bridge are carried out. The nonlinear performance of the bending moment increment and deflection of the middle cross section of the concrete cable-stayed bridge is analyzed. Stress, crack width, crack development and full bridge bearing capacity are analyzed by the force quantity and the normal reinforcement ratio. The increase trend of the crack width and the distribution range with the load is analyzed. The calculation shows that the cable-stayed bridge has obvious internal force redistribution after the main beam cracking, and the post stress can reduce the maximum compressive stress of the concrete effectively. Force, at the same time, has little effect on the width of the cracks at the later stage of loading, and it will not reduce the bearing capacity of the full bridge. Through the nonlinear analysis of the concrete cable-stayed bridge with three different span and different side span ratio, it is found that the greater the degree of internal force redistribution after the larger span is cracked, the bearing capacity of the whole bridge of the cable-stayed bridge is mainly controlled by the strength of the cable. 6) the design method of the main beam of PPC cable-stayed bridge is designed and simplified according to the width of the crack. According to the stress control condition of the lower edge of the main beam, the rational state of the main beam of the partially prestressed concrete cable-stayed bridge is determined by the stress balance method. The calculation formulas of various crack width are discussed, and the determination of the width of the crack width is put forward according to the 0.1mm crack width. The main beam allows the size of tensile stress to be a reference for the design of the main beam of partially prestressed concrete cable-stayed bridge. The partial prestress estimation and beam distribution method are studied. The design steps of the main beam of the partially prestressed concrete cable-stayed bridge are put forward. The simplified design and test of the main beam of the PPC cable-stayed bridge according to the partial prestress are further combined with the typical example. The method of calculation.
【学位授予单位】：长沙理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：U448.27

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