【作者】 李跃；

【导师】 朱宏平；

【作者基本信息】 华中科技大学 ， 结构工程， 2011， 博士

【摘要】 斜拉桥主塔索塔锚固区是斜拉桥的关键部位,斜拉桥索塔锚固区受力性能的分析一直以来都是桥梁研究领域的热点。虽然近几年来,国内外针对斜拉桥索塔锚固区积累了不少的研究成果,这些研究成果对斜拉桥的设计、建造都具有一定的参考价值。但我们也注意到目前针对斜拉桥索塔锚固区的研究还存在一些不足和亟待解决的问题,例如：针对异形截面索塔的研究成果很少；计算机分析通常采用基于线弹性理论的有限元方法；未考虑收缩、徐变等混凝土的长期效应因素；索塔锚固区设计与优化方法的研究资料很少,等等。因此,探讨和揭示具有复杂形状截面的索塔锚固区的受力性能和优化设计方法就显得尤为必要,具有重要的实践指导意义。本文以马岭河特大桥为工程背景,以索塔锚固区足尺模型试验为基础,结合空间有限元仿真分析、STM(拉-压杆模型)分析方法以及数学规划法等结构力学与优化分析方法,对索塔截面形式采用非双轴对称六边形的这一类预应力混凝土异形截面索塔锚固区,展开相关问题研究。研究内容分为：索塔锚固区足尺模型试验研究、索塔锚固区整体分析研究、异形截面索塔锚固区优化设计研究和索塔锚固区日照温度场及应力分析研究四个部分,共6章。主要研究成果如下：(1)索塔锚固区足尺模型试验与有限元计算分析均表明：马岭河特大桥异形截面索塔的“连接部位外侧”以及“折线型长边内侧转角”两个区域是索塔结构的易裂区域,应注意加强该两区域的配筋构造；折线型长边的抗裂能力要低于直线型长边,折线型长边由于截面的局部削弱,使得外侧压应力分布发生变化,在中部受压显著；在混凝土未开裂前,测点荷载与应力保持较好的线性关系,实测应力值和有限元计算值基本吻合,说明所建有限元模型具有较好的准确性；索塔模型的抗裂安全系数不低于1.3,破坏安全系数不低于1.6,结构有足够的安全储备。(2)整体模型与节段模型的有限元对比分析表明：在设计索力作用下,整体模型与节段模型在相应节段位置的应力分布大体一致,说明节段模型的理论分析是正确的,节段模型的选取以及边界条件的处理是可行的；在预应力钢筋锚固端靠近长边外侧附近存在“预应力盲区”,在索力作用下,该区域形成较大的附加拉应力区,因此,建议将此区域的水平箍筋适当加密,以抵抗较大的附加拉应力,抑制裂缝的开展；在整体模型的基准节段上单独施加预应力及设计索力时,整体模型内产生的应力效应沿高度及厚度扩散衰减很快,模型短边的应力效应沿高度方向的衰减要明显显著于长边,说明短边的应力效应传递范围小,应力效应主要集中在索力加载面附近,因此,应尽量将U形预应力钢筋布置在斜拉索锚固点附近,以取得良好的受力效果。(3)拉-压杆模型分析方法(STM)是一种准确、可靠的斜拉桥索塔锚固区预应力设计与优化方法,STM分析结果依据索塔锚固区内部实际“力流”的分布,反映了索塔锚固区实际受力的需要,更符合结构受力合理性的要求；STM分析结果不仅优化了索塔锚固区预应力筋的用量,而且优化了预应力筋的平面布置,预应力筋在索塔截面短边处靠外侧布置,在长边处靠内侧布置更有利于受力；索塔截面形式对索塔锚固区的预应力配置和受力性能有较显著的影响,采用STM方法优化索塔截面后,预应力筋数量可以比原设计降低26.3%,而抗裂安全系数不低于1.6。(4)综合考虑外界气温及太阳辐射对混凝土索塔的影响时,可将太阳辐射的影响等效为索塔结构周围空气温度的升高,来建立马岭河特大桥索塔锚固区节段热分析的第三类边界条件；在得到索塔锚固区节段夏季和冬季太阳辐射条件下各方向塔壁的最不利温度场分布后,通过对日照温度场和斜拉索索力共同作用下的应力分析,得知无论是在夏季,还是在冬季,马岭河特大桥索塔锚固区节段在日照荷载与索力荷载共同作用下,索塔截面不会开裂。本文对马岭河特大桥预应力混凝土索塔锚固区的受力性能进行了相关研究,为索塔截面形式采用非双轴对称六边形的这一类预应力混凝土异形截面索塔锚固区的受力分析与优化设计提供了一定的参考,但受条件所限,本文在一些问题上,比如：基于STM方法的预应力混凝土索塔锚固区实用分析工具开发、综合考虑截面尺寸、预应力筋线形等多方面因素的综合优化分析、预应力混凝土索塔锚固区的非线性极限分析以及考虑徐变等长期作用影响分析等,还有待进一步深入研究。更多还原

【Abstract】 Anchorage zone is the key area of cable-stayed bridge pylon. The analysis of the mechanical performance of the anchorage zone is widely studied in the cable-stayed bridge, and the anchorage zone is the technological difficulty in the design and construction of cable-stayed bridge. Although many research of the anchorage zone of cable-stayed bridge pylon has been conducted in recent years, and those achievements provide valuable references for the design and construction of cable-stayed bridge, some problems still exist and need to be solved, such as:many researches focused on the pylons with rectangular section, whereas the researches regarding the abnormal shaped section are scarce; finite element analysis is usually based on the linear elastic theory and ignores the long-term effects of concrete; and the design and optimization methods for the anchorage zone of cable-stayed bridge pylon are very rare, etc. Therefore, studies on the mechanical performance and optimization method for the abnormal shaped anchorage zone of cable-stayed bridge pylon are necessary and significant in practical engineering.Based on the full-scale segment model test on the abnormal shaped anchorage zone of Maling River cable-stayed bridge pylon, the abnormal shaped anchorage zone of cable-stayed bridge pylon are studied by using finite element method (FEM), strut-and-tie method (STM) and mathematics programming method, etc. The studies are focused on four parts:full-scale segment model test on the abnormal shaped anchorage zone of Maling River cable-stayed bridge pylon, overall analysis of the anchorage zone of Maling River cable-stayed bridge pylon, optimization analysis of anchorage zone and thermal analysis of the anchorage zone of Maling River cable-stayed bridge pylon. These studies are concluded as:(1) The full-scale segment model test on the abnormal shaped anchorage zone of Maling River cable-stayed bridge pylon and its FEM analysis indicate that the outside of the joints between the polyline long side and short side, and the inside of polyline long side are the most dangerous zones, which require being strengthened. Cracking resistance of the polyline long side is weaker than that of the linear long side. The inside corner of linear long side cracks at load level 1.6 F0, whereas the inside corner of polyline long side cracks at load level 1.4 F0. Stress redistribution occurs in the outside of polyline long side. Before cracking, the stress was linear with load and its value was close to the theoretical one, which validate the finite element model. Cracking resistance coefficient of the full-scale segment model is no less than 1.3 and the destruction coefficient is no less than 1.6, which means the structure has an adequate safety capacity.(2) The comparison of the theoretical result of the segment model and the whole pylon model indicates that the stress distribution of the segment model and the whole pylon model is generally similar and the conclusions are the same, which mean the theoretical analysis of the segment model is correct, and the segment model and its boundary condition are viable in the FEM analysis. There exists prestress blind zone in the outside of the long side around the tendons anchorage zone, and great additional tensile stress occurs in the blind zone under the cable force. In consequence, the horizontal hoop reinforcement is suggested to be strengthened in the blind zone to withstand the great additional tensile stress. The decay of the stress effect of prestressed tendons and that of the cable force along the pylon in the whole pylon model are analyzed. The stress decay effect in short side is remarkable than the long side’s, which indicates that the stress effect transfers in a small area in the short side and concentrates in the cable anchorage. As a result, the hoop prestressed tendons should be disposed around the cable anchorage to achieve good stress capacity.(3) Strut-and-tie method (STM) is an accurate and reliable design and optimization method for the anchorage zone of cable-stayed bridge pylon. Based on the internal flows of forces in the anchorage zone, the STM analysis reflects the real stress field in the anchorage zone which accords with the actual need of a structure. The STM analysis not only saves the quantity of the prestressed tendons, but also optimizes the layout of the tendons. For example, the quantity is reduced by 21%, the tendons is preferable to lay near the outside of the short side and lay near the inside of the long side. The section shape of the anchorage remarkably influences the layout of the prestressed tendons and the mechanical performance of the pylon structure, optimal section obtained by STM not only reduces the tendons’ quantity by 26.3%, but also enhances the cracking resistance coefficient to 1.6. It means that the optimal pylon section could not only saves the prestressed tendons but also strengthens the cracking resistance.(4) Considering the influence of sun radiation, the sun radiation can be regarded as the rising of the air temperature, and thus the third kind boundary condition can be achieved to take thermal analysis of the anchorage zone. When the worst temperature distribution of the anchorage zone in summer or winter is obtained, the stress distribution of the anchorage zone under the temperature load and the cable load can be analyzed. Regardless in summer or in winter, the anchorage zone of Maling River cable-stayed bridge pylon will not crack.The paper focuses on the mechanical performance and the optimization design of the abnormal shaped anchorage zone of Maling River cable-stayed bridge pylon. It provides references for such abnormal shaped anchorage zone as nonaxisymmetrical sexangle section. Due to the limitation of testing conditions, in this paper, we study relevant problems based on Maling River cable-stayed bridge pylon, some problems such as the development of design tools based on STM, multi-factors optimization considering section shape, dimension and line shape of the tendons, nonlinear ultimate analysis of the anchorage zone and long term effect analysis considering creep, etc. deserves further research.更多还原