【作者】 王永杰；

【导师】 宋彧；

【作者基本信息】 兰州理工大学 ， 结构工程， 2010， 硕士

【摘要】 在加固的同时,能够完成新旧结构协同工作问题是预应力加固技术的最大优势。体外预应力是后张预应力体系的一个重要分支,因其施工简便、节省材料、方便检修等诸多优点,近些年来发展迅速,已被广泛应用于建筑结构以及桥梁结构的加固领域。体外预应力筋与被加固构件之间可以相互滑动,两者的受力变形不协调,体外力筋受力后的应变与相应截面混凝土的应变并不相等,构件的承载力计算不适用于平截面假定。正常使用荷载下的体外预应力筋的应力增量计算问题,采用不同的分析方法与理论假定时,计算结果差异明显。索始用于桥梁结构,索在桥梁结构中的变形特点在于索的长度变形小,桥面结构的变形大,索的长度变形可以忽略不计。所以,现有索理论中就有“索长不变”的基本假定。在房屋结构中,体外预应力索结构的变形特点在于索长变形大,原有刚性结构的变形小,索长变形不能忽略。即原有索理论中“索长不变”的基本假定不能适用于体外预应力索结构的分析与计算。本文基于传统体外预应力加固技术,提出了斜腹杆索结构体外预应力加固技术；以简支梁的加固为研究对象,对加固后组合结构体系的参量做了基本假定,建立了索结构理论模型并进行了推导,得到了组合结构中索变形增量的计算式和索张力的计算式。在索结构计算中改变了索长不变的假定,分析了索变形、张力与荷载的关系,并对正常使用状态下体外预应力索的应力增量进行了简要分析。结果表明：索结构形状曲线为椭圆的一部分；索的最大水平张力位于跨中处,锚固点的水平力最小,该受力特点既能充分发挥索抗拉能力强的优势,又能减小索的水平分力对梁的不利影响；在沿索长的径向均布荷载作用下,索的长度增量与跨中挠度增量呈非线性关系,迭代计算时其精度与载荷步距大小有关,步距越小精度越高,反之则低。以普通弹簧模拟预应力索,按斜腹杆数量、载荷步距及垂跨比的不同对索施加斜向均布荷载,进行了7组试验,测试索的长度、最大垂度值和最大张力等特征值,研究了索的变形规律。试验结果表明,在其他条件不变的情况下：1)腹杆数越多,试验测试结果与理论分析结果越接近；2)迭代荷载步距越小,计算结果越准确；3)垂跨比越大,索的最大张力值越小。斜腹杆体外预应力索加固技术发挥了传统加固技术的长处,不仅可以加固水平构件,也可以加固竖向构件,应用范围更加广泛,实际工程应用更加简便。更多还原

【Abstract】 The best advantages of prestressed reinforcement technology are that the collaborative work between new and old structure start at the same time of the strengthening completion. The external prestress is one of the important branch of post-tensioned prestressing system,which is developed rapidly in recent years and being used widely in the fields of building and bridge structures because of the merits such as convenient construction, economizing material and convenient maintenance, etc.Because of the slippage and deformation inharmony between external prestress bar and reinforced member, the strain of external prestress bar after loading is not equal to the strain of corresponding concrete sections, and the carrying capacity calculation of structure member is not suitable for the plane surface assumption theory. There are significant diffenrences of calculation results using different analysis methord and various theory assumption about the calculation of external prestress bar stress increment under normal loading.The cable is applied to bridge structural system originally, a distinctive feature of cable is the smaller length deformation and the larger deck structure transform, which can be neglected as far as the deformation of cable length are concerned, and there is a theory of invariant cable length. The feature of external prestressed cable structure in building structure is the larger cable length deformation and the smaller transform of original structure and the length deformation can not be ignored. The invariant cable length basic assumption of original theory is not suitable for analysis and calculation of the external prestressed cable structure.A tilted belly poles cable structures external prestressed reinforcement technology is proposed on the basis of traditionally external prestressed reinforcement technology. The cable structures theoretical model is established and derived by taking the simply-supported beam reinforcement as the research object, the parameters of the reinforced composite structure system are basically assumed, the cable deformation increment and tension force formulas of the composite structure system are obtained. The paper modifies the unchanged cable length assumption in the calculation of the cable structures, which analyses the relations between deformation, tension force and the load, the results shows the cable structures figure is a part of the ellipse, the cable maximal horizontal tension force lies in the mid-span of the simply-supported beam, there is the minimal horizontal force in anchor point. Not only can such a stress characteristic fully develop the cable advantage of the high tensile capacity, but also it can decrease the unfavorable effects of cable horizontal force on the beam. Under the action of the radial uniform load, it shows the nonlinear relationship between the cable length incensement and deflection incensement. By means of iterative calculation,the precision is related to the magnitude of load-steps, the smaller load-steps, the higher precision, and the precision will be reduced on the contrary. The study of the paper provides theoretical references for the application of new technology.7 Unit Tests with ordinary spring were taken to simulate the prestressed cable. Vertical load was imposed on the cable, according to the variation of tilted belly pole members, load-steps and height span ratio. The deformation rule of the cable was studied by testing the characteristic values of cable, such as cable length, the maximum cable sag value, the maximum tension value.The results show that (other conditions are equal):(1) The larger the number of web member is, the more close the test result is to the theoretical analysis test;(2) The smaller height span ratio is, the more accurate the calculation results is;(3) The bigger height span is, the smaller the maximum tension value of cable is.The results can provide theoretical guide to the engineering.The tilted belly poles cable structures external prestressed reinforcement technology can be used in reinforcing horizontal members and the vertical elements, which would be applied more widely and easily in practical engineering.更多还原