【作者】 胡铁明；

【导师】 黄承逵；

【作者基本信息】 大连理工大学 ， 结构工程， 2009， 博士

【摘要】 对已有损伤的混凝土简支梁桥采用简支变连续非预应力法实施加固,可有效提高结构体系的承载能力和正常使用性能。由于自重较大的原因,在我国钢筋混凝土公路桥梁设计规范中不考虑控制截面的疲劳验算。但对于后加固的连续梁体系,中支座截面仅承担二期恒载和活荷载所产生的负弯矩作用,且活荷载效应远大于二期恒载,中支座截面极易因疲劳而产生破坏。本文以辽宁省交通厅重点科研项目（200514）为研究背景,对简支变连续法加固的混凝土梁进行一系列疲劳试验研究:（1）通过倒置加载方式,对7根钢纤维自应力混凝土叠合梁进行负弯曲疲劳试验研究。建立了叠合层内钢筋的疲劳方程,提出了钢纤维自应力混凝土叠合梁的疲劳验算方法。试验结果表明,钢纤维自应力混凝土对叠合梁的裂缝宽度和刚度损失有较强的限制作用,疲劳循环达到200万次时,能够满足结构的耐久性能和正常使用性能要求。（2）分别以界面构造钢筋配筋率为0、0.082%和0.164%作参量,对负弯矩作用下的叠合梁进行疲劳性能试验研究。试验结果表明,构造钢筋可使钢纤维自应力混凝土叠合层与老混凝土梁协同工作,并可使钢纤维自应力混凝土充分发挥抗裂性能,从而降低结构面层裂缝的开展,提高结构负弯矩区的正常使用性能和耐久性能。（3）采用3种混凝土分别对已有损伤的简支梁进行加固,通过疲劳试验,研究不同种类混凝土加固的两跨连续梁疲劳性能。试验结果表明,用钢纤维自应力混凝土加固的连续梁,可使钢筋应力幅、中支座截面曲率及裂缝宽度等得到有效降低。与普通混凝土加固梁相比,经10万次疲劳循环,负弯矩区最大裂缝宽度约降低25.0%～32.0%。（4）以湿接缝接头界面的横向构造钢筋配筋率为参量,研究湿接缝接头界面的疲劳性能。试验结果表明,横向构造钢筋可提高湿接缝接头的疲劳抗剪和抗裂性能,并可间接提高中支座及跨中钢筋的疲劳抗弯性能,同时降低结构的整体刚度损失。建议工程中提高湿接缝接头界面的横向构造钢筋含量,其值不宜小于0.003bh₁。（5）对钢纤维自应力混凝土加固的两跨连续梁进行疲劳试验,通过与简支阶段无损伤的连续梁进行对比,分析简支变连续法加固的连续梁的疲劳性能。试验结果表明,简支阶段有损伤和无损伤的两种连续梁经1000次疲劳循环后,跨中和中支座钢筋应力幅、跨中截面刚度损失等方面均表现出了较好的一致性。中支座和跨中截面疲劳验算结果表明,用钢纤维自应力混凝土加固的连续梁,中支座截面抗弯刚度显著高于跨中截面,跨中截面内力可向中支座调整,从而提高结构体系的承载能力和抗疲劳性能。更多还原

【Abstract】 Damaged simply-supported beam bridges were strengthened by transforming the simply-supported beam bridges into continuous beam bridges under non-prestressed which could increase the beating capability and normal usage performance of the structure system effectively.As the deadweight was excessive large,the fatigue check was not considered in the design code of reinforced concrete highways and bridges in our country.But in the continuous beam system that was strengthened,as the mid-bearing section only bore the negative moment produced by the secondary dead loads and live loads and the efficiency of the live loads was greater bigger than that of the secondary dead loads,the middle support section was easy to be damaged due to fatigue.This article took the key scientific research project of Liaoning Province Department of Communications（200514） as the research background and carries out a series of fatigue test researches of the concrete bridges strengthened by transforming the simply-supported into continuous beams:（1） Researches in negative bending fatigue test were conducted for 7 steel fiber reinforced self-stressing concrete composite beams through inverted loading mode.Fatigue formula for reinforced steel bars in the composite layers was established and fatigue check method for steel fiber reinforced self-stressing concrete composite beams was proposed.The test results show that the steel fiber reinforced self-stressing concrete restricts greatly the crack width and rigidity loss of the composite beams and that when the fatigue cycle reaches 2 millions times,the structural durability and normal usage performance requirements will be satisfied.（2） Researches in fatigue performance tests of the composite beams under the negative moment were conducted respectively when the reinforcement ratios of an interface are 0, 0.082%and 0.164%.The test result shows that the structural steel bars are able to make steel fiber reinforced self-stressing concrete composite layer to work collaboratively with the old concrete beam and make the steel fiber reinforced self-stressing concrete give full play to its anti-crack performance,which could reduce consequently unfolding of crack on the structural surface and improve the normal usage performance and durability of the structural negative moment areas.（3） 3 kinds of concrete were used to strengthen the damaged simply-supported beams respectively.The fatigue performance of two continuous beams strengthened by different concretes was researched through the fatigue researches.The test results show that the continuous beams strengthened by the steel fiber reinforced self-stressing concrete can effectively reduce the reinforcement stress amplitude,middle support section curvature and crack width.Compared to the continuous beams strengthened by the common concrete,the max crack width in the negative moment areas after 100,000 fatigue cycles drops approx. 25.0%～32.0%.（4） With reinforcement ratio of structure reinforcement at junction of wet-joint as reference,research of the fatigue performance at junction of wet-joint was conducted.Test results show that the structural reinforcement is able to improve the fatigue shear resistance and cracking resistance performance at the junction of wet-joint,indirectly improve the fatigue bending resistance performance of middle supports and mid-span reinforcement and at the same time reduce the overall rigidity loss of the structure.It is advised that content of structural reinforcement at the junction of wet-joint should be increased and it shall be no less than 0.003bh₁.（5） Fatigue tests of double-span continuous beams which were strengthened by steel fiber reinforced self-stressing concrete were conducted.Compared with non-damage continuous beams in simply-supported stage,fatigue performance of continuous beams strengthened by transforming the simply-supported beams into continuous beams was analyzed.The test results show that after these two kinds of beams which were damaged and non-damage in simply-supported stage were applied 1,000 fatigue cycles,reinforcement stress amplitude and mid-span section rigidity loss of mid-span and middle support exhibit good consistency.Middle support and mid-span section fatigue check result shows that the middle support section flexural rigidity of the continuous beams strengthened by steel fiber reinforced self-stressing concrete is remarkably higher than that of the mid-span section and that the internal force of the mid-span section is adjusted to the middle support,which improve consequently the bearing capability of the structural system.更多还原