环境和荷载共同作用下钢筋混凝土桥梁疲劳性能研究
发布时间：2018-09-07 20:07
【摘要】：疲劳作为结构脆性破坏的重要诱因已在工程领域引起重视,随着交通流量和密度的攀升,混凝土桥梁的疲劳问题也逐渐显现,环境侵蚀因素的影响进一步加剧了桥梁结构的疲劳劣化。因此,开展环境和荷载共同作用下钢筋混凝土桥梁疲劳性能研究具有积极的现实意义。本研究在对实际桥梁疲劳荷载和应力状态进行研究计算的基础上,有针对性地开展了设计荷载和调查荷载两种应力水平下钢筋混凝土梁的疲劳试验;进一步考虑环境因素影响,进行了设计荷载应力水平下的锈蚀钢筋混凝土梁疲劳试验;对比分析了应力水平和环境因素对混凝土梁疲劳极限循环次数和应变演变的影响规律;提出了环境和荷载共同作用下的钢筋混凝土梁截面疲劳应力理论计算方法,并运用Matlab软件编制了计算程序。方法中考虑了疲劳和环境因素作用引起的混凝土和钢筋材料的损伤;通过条带法体现了构件层面的疲劳应力计算方法与材料层面的区别,并反映了钢筋与混凝土共同工作以及钢筋混凝土受弯构件中应变的分布特征;通过锈蚀钢筋与混凝土之间的应变协调关系考虑了钢筋与混凝土之间粘结性能退化的影响;引入疲劳和锈蚀引起的损伤对混凝土对本构关系、钢筋有效受力面积的影响,通过粘结单元的粘结力-滑移曲线考虑锈蚀引起的粘结力的退化,在ANSYS软件平台上实现了环境和荷载共同作用下钢筋混凝土梁疲劳性能的有限元模拟,进一步揭示了应力水平和锈蚀两种因素对钢筋混凝土梁疲劳性能的影响规律;最后,在总结已有试验和理论研究成果的基础上,对环境和荷载共同作用下的钢筋混凝土桥梁疲劳寿命进行了初步评估。本研究形成的主要结论如下:通过中小跨径钢筋混凝土桥梁的疲劳应力验算,实际桥梁在现行公路桥梁设计规范设计荷载应力水平下满足规范要求,在实际调查荷载作用下已不满足规范要求;普通钢筋混凝土梁构件层面的疲劳损伤机理与材料层面的机理存在差别,钢筋混凝土受弯构件的疲劳损伤可以分为两个阶段,疲劳寿命的前期(约占整个寿命的10%)主要受压区混凝土的疲劳损伤控制,而疲劳引起的纵向钢筋的损伤(表现为钢筋有效受力面积的减小)主导并控制着构件的整个疲劳过程;应力水平的提高加速了构件的疲劳损伤和劣化,应力水平提高后,疲劳寿命大幅下降,但疲劳破坏前构件的劣化程度相当。当应力幅由设计荷载提高20%至调查荷载应力水平时,试验梁极限循环次数下降了31.2%~44.6%,疲劳破坏前构件中钢筋应力的增长率由12.08%上升至12.3%;当应力幅提高70%时,试验梁纵向钢筋的应力增幅提高至15.5%,极限循环次数下降超过66%;锈蚀也大幅降低了梁的疲劳寿命,并加剧了梁体的劣化,但锈蚀对疲劳的影响起始于疲劳初始状态,不同锈蚀率下构件的损伤速率相同。在试验采用相同的设计荷载应力水平下,锈蚀率约5%的钢筋混凝土梁疲劳寿命较未锈蚀梁下降34.9%以上,疲劳破坏前其纵向钢筋和混凝土应变增长率与同应力水平下未锈蚀梁相当;通过汇总本研究和同类试验研究结果,得出设计荷载应力水平下的未锈蚀梁和纵筋锈蚀率5%的锈蚀梁不存在疲劳破坏的风险,调查荷载应力水平下的未锈蚀梁运营后期存在发生疲劳破坏的风险;如同时两种因素的影响,我国混凝土设计规范中给定的应力幅限值在实际荷载作用和锈蚀条件下已不能满足实际桥梁的要求。
[Abstract]:Fatigue, as an important inducement of brittle failure of structures, has attracted much attention in the engineering field. With the increase of traffic flow and density, fatigue problems of concrete bridges gradually appear. The fatigue deterioration of bridge structures is further aggravated by the influence of environmental erosion factors. Based on the research and calculation of fatigue load and stress state of actual bridge, the fatigue test of reinforced concrete beams under design load and investigation load is carried out, and the design load stress water is carried out considering the influence of environmental factors. The fatigue test of corroded reinforced concrete beams under flat condition is carried out. The influence of stress level and environmental factors on the fatigue limit cycles and strain evolution of concrete beams is compared and analyzed. In this method, the damage of concrete and steel bar caused by fatigue and environmental factors is considered, the difference between the fatigue stress calculation method and material layer is reflected by strip method, and the joint work of steel bar and concrete and the distribution characteristics of strain in reinforced concrete flexural members are reflected. The strain compatibility relationship between concrete and reinforcement takes into account the deterioration of bond strength between reinforcement and concrete; the influence of damage caused by fatigue and corrosion on the constitutive relationship of concrete and the effective bearing area of reinforcement is introduced; the degradation of bond strength caused by corrosion is considered by the bond force-slip curve of bond element, and the degradation of bond strength caused by corrosion is considered in ANSYS software platform. The finite element simulation of the fatigue behavior of reinforced concrete beams under the combined action of environment and load is realized, and the influence law of stress level and corrosion on the fatigue behavior of reinforced concrete beams is further revealed. Finally, on the basis of summarizing the existing experimental and theoretical research results, the reinforced concrete beams under the combined action of environment and load are mixed. The main conclusions of this study are as follows: through the fatigue stress checking calculation of small and medium span reinforced concrete bridges, the actual bridge meets the requirements of the code under the design load stress level of the current highway bridge design code, and under the actual investigation load, it does not meet the requirements of the code; The fatigue damage mechanism of reinforced concrete beams is different from that of materials. The fatigue damage of reinforced concrete flexural members can be divided into two stages. The early stage of fatigue life (about 10% of the total life) is mainly controlled by the fatigue damage of concrete in the compressive zone, while the longitudinal damage of steel caused by fatigue (represented by steel). The increase of stress level accelerates the fatigue damage and deterioration of the components. After the increase of stress level, the fatigue life decreases greatly, but the deterioration degree of the components before the fatigue failure is comparable. When the stress amplitude increases from 20% of the design load to the stress level of the investigated load, The ultimate cycling times of the test beams decreased by 31.2%~44.6%, and the increase rate of steel stress in the members before fatigue failure increased from 12.08% to 12.3%; when the stress amplitude increased by 70%, the increase of longitudinal steel stress in the test beams increased to 15.5%, and the limit cycling times decreased by more than 66%; corrosion also greatly reduced the fatigue life of the beams and aggravated the deterioration of the beams. The fatigue life of reinforced concrete beams with corrosion rate of about 5% is 34.9% lower than that of non-corroded beams under the same design load stress level. The strain growth rate of longitudinal reinforcement and concrete before fatigue failure is higher than that of non-corroded beams. By summarizing the results of this study and similar tests, it is concluded that there is no risk of fatigue failure for the corroded beams with 5% corrosion rate of longitudinal bars and uncorroded beams at the same stress level, and the risk of fatigue failure for the corroded beams at the later stage of operation under the load stress level is investigated. Under the influence of various factors, the limit value of stress given in the code for concrete design in China can not meet the requirements of actual bridges under the actual load and corrosion conditions.
【学位授予单位】：交通运输部公路科学研究院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U441.4
本文编号：2229287
[Abstract]:Fatigue, as an important inducement of brittle failure of structures, has attracted much attention in the engineering field. With the increase of traffic flow and density, fatigue problems of concrete bridges gradually appear. The fatigue deterioration of bridge structures is further aggravated by the influence of environmental erosion factors. Based on the research and calculation of fatigue load and stress state of actual bridge, the fatigue test of reinforced concrete beams under design load and investigation load is carried out, and the design load stress water is carried out considering the influence of environmental factors. The fatigue test of corroded reinforced concrete beams under flat condition is carried out. The influence of stress level and environmental factors on the fatigue limit cycles and strain evolution of concrete beams is compared and analyzed. In this method, the damage of concrete and steel bar caused by fatigue and environmental factors is considered, the difference between the fatigue stress calculation method and material layer is reflected by strip method, and the joint work of steel bar and concrete and the distribution characteristics of strain in reinforced concrete flexural members are reflected. The strain compatibility relationship between concrete and reinforcement takes into account the deterioration of bond strength between reinforcement and concrete; the influence of damage caused by fatigue and corrosion on the constitutive relationship of concrete and the effective bearing area of reinforcement is introduced; the degradation of bond strength caused by corrosion is considered by the bond force-slip curve of bond element, and the degradation of bond strength caused by corrosion is considered in ANSYS software platform. The finite element simulation of the fatigue behavior of reinforced concrete beams under the combined action of environment and load is realized, and the influence law of stress level and corrosion on the fatigue behavior of reinforced concrete beams is further revealed. Finally, on the basis of summarizing the existing experimental and theoretical research results, the reinforced concrete beams under the combined action of environment and load are mixed. The main conclusions of this study are as follows: through the fatigue stress checking calculation of small and medium span reinforced concrete bridges, the actual bridge meets the requirements of the code under the design load stress level of the current highway bridge design code, and under the actual investigation load, it does not meet the requirements of the code; The fatigue damage mechanism of reinforced concrete beams is different from that of materials. The fatigue damage of reinforced concrete flexural members can be divided into two stages. The early stage of fatigue life (about 10% of the total life) is mainly controlled by the fatigue damage of concrete in the compressive zone, while the longitudinal damage of steel caused by fatigue (represented by steel). The increase of stress level accelerates the fatigue damage and deterioration of the components. After the increase of stress level, the fatigue life decreases greatly, but the deterioration degree of the components before the fatigue failure is comparable. When the stress amplitude increases from 20% of the design load to the stress level of the investigated load, The ultimate cycling times of the test beams decreased by 31.2%~44.6%, and the increase rate of steel stress in the members before fatigue failure increased from 12.08% to 12.3%; when the stress amplitude increased by 70%, the increase of longitudinal steel stress in the test beams increased to 15.5%, and the limit cycling times decreased by more than 66%; corrosion also greatly reduced the fatigue life of the beams and aggravated the deterioration of the beams. The fatigue life of reinforced concrete beams with corrosion rate of about 5% is 34.9% lower than that of non-corroded beams under the same design load stress level. The strain growth rate of longitudinal reinforcement and concrete before fatigue failure is higher than that of non-corroded beams. By summarizing the results of this study and similar tests, it is concluded that there is no risk of fatigue failure for the corroded beams with 5% corrosion rate of longitudinal bars and uncorroded beams at the same stress level, and the risk of fatigue failure for the corroded beams at the later stage of operation under the load stress level is investigated. Under the influence of various factors, the limit value of stress given in the code for concrete design in China can not meet the requirements of actual bridges under the actual load and corrosion conditions.
【学位授予单位】：交通运输部公路科学研究院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U441.4
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