【作者】 李福如；

【导师】 姜福香；

【作者基本信息】 青岛理工大学 ， 桥梁与隧道工程， 2010， 硕士

【摘要】 近十几年来,伴随着高性能混凝土和高强度钢材的广泛使用,预应力混凝土桥梁不断向大跨、轻型、高性能方向发展,极大地推动了我国的桥梁建设事业的进步。目前,预应力混凝土桥梁已在国内外公路桥梁建设中占有主导性的地位。同时我们也应该看到,随着桥梁事业的持续快速发展以及桥梁服役时间的推移,桥梁结构性能退化、承载力不足等问题日益严峻,预应力混凝土桥梁结构现状分析及剩余承载力评定问题显得日渐紧迫。所以,对在役预应力混凝土桥梁结构进行深入的研究具有重要的意义。本文以青岛胶州湾高速公路(海域段)一座服役14年的预应力简支斜交空心板梁桥为研究背景,结合现场及室内试验数据,借助有限元分析程序,对该桥的耐久性现状和剩余承载力进行了相应评价,为此类桥梁的评估提供一定参考。对在役混凝土桥梁耐久性主要影响因素的发生机理、理论模型作了详细介绍,在此基础上,对现状结构的预应力混凝土梁体进行取芯,试验测试了碳化深度、氯离子含量及分布、混凝土抗压强度,并运用相应耐久性预测模型对服役期内碳化深度、抗压强度发展规律进行了预测。结果表明,结构在服役其内耐久性较好,但边梁支座处钝角位置氯离子含量较高,成为结构耐久性的薄弱点。基于应力释放法,现场对单梁构件梁底四分点及跨中位置进行应力释放试验,计算得到梁体在自重及预应力作用下,梁底混凝土的现存应力值。对单梁现状进行了实体模型有限元分析,以应力释放试验结果验证了模型的合理性;进一步考虑长期服役后材料的劣化,进行了单梁极限承载力非线性分析,最终反算并评定了单梁现状及长期服役后的承载力情况,分析发现,长期服役后,结构的极限承载力降低并不明显;以跨中梁底混凝土不出现拉应力为极限状态的单梁承载力值,不满足现行规范按承载力极限状态设计时基本组合的要求;以跨中梁底混凝土不出现受拉裂缝为极限状态的单梁承载力值可以满足基本组合的要求,但安全储备较小。对大地激励下的结构自振特性进行现场测试,采集结构自振频谱,运用自谱及互谱分析得到现状结构的一阶自振频率;用梁格法建立了全桥上部结构模型,结合试验所得一阶频率值,对结构刚度进行评定,结果表明,现状结构仍有一定刚度储备;以不同工况模拟结构铰缝损伤及材料劣化,分析了结构自振特性的变化规律。分析发现,相同程度下,跨中损伤对结构自振频率影响大于四分点位置,而且高阶频率的敏感性较高。考虑材料劣化的长期性,在短期内,混凝土强度的变化对结构自振特性的影响并不明显。更多还原

【Abstract】 In nearly ten years,with the widely used of high-performance concrete and high strength steel, Prestressed concrete bridges have continuously developed towards the direction of long-span, light and high-performance which greatly promote China’s bridge construction. Prestressed concrete bridge today boasts its dominant position in highway bridge field in our country. At the same time, with its continued rapid development and the elapse of serviced time, we must see the increasingly serious situation in degeneration of bridge’s property, insufficient bearing force, etc. Therefore, it becomes increasingly urgent to analyze the present condition and assess the carrying capacity of prestressed concrete bridge structure. Thus, it has significant meaning to have an in-depth study of the prestressed concrete bridge structure in service.This paper aims at evaluating the present durability and over carrying capacity by using the finite element analysis program and the scene and indoor experimental data on the background of a simple-supported prestressed concrete core slab bridge which has serviced for 14 years in Jiao Zhou bay expressway of Qingdao, which would offer reference for future similar.There are introduced in detail about the mechanism and theoretical models of the main factors of the existing concrete bridge durability. On this basis, some samples obtained by the current structure of prestressed concrete beams. the carbonization depth, Chlorine ion content and distribution and compressive properties of these concrete samples be tested and the corresponding durability prediction model is used to forecasted the development rule during service period. The test results showed that the bridge bridge durability, but the weak point of the durability was chlorine ion content at the position of beam orer obtuse Angle.The stress was released at the quartile and middle of the beam. Based on the method of stress release,existing stress value of the concrete under the beam could be obtained under the gravity and prestressing. The physical model of monospar was analysed by finite element method, and the model was proved reasonable. Deterioration of the material after long-term service was taken into the account, and the ultimate bearing capacity was analysed by the nonlinear mothed. The bearing capacity of monospar at current situation and after long term service were obtained and assessed. The results indicated that the ultimate bearing capacity of the structure was not significantly reduced after long-term service. The ultimate bearing capacity of monospar where tensile stress does not appear to limit state did not meet the requirements according to the fundamental combination. There is no cracks formed by tensile stress, with which as the standard, the bearing capacity of monospar could meet requirements. However, safety reserve was small.The test of the structure self-oscillation characteristics was taking on the scene under the earth self-oscillation. It collects natural frequency of vibration and uses spectral analysis and cross-spectral analysis to get the first natural frequency of vibration; Established the superstructure model of the whole bridge in grillage method, combined with test value of first-order frequency, to assess structure stiffness. Results showed that, there is still a certain status structure stiffness reserves. Analyzes the variation law of structure vibration characteristics under different conditions simulation of damage and material degradation. Analysis found that, midspan damage on structure vibration frequency influence greater than four fold point of span in the same degree, and it has had the higher susceptibility of higher-order frequency. In the short term, the effect is not obvious of structure vibration characteristics as a result of strength of concrete changes of considering long-term of the material degradation.更多还原