学科：桥梁与隧道工程,出版时间：2018,导师：杨永清指导,学位授予单位：西南交通大学,论文作者：鲁薇薇著,
中文
近二十年来，为适应大规模交通基础设施建设快速发展需要，对预应力混凝土(PC)连续梁和钢管混凝土(CFST)拱组合体系桥梁研究主要集中在结构参数设计、优化及工艺技术等方面。随着我国高速铁路发展和铁路由大规模建设逐渐转向体系安全运营与维护，准确把握桥梁结构长期性能成为铁路桥梁特别是高速铁路桥梁面临的重要课题。PC连续梁与CFST拱组合体系桥梁的受力变形状态、梁拱协同受力性能等在徐变影响下随时间不断演变。深入认识和准确把握徐变对桥梁结构行为的影响，是发展完善更为科学合理的设计分析、施工控制和维护技术方法的基础，对发挥该类桥梁的结构优势，确保桥梁长期稳定可靠工作状态和运行安全，有重要意义。 本文结合铁道部科技研究开发计划重大项目子课题“京沪高速铁路(90+180+90)m连续梁拱桥收缩、徐变影响试验研究(2008G031-K)”，针对工程结构实际工作环境下普通混凝土(OC)和CFST徐变行为及其预测方法进行系统研究，并将获得研究成果应用于依托桥梁结构的徐变效应分析中。本文主要的研究工作和研究成果如下： (1)对变温、湿度条件下OC徐变试验、CFST徐变试验、OC和CFST徐变预测方法及徐变对梁拱组合体系桥梁结构行为的影响规律等研究领域尚存在问题和值得深入研究课题进行总结。 (2)将研究基础薄弱的自然环境条件下OC和CFST徐变行为规律作为试验研究主要内容。以尽量贴近工程实际为目标，对试件的用材、形状及尺寸、含钢率、加载应力和加载龄期等试验参数的设计方法进行研究。基于杠杆原理，研制出适用于户外气候条件且加载吨位可达200 t的徐变加载装置。测试得到自然环境条件下OC和CFST收缩、徐变试件在3年多时间内发展规律曲线。基于测试数据，分析OC和CFST徐变试件上各类变形之间相互关系及其占总变形比例随时间的演变规律，对比分析不同加载龄期OC和CFST试件的徐变行为差异。 (3)通过对试验数据和现行徐变模型进行比较，分析随机变化温、湿度环境对OC徐变行为的影响规律。引入基准徐变(系数)、湿度徐变(系数)和温度徐变(系数)概念，分别定义温、湿度恒定条件下OC徐变和环境湿度、温度变化引起的OC徐变随时间发展规律，提出适用于预测随机变化温、湿度条件下OC徐变的组合徐变模型。结合试验数据和既有徐变模型，探讨温、湿度徐变系数定量方法，并通过引入有效时间和衰减时间，提出大气温度环境下温度徐变系数实用计算公式。基于试验数据和已有成果，验证表明组合徐变模型预测效果和温度徐变系数实用公式计算精度均较理想。 (4)基于试验数据，讨论CFST和OC在徐变行为上共性、差异及相应成因。分析由于徐变现象导致的CFST试件钢管与核心混凝土之间的荷载转移规律和应力重分布规律。基于试验数据和既有CFST、OC徐变模型的比较结果，在ACI209(92)模型和B3模型基础上，分别引入CFST构件工作状态校正系数和钢管参与作用影响系数，提出CFST徐变系数预测模型。 (5)将本文提出组合徐变模型和CFST徐变试验结果应用于跨径(90+180+90)m的PC连续梁与CFST拱组合体系桥梁的徐变效应分析中。基于目前通用桥梁有限元程序和计算机语言，提出便于工程应用的基于本文徐变计算方法的桥梁结构徐变效应分析方法。通过对应用本文徐变计算方法和依据中铁05桥梁规范分析得到的关键施工阶段和运营期间的结构位移、应力和内力结果进行比较，探讨由于忽略桥址处环境温度变化对徐变影响和尚存在的CFST徐变预测问题，可能导致的人们对工程结构行为的认知偏差。 关键词：梁拱组合体系桥梁；徐变；预应力混凝土；钢管混凝土；试验；结构行为；自然环境条件
英文
To assist the large-scale railway infrastructure construction in China, researches on prestressed concrete (PC) continuous beam and concrete-filled steel tube (CFST) arch bridges have been mainly focused on structural parameters design, optimization, construction technology, in the last two decades. With the developmemt of the high-speed railway system and the transition from the large-scale new construction to the long-term safe operation and maintenance of railway systems, it is of vital importance to completely and accurately comprehend the long-term performance of high speed railway bridges. Under the influence of creep, the stress and deformation states of PC continuous beam and CFST arch bridges change with time. In order to provide more scientific and reasonable design, construction control and maintenance methods, and to keep structure in good working order and driving condition, it is necessary to study the influence of creep on the structural performance of PC continuous beam and CFST arch bridges. The creep behavior of ordinary concrete (OC) and concrete in CFST under the on-site working conditions and its prediction methods were systematically studied in this thesis. Research results were applied to analyze the creep effects of an actual bridge. This thesis project is supported by the Ministry of Railways Science and Technology Research and Development Program Fund of China, under the Project No.2008G031-K “Experimental study of the influence of shrinkage and creep on (90+180+90) m beam-arch bridges on Beijing-Shanghai High-speed Railway Line”. The main research works and research results are as follows: (1)Based on the literature review, the existing knowledge gap was identified in the creep behavior of OC under variable temperature and humidity conditions, creep behavior of CFST, the creep prediction methods of OC and CFST, as well as the effects of concrete creep on beam-arch bridges. (2)The objective of the experiment program was to study the creep behavior of OC and concrete in CFST under natural environment, which has a very limited understanding in the literature. In the testing program, the following parameters were included: the material and shape and size of specimens, steel ratio, stress level and loading age of (core) concrete. The creep loading equipment suitable for outdoor climate conditions and the loading capacity up to 200 t were designed based on the lever principle. The curves of shrinkage strain and creep strain development of OC specimens and CFST specimens under natural environment for a period of approximately three years were obtained. The test data was utilized to investigate the change of the relationship between various deformations on the specimens and its proportion, and to compare and analyze the distinctions between creep specimens with different loading ages. (3)The influence of random variations of temperature and humidity on the creep behavior of OC was investigated by comparing between the test results and the predicted results given by the existing creep models. Benchmark Creep Coefficient was introduced to describe the creep behavior of the OC under constant temperature and humidity conditions. Humidity Creep Coefficient and Temperature Creep Coefficient were introduced to describe the development of additional creep caused by the variation of ambient temperature and ambient humidity, respectively. Combination Creep Model for predicting the creep behavior of OC exposed to random variation of temperature and humidity environments was proposed based on Benchmark Creep Coefficient and Humidity Creep Coefficient and Temperature Creep Coefficient. Combined with the experimental data and the existing creep models, the quantitative methods of Humidity Creep Coefficient and Temperature Creep Coefficient were discussed. The practical formulas for Temperature Creep Coefficient were presented by introducing Effective Time and Decay Time, which were used to characterize the durability and attenuation features of the effect of temperature variation on creep behavior of ordinary concrete, respectively. The experimental data indicated that Combination Creep Model and the practical formulas for Temperature Creep Coefficient are reasonable and effective. (4)Based on the test data, the difference and similarity in creep behavior between CFST and OC were discussed. The regular patterns of the loading transfer and the stress redistribution between the core concrete and steel tube of CFST specimens caused by the creep of core concrete were investigated. The test results of CFST creep specimens and the predicted results given by the existing creep models for OC and CFST were compared and analyzde. On the basis of the ACI209 (92) model and B3 model, the prediction models of the creep coefficient for concret in CFST were presented by introducing Correction Factors of working condition of CFST members and the Interaction Influence Coefficient. (5)Combination Creep Model and the creep test results of CFST were applied to analyze the creep effects of (90+180+90) m PC continuous beam and CFST arch bridges. The analysis method of creep effects of bridge structures, based on the creep calculation method presented in this thesis, was provided for practical engineering applications. It is concluded that it is important to consider the effect of actual temperature on creep of concrete. The existing issues in the prediction of creep for concrete in CFST were also discussed based on the analysis results of displacement, stress and internal force of the bridge structure during critical construction stages and operation. In the end, the comparison between the proposed method in this thesis and the current specification for railway bridges was discussed. Key words: beam-arch association bridges; creep; prestressed concrete; concrete filled-steel tube; experiment; structural behavior; natural environment-condition
