【作者】 王文华；

【导师】 张建仁；

【作者基本信息】 长沙理工大学 ， 桥梁与隧道工程， 2004， 硕士

【摘要】 随着交通建设的快速发展,混凝土斜拉桥日益增多,而结构在施工期的平均风险远高于使用期,因此研究混凝土斜拉桥施工期抗力具有十分重要的理论价值和现实意义。 影响施工期抗力的主要影响因素为混凝土的早期力学性能,本文在现场取样和室内试验的基础上,对施工现场混凝土的早期力学性能进行了统计分析。建立了早龄期混凝土轴心抗压强度和弹性模量的截口概率分布模型,研究了早龄期混凝土轴心抗压强度和弹性模量平均值及其变异系数的经时变化规律以及早龄期混凝土轴心抗压强度和弹性模量的关系。 介绍了计算施工期构件抗力标准自相关函数的两种方法:离散采样法和假定抗力服从独立增量过程的连续函数法。结合实例对两种方法的计算结果进行了分析和比较,发现施工期早期抗力不同时刻的自相关性较强,假定抗力服从独立增量过程的计算结果较离散采样法的结果偏小。如有足够准确度和数量的离散采样数据,用离散采样法可达到足够的精度和要求;用假定抗力服从独立增量过程的连续函数法,其计算结果比实际值偏小。 提出了“施工目标期”的概念,并对施工期抗力与使用期抗力的不同和联系之处进行了论述。在充分考虑施工期特点的基础上,以某一预应力混凝土斜拉桥为背景,建立了混凝土斜拉桥受弯构件施工期早期抗力平均值和早期抗力变异系数随时间变化的概率模型,并进行了参数敏感性分析,结果表明施工期早期抗力的变异系数较大,混凝土早龄期强度对施工期抗力变异系数的影响最大,应在施工中严格控制,而钢筋强度不定性对施工期结构抗力变异系数的影响很小,在施工期抗力和可靠度分析时可作为定值处理。更多还原

【Abstract】 With the rapid development of transportation construction, concrete cable-stayed bridges are more and more, while average risk during construction is more than that in service. So the research on resistance during construction is important.The main factor of resistance during construction is the early mechanical properties of concrete. On the basis of spot sample and laboratory experiment, this paper studies the early mechanical properties of concrete. Probability distributions of early strength and elastic modulus of concrete .are set up. Time-variant models of mean and variation. coefficient of early strength and elastic modulus are developed respectively. Also the relationship between the early strength and elastic modulus of concrete is developed.The two methods of calculating the standard auto-correlation function are introduced: the method of discreteness data and the method of continue function assuming resistance belonging to independent increment random process. According to the two methods, the values of standard auto-correlation function of resistance during construction are calculated respectively, and it is found that auto-correlations of resistance during construction are stronger, and the values of the standard auto-correlation function based on assuming resistance belonging to independent increment random process are less than the results of on discreteness data. If enough accurate and much data are obtained, the latter can reach enough requirement. The values of the standard auto-correlation function based on assuming resistance belonging to independent increment random process are less than the accurate results.The concept of "construction target period " is put forward. The difference between construction and service period is discussed. Considering the characters of construction period, the probability models of mean and variation coefficient of early resistance for flexural member of cable-stayed bridge are set up. The sensitivities of the parameters which can influence the resistances are also analyzed, and it is found that variation coefficient of early resistance during construction is larger, and the influence of early strength of concrete on variation coefficient of resistance during construction is the most. So it is strictly controlled during construction. The influence of the uncertainty of reinforcement strength on variability coefficient of resistance is the least. So it can be as更多还原