夏季高原干旱地区铁路桥墩大体积混凝土防裂技术研究

发布时间：2018-07-13 16:40

【摘要】：西北高原地区气候干旱、昼夜温差大、季节特征比较明显，大体积混凝土的温度场和应力场受环境因素的影响又比较大，而且目前专门针对桥墩大体积混凝土的研究还比较少，既有的施工方法和经验不能完全适用于西北高原环境。随着西北地区高速铁路的全面建设，大量的大体积混凝土桥墩和基础出现在铁路桥梁的建设中，但是，大体积混凝土结构在施工以及服役的过程中要出现裂缝，这是一个不争的事实，因此，如何采取有效的施工方法和养护措施来减少这些危害裂缝的产生是迫切需要解决的问题。本文以青藏铁路西格二线西宁特大桥桥墩大体积混凝土工程为依托，利用有限元分析软件MIDAS/FEA分析了桥墩施工及养护期间混凝土的温度场和温度应力，并且从影响大体积混凝土温度场和温度应力的一些敏感性参数出发，探讨夏季高原干旱地区铁路桥墩大体积混凝土施工的防裂技术对策。其研究内容主要包括以下方面：（1）总结和学习大体积混凝土温度场和应力场的理论知识，介绍混凝土热力学参数的选取方法，主要包括混凝土的导热系数、导温系数、对流系数、热源函数等。（2）利用MIDAS/FEA对夏季施工的28#桥墩混凝土的温度场和温度应力进行仿真分析，给出桥墩混凝土温度和应力的时程曲线，并详细分析《大体积混凝土施工技术规程》（GB50496-2009）所规定的温控指标，，包括混凝土的温升峰值、里表温差、混凝土表层与环境气温间的温差、降温速率等。（3）整理和分析现场实验数据，总结出夏季大体积混凝土温升曲线。同时，根据现场实测数据，利用传统的经验公式对温度场进行了估算。最后通过估算值、有限元计算结果与实测值进行对比，验证MIDAS/FEA仿真分析的可靠性、有效性。（4）从影响大体积混凝土温度场和温度应力的一些敏感性因素入手，紧紧围绕高原干旱地区、夏季施工这一特点，研究适用于夏季高原干旱地区铁路桥墩大体积混凝土施工的防裂技术措施。
[Abstract]:In the northwest plateau, the climate is dry, the temperature difference between day and night is large, the seasonal characteristic is obvious, the temperature field and stress field of mass concrete are influenced by environmental factors, and the research on mass concrete of bridge pier is relatively few at present. The existing construction methods and experience can not be fully applied to the northwest plateau environment. With the overall construction of high-speed railway in Northwest China, a large number of mass concrete piers and foundations appear in the construction of railway bridges. However, cracks will appear in the construction and service of mass concrete structures. This is an indisputable fact, therefore, how to take effective construction methods and maintenance measures to reduce the occurrence of these harmful cracks is an urgent problem to be solved. In this paper, the temperature field and thermal stress of concrete during the construction and maintenance of bridge pier are analyzed by using the finite element analysis software Midas / FEA, based on the mass concrete project of Xining super bridge pier on the second line of Qinghai-Tibet Railway. Based on some sensitive parameters which affect the temperature field and thermal stress of mass concrete, the crack prevention technology of railway pier mass concrete construction in arid area of plateau in summer is discussed. The main research contents are as follows: (1) summarize and study the theoretical knowledge of temperature field and stress field of mass concrete, introduce the method of selecting thermodynamic parameters of concrete, mainly include the thermal conductivity of concrete. Temperature conductivity coefficient, convection coefficient, heat source function, etc. (2) temperature field and temperature stress of concrete of 28 # bridge pier constructed in summer are simulated and analyzed by midas / FEA, and the time history curve of temperature and stress of pier concrete is given. The temperature control indexes stipulated in "Technical Specification for Mass concrete Construction" (GB50496-2009) are analyzed in detail, including the peak temperature rise of concrete, the temperature difference on the inside surface, and the temperature difference between the surface layer of concrete and the ambient temperature. (3) consolidation and analysis of field experimental data, summing up the temperature rise curve of mass concrete in summer. At the same time, based on the field measured data, the temperature field is estimated by using the traditional empirical formula. Finally, the reliability and validity of MIDAS-FEA simulation analysis are verified by comparing the estimated values, finite element results and measured results. (4) some sensitive factors affecting the temperature field and thermal stress of mass concrete are discussed. Focusing on the characteristics of the construction in the arid area of the plateau in summer, this paper studies the crack prevention technical measures suitable for mass concrete construction of the railway pier in the arid area of the plateau in summer.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U445.57

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