混凝土矩形空心墩温度作用及竖向开裂问题研究
发布时间：2018-08-29 15:33
【摘要】：我国现行公路桥梁设计规范对于混凝土桥梁均匀温度作用的规定较为粗略,与全国范围内差异甚大的气候条件之间存在一定矛盾;目前国内针对混凝土矩形空心墩非均匀温度作用的系统性研究成果也相对较少,不便于设计分析人员参考使用;另外不少混凝土矩形空心墩出现了竖向开裂病害,目前系统性的成因分析和裂缝控制研究还较为缺乏。本文通过试验研究与数值模拟相结合的方法,对混凝土矩形空心墩的温度作用取值、温度效应计算的关键参数以及竖向开裂的机理和防治措施进行了深入研究,主要研究工作和结论如下:基于温度长期观测资料,系统研究了混凝土空心墩平均温度与外气温的关系,提出了两种根据气温资料预测空心墩平均温度变化范围的方法,通过对试验桥墩在观测期内平均温度变化范围的预测,发现在最高、最低日平均气温的基础上增加2oC时得到的温度变化范围与预测范围基本吻合;参照欧洲结构设计标准,建议取50年重现期的最高、最低日平均气温作为基本气温,在基本气温的基础上增加2oC得到混凝土桥梁有效温度的标准值,通过统计分析,得到了全国194个气象站混凝土桥梁有效温度的推荐值,并与现行公路桥梁设计规范进行了对比分析,指出了其不足之处,并提出了有关混凝土桥梁均匀温度作用的建议。基于温度长期观测资料,系统研究了混凝土空心墩正温差、负温差作用与气象条件的关系;通过对混凝土矩形空心墩日照温度场和寒潮降温温度场的实测和有限元模拟,提出了混凝土矩形空心墩非均匀温度作用的二维温差分布模式和沿壁厚方向的幂函数温差分布曲线;搜集了全国20个代表性地点的大气透明系数、气温日较差、日平均气温24小时最大降温幅度、日平均风速等资料,采用有限元模拟方法,得到了20个代表性测站的最大壁面正温差和负温差标准值,并通过拟合计算和综合分析,给出了幂函数常量a和温度变化影响深度b的建议值。对混凝土桥梁温度效应计算的相关关键参数进行了实验研究:设计了一种混凝土试件加热装置,通过直接加热,验证了混凝土变形与温度变化的同步性;通过在能自由变形的混凝土试块中埋入钢弦式应变计,实测太阳辐射作用下试块内部应变分布,验证了温度自应力计算时的平截面假定;提出了一种依靠埋入式混凝土应变计测试混凝土线膨胀系数的简易方法,采用简易方法研究了负温条件对线膨胀系数的影响,发现负温下线膨胀系数出现剧增;利用加热装置配合液压伺服动态疲劳试验机,实测了混凝土温度应力和短期内的应力松弛系数,并对温度应力的折减系数和组合问题提出了建议。采用有限元分析和现场实测相结合的方法,系统分析了水泥水化热效应、混凝土不均匀收缩、壁面负温差和竖向荷载对混凝土空心墩竖向开裂的影响,结果表明:这4大因素的不同叠加作用是导致混凝土空心墩竖向开裂的直接原因;从性质上看,混凝土矩形空心墩竖向裂缝主要属于变形裂缝,防治时应以预防措施和配筋防控措施为主,必要时采取裂缝处治措施。
[Abstract]:Current design codes for highway bridges in China stipulate the uniform temperature effect of concrete bridges roughly, which is in contradiction with the climatic conditions which are quite different nationwide. In addition, many concrete rectangular hollow piers appear vertical cracking defects. At present, the systematic analysis of causes and crack control research is still relatively scarce. This paper combines experimental research with numerical simulation to determine the temperature effect of concrete rectangular hollow piers, the key parameters of temperature effect calculation and vertical opening. The main research work and conclusions are as follows: Based on the long-term observation data of temperature, the relationship between the average temperature of concrete hollow pier and the external temperature is studied systematically, and two methods for predicting the average temperature range of Hollow Pier Based on the temperature data are proposed. According to the European structural design standard, it is suggested that the maximum recurrence period of 50 years should be selected, and the minimum daily mean temperature should be taken as the basic temperature, and 2oC should be added on the basis of the basic temperature. Through statistical analysis, the recommended effective temperature of concrete bridges at 194 weather stations in China is obtained, and compared with the current design code of highway bridges, the shortcomings are pointed out. Suggestions on the effect of uniform temperature of concrete bridges are put forward. The relationship between positive temperature difference and negative temperature difference of concrete hollow pier and meteorological conditions is studied systematically. Based on the measurement and finite element simulation of sunshine temperature field and cold wave cooling temperature field of concrete rectangular hollow pier, a two-dimensional temperature difference distribution model and a power function along the wall thickness direction of concrete rectangular hollow pier are proposed. The data of atmospheric transparency coefficient, diurnal temperature difference, maximum 24-hour cooling range of daily average temperature and daily average wind speed were collected from 20 representative sites in China. Proposed values of power function constant a and temperature effect depth B are given. The key parameters of temperature effect calculation of concrete bridge are experimentally studied. A heating device for concrete specimens is designed, which verifies the synchronization of concrete deformation and temperature change by direct heating. The strain distribution inside the specimen under solar radiation is measured by embedded steel wire strain gauge, which verifies the assumption of plane section when calculating the temperature self-stress. Thermal stress and stress relaxation coefficient of concrete in short term were measured by heating device combined with hydraulic servo dynamic fatigue testing machine, and suggestions on reduction coefficient and combination of thermal stress were put forward. The influence of mud hydration heat effect, uneven shrinkage of concrete, negative temperature difference of wall and vertical load on the vertical cracking of concrete hollow pier is studied. The results show that the vertical cracking of concrete hollow pier is directly caused by the different superposition of these four factors. Preventive measures and reinforcement control measures should be the main treatment measures, and crack treatment measures should be taken when necessary.
【学位授予单位】：长安大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：U443.22
本文编号：2211635
[Abstract]:Current design codes for highway bridges in China stipulate the uniform temperature effect of concrete bridges roughly, which is in contradiction with the climatic conditions which are quite different nationwide. In addition, many concrete rectangular hollow piers appear vertical cracking defects. At present, the systematic analysis of causes and crack control research is still relatively scarce. This paper combines experimental research with numerical simulation to determine the temperature effect of concrete rectangular hollow piers, the key parameters of temperature effect calculation and vertical opening. The main research work and conclusions are as follows: Based on the long-term observation data of temperature, the relationship between the average temperature of concrete hollow pier and the external temperature is studied systematically, and two methods for predicting the average temperature range of Hollow Pier Based on the temperature data are proposed. According to the European structural design standard, it is suggested that the maximum recurrence period of 50 years should be selected, and the minimum daily mean temperature should be taken as the basic temperature, and 2oC should be added on the basis of the basic temperature. Through statistical analysis, the recommended effective temperature of concrete bridges at 194 weather stations in China is obtained, and compared with the current design code of highway bridges, the shortcomings are pointed out. Suggestions on the effect of uniform temperature of concrete bridges are put forward. The relationship between positive temperature difference and negative temperature difference of concrete hollow pier and meteorological conditions is studied systematically. Based on the measurement and finite element simulation of sunshine temperature field and cold wave cooling temperature field of concrete rectangular hollow pier, a two-dimensional temperature difference distribution model and a power function along the wall thickness direction of concrete rectangular hollow pier are proposed. The data of atmospheric transparency coefficient, diurnal temperature difference, maximum 24-hour cooling range of daily average temperature and daily average wind speed were collected from 20 representative sites in China. Proposed values of power function constant a and temperature effect depth B are given. The key parameters of temperature effect calculation of concrete bridge are experimentally studied. A heating device for concrete specimens is designed, which verifies the synchronization of concrete deformation and temperature change by direct heating. The strain distribution inside the specimen under solar radiation is measured by embedded steel wire strain gauge, which verifies the assumption of plane section when calculating the temperature self-stress. Thermal stress and stress relaxation coefficient of concrete in short term were measured by heating device combined with hydraulic servo dynamic fatigue testing machine, and suggestions on reduction coefficient and combination of thermal stress were put forward. The influence of mud hydration heat effect, uneven shrinkage of concrete, negative temperature difference of wall and vertical load on the vertical cracking of concrete hollow pier is studied. The results show that the vertical cracking of concrete hollow pier is directly caused by the different superposition of these four factors. Preventive measures and reinforcement control measures should be the main treatment measures, and crack treatment measures should be taken when necessary.
【学位授予单位】：长安大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：U443.22
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