连续刚构桥悬臂施工过程中混凝土徐变效应分析
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摘要
徐变是混凝土固有的特性。由于混凝土徐变的复杂性和其对结构影响的重要性,混凝土徐变研究已有一个世纪的历史,但仍然是当今研究的热门课题之一。
在连续刚构桥的建造过程中,混凝土徐变是一个不容回避的技术难题。混凝土的徐变变形能导致连续刚构桥在施工过程中的应力监测结果产生很大的误差,也使得桥梁的线形控制效果难以得到保证。本文就此对连续刚构桥悬臂施工过程中混凝土的徐变进行探究,寻求能计算施工过程中混凝土徐变效应的方法。主要工作如下:
(1)介绍了混凝土徐变的影响因素、徐变模型和主要的徐变计算理论并对我国规范JTGD62-2004《公路钢筋混凝土及预应力混凝土桥涵设计规范》提出的混凝土徐变系数计算公式进行了参数敏感性分析,发现环境年平均相对湿度和混凝土强度对徐变系数的影响比其他两参数显著,有助于提高后续徐变计算的精确性。
(2)从力学的科学角度出发,钢筋混凝土构件与相同尺寸的素混凝土构件在相同的荷载作用下,两者的变形差异是由钢筋对混凝土的附加内力导致的。根据混凝土徐变计算公式、力平衡条件和位移协调条件推导考虑钢筋影响的混凝土徐变计算公式,并通过算例验证公式的正确性。
(3)连续刚构桥悬臂施工过程中,T构为静定结构,混凝土徐变应变不引起结构应力的变化。为了能够正确的分析判断桥梁结构的受力状态,必须计算出施工过程中混凝土的徐变应变,并从现场测试的应变值中扣除出来,以达到对结构应力进行修正的目的。本文根据徐变相关理论和叠加原理,针对连续刚构桥悬臂施工的方法提出应力结果修正公式,并运用到浑水河大桥主桥的应力监测中,验证了该方法的有效性。
(4)根据按龄期调整有效模量徐变计算理论和叠加原理,提出T构各截面混凝土徐变引起悬臂端挠度计算公式。运用该公式计算出浑水河大桥主桥悬臂施工过程中混凝土徐变引起合拢前悬臂端部的总挠度值。并根据计算结果对预拱度进行修正,保证了桥梁的顺利合拢和线形控制良好。
Creep is an inherent property of concrete. Because of the complexity and important influence for structures, the study on concrete creep can trace back to 100 years ago but it is still a hot research topic now.
During the construction of continue rigid frame bridges, creep is a technical problem that can not be avoided. Creep can lead to errors of the stress monitoring during the construction of continue rigid frame bridges and make the line of the bridge hard to control. Based on this background, the paper did some research in the creep to seek ways for calculating the its effect during the cantilever construction of continue rigid frame bridges. The main work is as follow:
(1) The paper introduced the influence factors, creep models, and the calculation methods of creep. The sensitivity of each parameter of the creep coefficient formula in our country's norm- JTGD62-2004 "Highway of reinforced concrete and prestressed concrete bridge and culvert design specification" was analyzed and drew a conclusion that the influences of the average relative humidity and the strength of concrete for creep were much more significant than the other parameters'.
(2) From the mechanical point of view, the deformation caused by the same load in reinforced concrete structure and the same size concrete structure is different, because of the additional internal force between reinforcing bars and concrete. Based on the force equilibrium and deformation coordination, the paper deduced the method of creep calculation considering the influence of reinforcing bars. The method was proved to be correct by an example.
(3) During the cantilever construction of continue rigid frame bridges, the structures are statically determinate, so the creep doesn't lead to the increase of stress. In order to analyze the force status of the bridge structures correctly, the creep should be calculated and deducted from the stain tested by strain sensor. Based on creep theory and principle of superposition, the paper deduced the stress correction formula for the construction of continue rigid frame bridges. The formula was used in the stress monitoring for the Hun Shuihe Bridge, and was proved to be effective.
(4) Based on the creep calculation method called "By Age-Adjusted Effective Modulus Method" and principle of superposition, the paper deduced a formula of calculating deflection caused by creep. The deflection of Hun Shuihe Bridge caused by creep during its construction was calculated using this formula and the construction pre-camber was adjusted to guarantee the lines of the bridge.
在连续刚构桥的建造过程中,混凝土徐变是一个不容回避的技术难题。混凝土的徐变变形能导致连续刚构桥在施工过程中的应力监测结果产生很大的误差,也使得桥梁的线形控制效果难以得到保证。本文就此对连续刚构桥悬臂施工过程中混凝土的徐变进行探究,寻求能计算施工过程中混凝土徐变效应的方法。主要工作如下:
(1)介绍了混凝土徐变的影响因素、徐变模型和主要的徐变计算理论并对我国规范JTGD62-2004《公路钢筋混凝土及预应力混凝土桥涵设计规范》提出的混凝土徐变系数计算公式进行了参数敏感性分析,发现环境年平均相对湿度和混凝土强度对徐变系数的影响比其他两参数显著,有助于提高后续徐变计算的精确性。
(2)从力学的科学角度出发,钢筋混凝土构件与相同尺寸的素混凝土构件在相同的荷载作用下,两者的变形差异是由钢筋对混凝土的附加内力导致的。根据混凝土徐变计算公式、力平衡条件和位移协调条件推导考虑钢筋影响的混凝土徐变计算公式,并通过算例验证公式的正确性。
(3)连续刚构桥悬臂施工过程中,T构为静定结构,混凝土徐变应变不引起结构应力的变化。为了能够正确的分析判断桥梁结构的受力状态,必须计算出施工过程中混凝土的徐变应变,并从现场测试的应变值中扣除出来,以达到对结构应力进行修正的目的。本文根据徐变相关理论和叠加原理,针对连续刚构桥悬臂施工的方法提出应力结果修正公式,并运用到浑水河大桥主桥的应力监测中,验证了该方法的有效性。
(4)根据按龄期调整有效模量徐变计算理论和叠加原理,提出T构各截面混凝土徐变引起悬臂端挠度计算公式。运用该公式计算出浑水河大桥主桥悬臂施工过程中混凝土徐变引起合拢前悬臂端部的总挠度值。并根据计算结果对预拱度进行修正,保证了桥梁的顺利合拢和线形控制良好。
Creep is an inherent property of concrete. Because of the complexity and important influence for structures, the study on concrete creep can trace back to 100 years ago but it is still a hot research topic now.
During the construction of continue rigid frame bridges, creep is a technical problem that can not be avoided. Creep can lead to errors of the stress monitoring during the construction of continue rigid frame bridges and make the line of the bridge hard to control. Based on this background, the paper did some research in the creep to seek ways for calculating the its effect during the cantilever construction of continue rigid frame bridges. The main work is as follow:
(1) The paper introduced the influence factors, creep models, and the calculation methods of creep. The sensitivity of each parameter of the creep coefficient formula in our country's norm- JTGD62-2004 "Highway of reinforced concrete and prestressed concrete bridge and culvert design specification" was analyzed and drew a conclusion that the influences of the average relative humidity and the strength of concrete for creep were much more significant than the other parameters'.
(2) From the mechanical point of view, the deformation caused by the same load in reinforced concrete structure and the same size concrete structure is different, because of the additional internal force between reinforcing bars and concrete. Based on the force equilibrium and deformation coordination, the paper deduced the method of creep calculation considering the influence of reinforcing bars. The method was proved to be correct by an example.
(3) During the cantilever construction of continue rigid frame bridges, the structures are statically determinate, so the creep doesn't lead to the increase of stress. In order to analyze the force status of the bridge structures correctly, the creep should be calculated and deducted from the stain tested by strain sensor. Based on creep theory and principle of superposition, the paper deduced the stress correction formula for the construction of continue rigid frame bridges. The formula was used in the stress monitoring for the Hun Shuihe Bridge, and was proved to be effective.
(4) Based on the creep calculation method called "By Age-Adjusted Effective Modulus Method" and principle of superposition, the paper deduced a formula of calculating deflection caused by creep. The deflection of Hun Shuihe Bridge caused by creep during its construction was calculated using this formula and the construction pre-camber was adjusted to guarantee the lines of the bridge.
引文
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[2]林波.混凝土收缩效应及其效应的计算分析和试验研究:[硕士学位论文].南京:东南大学,2006
[3]L.Vitek.Long-term deflections of large presterssed concrete bridges.Progress Report,CEB Bulletin No.235.1997
[4]惠荣炎,黄国兴,易冰若.混凝土的徐变.北京:中国铁道出版社,1988.1-50
[5]周履,陈永春.收缩徐变.北京:中国铁道出版社,1994
[6]朱伯芳.朱伯芳院士文选.北京:中国电力出版社,1997
[7]王勋文,潘家英.按龄期调整有效模量法中老化系数x的取值问题.中国铁道科学,1996.17(3):12-22
[8]王书庆.徐变自动增量分析方法及其实现.同济大学学报,2000.28(2):138-142
[9]高政国等.混凝土结构徐变应力分析的全量方法.土木工程学报,2001.34(4):10-14
[10]颜东煌等.混凝土桥梁收缩徐变计算的有限元方法与应用.中国公路学报,2004.17(2)
[11]沈蒲生等.超静定结构徐变效应的力法分析方法.铁道科学与工程学报,2006.3(1)
[12]CEB欧洲国际混凝土委员会.CEB-FIP1978模式规范(混凝土结构).中国建筑科学研究院结构所规范室译
[13]CEB欧洲国际混凝土委员会.CEB-FIP1990模式规范(混凝土结构).中国建筑科学研究院结构所规范室译,1991.1
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[15]交通部.公路钢筋混凝土及预应力混凝土桥涵设计规范(JTGD62-2004).北京:人民交通出版社,2004.
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[24]Pichler,Ch.,Lackner,R.A multiscale creep model as basis for simulation,of early-age concrete behavior.Computer and concrete,2008.5(4):295-328
[25]Cao J,Wang YF.Comparison and anlysis of concrete creep models under wet-dry cycle effect.Proceeding of the 3rd International Conference on the Concrete Future,2008:99-106
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[2]林波.混凝土收缩效应及其效应的计算分析和试验研究:[硕士学位论文].南京:东南大学,2006
[3]L.Vitek.Long-term deflections of large presterssed concrete bridges.Progress Report,CEB Bulletin No.235.1997
[4]惠荣炎,黄国兴,易冰若.混凝土的徐变.北京:中国铁道出版社,1988.1-50
[5]周履,陈永春.收缩徐变.北京:中国铁道出版社,1994
[6]朱伯芳.朱伯芳院士文选.北京:中国电力出版社,1997
[7]王勋文,潘家英.按龄期调整有效模量法中老化系数x的取值问题.中国铁道科学,1996.17(3):12-22
[8]王书庆.徐变自动增量分析方法及其实现.同济大学学报,2000.28(2):138-142
[9]高政国等.混凝土结构徐变应力分析的全量方法.土木工程学报,2001.34(4):10-14
[10]颜东煌等.混凝土桥梁收缩徐变计算的有限元方法与应用.中国公路学报,2004.17(2)
[11]沈蒲生等.超静定结构徐变效应的力法分析方法.铁道科学与工程学报,2006.3(1)
[12]CEB欧洲国际混凝土委员会.CEB-FIP1978模式规范(混凝土结构).中国建筑科学研究院结构所规范室译
[13]CEB欧洲国际混凝土委员会.CEB-FIP1990模式规范(混凝土结构).中国建筑科学研究院结构所规范室译,1991.1
[14]交通部.公路钢筋混凝土及预应力混凝土桥涵设计规范(JTJ023-85).北京:人民交通出版社,1985
[15]交通部.公路钢筋混凝土及预应力混凝土桥涵设计规范(JTGD62-2004).北京:人民交通出版社,2004.
[16]ACI Committee 209.Prediction of Creep,Shrinkage and Temperature Effects In Concrete Structures(209-82).America Concrete Institute.Detroit,1982
[17]ACI Committee 209.Prediction of Creep,Shrinkage and Temperature Effects In Concrete Structures(209R-92).America Concrete Institute.Farmington Hills,MICH.,1992
[18]Z.P.Bazant,J.Kim.Improved predication model for time-dependent deformations of concrete:Part 2-Shrinkage.Materials and Structures,1991.24:327-345
[19]Z.P.Bazant,J.Kim.Improved predication model for time-dependent deformations of concrete:Part 3-Creep at drying.Materials and Structures,1991.24:327-345
[20]彭卫,杜时贵.混凝土徐变效应的计算机分析.西安:西安公路交通大学,1999
[21]S.Morino,J.K.Wanguchi,Z.S.Cao.Creep Behavior of Concrete Filled Steel Tubular Members.Proc.Of an Engineering Foundation Confer.On Steel-Concrete campsite Structure.ASCE,IRSCE,1996:514-525
[22]Sakata K.Prediction Concrete of Creep and Shrinkage[A].Creep and Shrinkage of Concrete[C].Proceedings of the Fifth International RILEM Symposium Barcelona Spain,1993:649-654
[23]Gardner N J,Lockman M J.Design Provisions for Drying Shrinkage and Creep of Normal-Strength Concrete[J].ACI Materials Journal,2001.98(2):159-167
[24]Pichler,Ch.,Lackner,R.A multiscale creep model as basis for simulation,of early-age concrete behavior.Computer and concrete,2008.5(4):295-328
[25]Cao J,Wang YF.Comparison and anlysis of concrete creep models under wet-dry cycle effect.Proceeding of the 3rd International Conference on the Concrete Future,2008:99-106
[26]余慧平.混凝土徐变与收缩特性现场试验研究.铁道建筑技术,1997
[27]盛兴旺,杨建中.预应力混凝土组合梁徐变应力重分布.桥梁建设.2003年04期,11-14
[28]Z.P.Bazant,Murphy,W.P.Creep and shrinkage prediction model for analysis and design of concrete structure-model B3.Mater.Struct,1995.28(1):357-365
[29]Z.P.Bazant,Li GH.Unbiased Statistical Comparison of Creep and Shrinkage Prediction Models.ACI Materials Journal,2008.105(6):610-621
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