混凝土温度应力的实验测定
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摘要
通过混凝土应变计等观测仪器来监测结构的应力状态,一直是研究复杂结构工作性态和检验计算结果正确性的重要手段,也是大型重要工程在线监测预警预报的主要方法。但基于混凝土应变计观测数据的温度应力解析方法,至今未能得到解决,使大量观测数据得不到合理分析,因而观测仪器不能发挥其应有的在线监测预警预报作用,本文的主要目的是对基于混凝土应变计实测数据的温度应力分析方法进行初步研究。
本文对固端约束及弹性约束状态混凝土试件的温度应力进行了试验测定。混凝土试件为直径105mm、高度370mm圆柱体,内部中心位置埋设混凝土应变计和温度传感器,试件外侧缠绕电热带,电热带外侧用绝热性能良好的聚氨酯泡沫填缝剂密封。试验过程中,试件的升温幅度由温度传感器控制,试件的变形用内埋式混凝土应变计和外设千分表测定,温度应力用荷载传感器测定。
对混凝土试件升温较传统的做法是使用水浴或油浴进行加热,在试验中自行设计了电热带加热方案及相应的保温措施,使得给混凝土试件提供较为均匀的温度荷载时,还可以方便地使用约束装置以满足相关条件的模拟。结果表明:
(1)自行设计的电热带加热方案能够给混凝土试件施加较为均匀的温度荷载,升温幅度可达70℃;
(2)在固端约束及弹性约束状态下,温度应力与温度变化之间具有良好的线性关系,混凝土应变计的应变变化与温度应力之间也存在良好的线性关系,但温度应力的实测值远小于理论值。
(3)在约束程度较强,温度场均匀变化时,使用混凝土应变计测定温度应力可以取得较理想的效果。
Through the concrete strain gauges and other observation instruments to monitor the stress state of the structure , has been an important tool to study the work state of the complex structure and verify the correctness of the calculation results , but also an primary method of the early warning and forecasting of the important project. However, the method of thermal stress analysis based on observations of the concrete gauges has not been resolved, so that a large number of observational data cannot be analyze reasonably ,and the observing instruments cannot play their due role in the online monitoring and early warning forecasting. The main purpose of this paper is to analyze the thermal stress based on the measured data of the concrete strain gauge preliminarily.
The thermal stress of the concrete specimen with fixed and elastic restraints at both ends was measured by applying the temperature load on the specimen with an electric heater cable .The concrete specimen is a cylinder with 370mm in height and 105mm in diameter and fixed by the load distribution plates of the testing machine, a vibrating wire strain gauge and a temperature sensor were buried in the center of the specimen, the electric heater cable was wrapped on the lateral surface of the specimen, which was sealed with a layer of polyurethane foam with excellent heat insulating property. In the process of the experiments, the temperature rise was controlled by the temperature sensor, the thermal deformation of the specimen was measured by both embedded vibrating wire strain gauge and the dial gauges installed on the test machine, and the thermal stress was detected by the load sensor.
The concrete specimens are heated in water or oil traditionally; In the test a heating cable program and an insulation system are designed, Which provide a more uniform temperature load and the easily use of restraint setup to meet the conditions of the simulation for concrete specimens.
The results showed that:
(1) The heating cable heating program designed can supply an uniform temperature load to the concrete specimens , a 70℃of the temperatures rise can be reached;
(2) In the state of ends restraint, the thermal stress produced in the specimen is linearly dependent on the temperature rising, and the strain changes measured by the strain gauge is also linearly correlate to the thermal stress, but the measured values of the thermal stress are much smaller than theoretical ones.
(3) In the state of ends restraint strongly and the temperature field changes uniformly, approximate results can be obtained by using the concrete strain gauge to measure the thermal stress.
本文对固端约束及弹性约束状态混凝土试件的温度应力进行了试验测定。混凝土试件为直径105mm、高度370mm圆柱体,内部中心位置埋设混凝土应变计和温度传感器,试件外侧缠绕电热带,电热带外侧用绝热性能良好的聚氨酯泡沫填缝剂密封。试验过程中,试件的升温幅度由温度传感器控制,试件的变形用内埋式混凝土应变计和外设千分表测定,温度应力用荷载传感器测定。
对混凝土试件升温较传统的做法是使用水浴或油浴进行加热,在试验中自行设计了电热带加热方案及相应的保温措施,使得给混凝土试件提供较为均匀的温度荷载时,还可以方便地使用约束装置以满足相关条件的模拟。结果表明:
(1)自行设计的电热带加热方案能够给混凝土试件施加较为均匀的温度荷载,升温幅度可达70℃;
(2)在固端约束及弹性约束状态下,温度应力与温度变化之间具有良好的线性关系,混凝土应变计的应变变化与温度应力之间也存在良好的线性关系,但温度应力的实测值远小于理论值。
(3)在约束程度较强,温度场均匀变化时,使用混凝土应变计测定温度应力可以取得较理想的效果。
Through the concrete strain gauges and other observation instruments to monitor the stress state of the structure , has been an important tool to study the work state of the complex structure and verify the correctness of the calculation results , but also an primary method of the early warning and forecasting of the important project. However, the method of thermal stress analysis based on observations of the concrete gauges has not been resolved, so that a large number of observational data cannot be analyze reasonably ,and the observing instruments cannot play their due role in the online monitoring and early warning forecasting. The main purpose of this paper is to analyze the thermal stress based on the measured data of the concrete strain gauge preliminarily.
The thermal stress of the concrete specimen with fixed and elastic restraints at both ends was measured by applying the temperature load on the specimen with an electric heater cable .The concrete specimen is a cylinder with 370mm in height and 105mm in diameter and fixed by the load distribution plates of the testing machine, a vibrating wire strain gauge and a temperature sensor were buried in the center of the specimen, the electric heater cable was wrapped on the lateral surface of the specimen, which was sealed with a layer of polyurethane foam with excellent heat insulating property. In the process of the experiments, the temperature rise was controlled by the temperature sensor, the thermal deformation of the specimen was measured by both embedded vibrating wire strain gauge and the dial gauges installed on the test machine, and the thermal stress was detected by the load sensor.
The concrete specimens are heated in water or oil traditionally; In the test a heating cable program and an insulation system are designed, Which provide a more uniform temperature load and the easily use of restraint setup to meet the conditions of the simulation for concrete specimens.
The results showed that:
(1) The heating cable heating program designed can supply an uniform temperature load to the concrete specimens , a 70℃of the temperatures rise can be reached;
(2) In the state of ends restraint, the thermal stress produced in the specimen is linearly dependent on the temperature rising, and the strain changes measured by the strain gauge is also linearly correlate to the thermal stress, but the measured values of the thermal stress are much smaller than theoretical ones.
(3) In the state of ends restraint strongly and the temperature field changes uniformly, approximate results can be obtained by using the concrete strain gauge to measure the thermal stress.
引文
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[29] Kolver K. Testing system for determining the mechanical behavior of early ages concrete under restrained and free uniaxial shrinkage. Materials and Structure,1994,27(7):324-330.
[30] Altoubat S A, Lange D A. Lange, shrinkage and cracking of restrained concrete at early age. ACI Materials Journal,2001,98(4):323-331
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[37] Muhammad Nasir Amin, Jeong-Su Kim, Yun Lee, Jin-Keun Kim, Simulation of the thermal stress in mass concrete using a thermal stress measuring device [J]. Cement and Concrete Research, 2009, 39: 154-164.
[38]胡曙光,陈静,周志锋.约束可调式单轴温度-应力试验机控制系统设计[J].武汉理工大学学报,2007,29(1)55-57,61.
[39]林志海.混凝土早期开裂试验评价研究[D].北京:清华大学土木工程系建筑材料研究所, 2002.
[40]李士伟,李超,王迎飞.基于温度应力试验机的混凝土控裂技术研究现状[J].水运工程,2010,10:35-39.
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[2]余成行,刘刚,徐有邻.大体积混凝土温度及应变测量分析,混凝土,2007( 2).
[3]麦家煊,孙立勋.西北口堆石坝裂缝成因的研究[J].水利水电技术,1999,30 (5):30—34.
[4]蒋国澄,傅志安,凤家骥.混凝土面板坝工程[M].武汉:湖北科学技术出版社, 1997.
[5]朱伯芳,王同生.水工混凝土结构的温度应力与温度控制[M].北京:水利电力出版社,1976.
[6] Li Shouyi,Zhang Jinkai,Wang Ting. Effect of pouring temperature on temperature stress of RCC gravity dam[C].2008 Fourth International Conference on Natural Computation(ICNC). Jinan, IEEE, 2008(2):355―359.
[7]程嵩,张嘎,张建民,侯文峻.有挤压墙面板堆石坝的面板温度应力分析及改善措施研究[J].工程力学,2011(4).
[8]郑木莲.多孔混凝土排水基层研究[D].西安:长安大学特殊地区公路工程教育部重点实验室,2004.
[9]锁利军.多孔混凝土基层沥青路面结构设计方法研究[D].西安:长安大学特殊地区公路工程教育部重点实验室,2005.
[10]锁利军,王秉纲,郑传超.多孔混凝土基层缩缝处沥青面层温度应力分析[J].武汉理工大学学报(交通科学与工程版),2011(6).
[11]刘振宇,陈宝春.钢管混凝土桁拱热脱粘及温度应力分析[J].公路交通科技,2011(7).
[12]涂光亚,颜东煌,邵旭东.脱黏对桁架式钢管混凝土拱桥受力性能的影响[J].中国公路学报,2007,20(6):61-66.
[13]何雄君,文武松,胡志坚.钢管混凝土拱桥温度荷载分析[J].桥梁建设,2000(1):17-19.
[14]任宪骏,张波,宋怡.汽轮发电机基座底板施工期温度应力分析[J].武汉大学学报(工学版)(增刊),2010(8).
[15]王森荣,孙立,李秋义,吴有松.无砟轨道轨道板温度测量与温度应力分析[J].铁道工程学报,2009(2).
[16]吴家龙.弹性力学[M].北京:高等教育出版社,2001
[17]朱伯芳.有限单元法原理与应用(第三版)[M].北京:中国水利水电出版社:知识产权出版社,2009.
[18]朱伯芳.混凝土坝计算技术与安全评估展望[J].水利水电技术,2006.
[19]朱永全.北京地铁矿山法区间隧道设计方法研究[R].石家庄:石家庄铁道学院, 2006
[20]李文江,朱永全,刘志春.运营期间地铁隧道衬砌结构纵向温度应力分析[J],中国铁道科学,2009
[21]盘少川,刘耀乙,千毫升.实验应力分析[M].上海:高等教育出版社,1989.3
[22]陆采荣,吴胜心.大坝混凝土早期热、力学特征及开裂机理[M].郑州:黄河水利出版社,2010.12
[23]林志海,覃维祖,张士海等.虚拟仪器技术在检测混凝土早期开裂灵敏度试验中的应用.工业建筑,2003,33(7):37-40.
[24] Springenschmid R. Prevention of Thermal Cracking in Concrete at Early Ages. Taylor &Francis,1998.
[25] R. Springenschmid, R. Breitenbucher, M. Mangold. Development of the cracking frame and the temperature-stress testing machine, Proceedings of the International RILEM Symposium: Thermal Cracking in Concrete at Early Ages, E&FN Spon, 1994, pp. 137–144.
[26] Bloom R, Bentur A. Free and restrained shrinkage of normal and high-strength Concrete. ACI Materials Journal,1995,92(2):211-217
[27] Shin-Ichi I, Arnon B, Konstantin K. Autogenous shrinkage and included restraining stresses in high-strength concretes. Cement and Concrete Research,2000,30(11):1701-1707.
[28] Amon B, Shin-Ichi I, Konstantin K. Prevention of autogenous shrinkage in high-strength concrete by internal curing using wet lightweight aggregates. Cement and Concrete Research,2001,31(11):1587-1591
[29] Kolver K. Testing system for determining the mechanical behavior of early ages concrete under restrained and free uniaxial shrinkage. Materials and Structure,1994,27(7):324-330.
[30] Altoubat S A, Lange D A. Lange, shrinkage and cracking of restrained concrete at early age. ACI Materials Journal,2001,98(4):323-331
[31] Penev D, Kawamura M. A laboratory device for restrained shrinkage fracture of soil-cement mixture. Materials and Structure,1992,25(146):115-120
[32]张士海,覃维祖,张涛等.混凝土早期开裂性能评价-单轴约束试验方法的进展[J].混凝土与水泥制品,2002,125(3):13-16.
[33] G. Thielen, W. Hintzen. Investigation of concrete behavior under restraint with a temperature-stress test machine [J]. Proceedings of the International RILEM Symposium: Thermal Cracking in Concrete at Early Ages, E&FN Spon, 1994, pp. 145– 152.
[34] K. Schoppel, M. Plannerer, R. Springenschmid. Determination of restraint stresses and of material properties during hydration of concrete with the temperature– stress testing machine, Proceedings of the International RILEM Symposium: Thermal Cracking in Concrete at Early Ages, E&FN Spon, 1994, pp. 153–160.
[35] R. Breitenbucher. Investigation of thermal cracking with the cracking frame [J]. Materials and Structures, 1990, 23: 172– 177.
[36] Kim, Jang-Ho Jay Jeon, Sang-Eun; Kim, Jin-Keun. Development of new device for measuring thermal stresses [J]. Cement and Concrete Research, 2002, 32 (10): 1645-1651.
[37] Muhammad Nasir Amin, Jeong-Su Kim, Yun Lee, Jin-Keun Kim, Simulation of the thermal stress in mass concrete using a thermal stress measuring device [J]. Cement and Concrete Research, 2009, 39: 154-164.
[38]胡曙光,陈静,周志锋.约束可调式单轴温度-应力试验机控制系统设计[J].武汉理工大学学报,2007,29(1)55-57,61.
[39]林志海.混凝土早期开裂试验评价研究[D].北京:清华大学土木工程系建筑材料研究所, 2002.
[40]李士伟,李超,王迎飞.基于温度应力试验机的混凝土控裂技术研究现状[J].水运工程,2010,10:35-39.
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