[周先雁] College of Civil Engineering, Architecture and Mechanics, Central South University of Forestry and Technology, Changsha 410004, China;[曹國輝] Civil Engineering College, Hunan City University, Yiyang 413000, China
College of Civil Engineering, Architecture and Mechanics, Central South University of Forestry and Technology, China
[Liu, Xiao-Fang; Cao, Guo-Hui; Liu, Xiang-Rong; He, Ran] Hunan City Univ, Sch Civil Engn, Yiyang 413000, Peoples R China.
4th International Symposium on Lifetime Engineering of Civil Infrastructure
OCT 26-28, 2009
Changsha, PEOPLES R CHINA
[Cao, Guo-Hui;He, Ran;Liu, Xiao-Fang;Liu, Xiang-Rong] Hunan City Univ, Sch Civil Engn, Yiyang 413000, Peoples R China.
Concrete columns;creep;ultimate strength
Long-term mechanical properties test for 864 days were completed on three types column, including plain concrete(PC), reinforced concrete(RC) and concrete-filled steel tube(CFST) columns, the creep performance and ultimate strength were tested and analyzed. Creep test results show that reinforcement can significantly reduce the creep deformation of concrete columns. The creep coefficient of steel pipe surface is larger than that of inner concrete for CFST columns, it would last a long time for the creep of inner concrete to achieve stability. The ultimate strength test results show that loading age and reinforcement have great effect on extreme compression strain and ultimate strength of PC columns and RC columns. Whether it has loading course would influence the stress redistribution of CFST columns, the stress redistribution effect is relatively small for columns having loading course. However, whether it has loading course, the creep effect on the ultimate strength of CFST columns is very small.
Journal of Central South University,2016年23(2):470-478 ISSN：2095-2899
[Cao Guo-hui; Zhang Kai] Hunan City Univ, Coll Civil Engn, Yiyang 413000, Peoples R China.;[Hu Jia-xing] Hunan Univ, Coll Civil Engn, Changsha 410082, Peoples R China.
College of Civil Engineering, Hunan City University, Yiyang, China
prestress;relaxation loss;shrinkage and creep;theoretical analysis;calculation model
The calculation model for the relaxation loss of concrete mentioned in the Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts (JTG D62—2004) was modified according to experimental data. Time-varying relaxation loss was considered in the new model. Moreover, prestressed reinforcement with varying lengths (caused by the shrinkage and creep of concrete) might influence the final values and the time-varying function of the forecast relaxation loss. Hence, the effects of concrete shrinkage and creep were considered when calculating prestress loss, which reflected the coupling relation between these effects and relaxation loss in concrete. Hence, the forecast relaxation loss of prestressed reinforcement under the effects of different initial stress levels at any time point can be calculated using the modified model. To simplify the calculation, the integral expression of the model can be changed into an algebraic equation. The accuracy of the result is related to the division of the periods within the ending time of deriving the final value of the relaxation loss of prestressed reinforcement. When the time division is reasonable, result accuracy is high. The modified model works excellently according to the comparison of the test results. The calculation result of the modified model mainly reflects the prestress loss values of prestressed reinforcement at each time point, which confirms that adopting the finding in practical applications is reasonable.
[張鍇; 曹國輝] School of Civil Engineering, Hunan City University, Yiyang, China;[胡佳星] School of Civil Engineering, Hunan University, Changsha, China;[張勝; 張旺] School of Civil Engineering and Architecture, Changsha University of Science &, Technology, Changsha, China
School of Civil Engineering, Hunan City University, Yiyang, China