scholarly journals Temperature Control Measures and Temperature Stress of Mass Concrete during Construction Period in High-Altitude Regions

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Zhenhong Wang ◽  
Li Tao ◽  
Yi Liu ◽  
Jiang Yunhui
Keyword(s):  
High Altitude ◽  
Temperature Stress ◽  
Temperature Control ◽  
Lower Layer ◽  
Temperature Drop ◽  
Control Measures ◽  
Mass Concrete ◽  
Prevention Measures ◽  
Concrete Gravity Dam ◽  
Climate Conditions

The focus on the development of China’s vast hydropower resources has shifted to Tibet and other plateau regions. These areas are high-altitude regions whose basic climatic characteristics are as follows: dry climate, significant differences in daily temperature, and strong solar radiation. If a dam is built under such special climate conditions, specific and strict temperature control and crack prevention measures should be taken. Therefore, this study explores the temperature control standards, as well as temperature control and crack prevention measures, for concrete in high-altitude regions using three-dimensional finite element methods and based on the concrete gravity dam in Tibet in combination with the characteristics of material properties that are disadvantageous to temperature control and crack prevention. The temperature drop process can be optimized in time, and the temperature drop rate can be controlled to prevent excessive scale and temperature drop rates. Moreover, the temperature gradient can be spatially optimized, and thus, the differences in foundation temperatures, upper- and lower-layer temperatures, and internal and external temperatures can also be reduced. The research shows that the recommended temperature control and crack prevention measures can effectively reduce temperature stress. This study has a significant value as a reference for similar projects in high-altitude regions.

A New Method for Improving the Stress Status of the Dam

2013 ◽  
Vol 444-445 ◽  
pp. 849-853
Author(s):  
Jian Hua Cui ◽  
Yong Feng Qi ◽  
Jie Su
Keyword(s):  
Temperature Control ◽  
Cooling Water ◽  
Control Measures ◽  
Sensitivity Analyses ◽  
Mass Concrete ◽  
Water Cooling ◽  
Concrete Gravity Dam ◽  
3D Fem ◽  
Construction Period ◽  
Operation Period

Under the action of annual change and sudden drop of air temperature, thermal induced cracking will occur in concrete dam during the operation period. For exploring the temperature control measures for crack prevention, taking a concrete gravity dam section as the research object, sensitivity analyses to the factors which affecting the water-cooling effect are conducted with 3D FEM, some significant suggestions for the water cooling are presented. The results show that, the stresses of the dam surface will decrease to a certain extent after water cooling in the operation period using the cooling water pipe which embedded during construction period, and the cracking risk of the dam will reduce. The study provides a new train of thought for the temperature control and crack prevention of the mass concrete during the operation period.

scholarly journals Temperature-stress coupling mechanism analysis of one-time pouring mass concrete

2019 ◽  
Vol 23 (3 Part A) ◽  
pp. 1615-1621 ◽  
Author(s):  
Ben-Gao Yang ◽  
Peng He ◽  
Gao-You Peng ◽  
Tong Lu
Keyword(s):  
Stress Field ◽  
Temperature Stress ◽  
Temperature Control ◽  
Damage Control ◽  
Control Measures ◽  
Effect Of Temperature ◽  
Actual Condition ◽  
Coupling Mechanism ◽  
Mass Concrete ◽  
Finite Element Software

Thermal damage control of mass concrete is the key to guarantee the quality of mass projects. Based on several engineering experiences and finite element software ANSYS, the temperature field and stress field of the typical dam section of the Tengzigou hydropower station in Sichuan province were simulated. Considering the actual materials used, cooling measures, etc., maximum tensile stress and compressive stress at different time points derived from the temperature stress field during the time of concrete maintenance were calculated, and the numerical results showed that strength increment under the given conditions was much less than the actual condition. After the concrete of the dam body of the hydro power station were poured, there was no significant temperature stress crack appeared through a long-term observation, and the project condition was in tune with the calculated expectation. The above research results are valuable to further prediction of concrete temperature in different periods, the pre-study of the effect of temperature control measures, and these could offer guidance of the adjustment of temperature control measures in the case of abnormal conditions.

Study on Crack Prevention Measures of Mass RCC Dams

2013 ◽  
Vol 743 ◽  
pp. 3-8
Author(s):  
Jian Guo Jing ◽  
Min Zhi Liu ◽  
Shao Jun Zeng ◽  
Lin Xu
Keyword(s):  
Temperature Control ◽  
Control Measures ◽  
Simple Construction ◽  
Prevention Measures ◽  
Construction Period ◽  
The Way

Actually, both simple construction and fast construction are advantages of RCC dams. In view of taking strict temperature control measures, those are turned to be disadvantages instead. The way of fast pouring and the measure of controlling the placing temperature are introduced to RCC dams and 6 cases are analyzed separately to explain the effect of their crack prevention. It is concluded that controlling only the last layer placing temperature of concrete lifts can remarkably decrease the stress of working plane concrete during off period. Furthermore, the pouring way of thick lifts and short off period do not deteriorate the temperature and stress but rather has an impressive effect on crack prevention and construction period contraction.

Temperature Control Measures Optimization of RCC Gravity Dam

2012 ◽  
Vol 226-228 ◽  
pp. 1153-1156 ◽  
Author(s):  
Shu Ping Huang ◽  
Jian Yun Fu ◽  
Yan Cai Li
Keyword(s):  
Temperature Control ◽  
Simulation Analysis ◽  
Control Measure ◽  
Control Measures ◽  
Gravity Dam ◽  
Mass Concrete ◽  
Dam Construction ◽  
Construction Technology ◽  
3D Fem ◽  
Single Temperature

With the continuous development of dam construction technology, the RCC dam becomes one of the most popular types of dam in the world with its unique advantages. Temperature control measures research is one of the key issues of design and construction of mass concrete structures. How to choose the proper temperature control measures to prevent concrete cracks becomes the important problem of dam construction technology. In a RCC gravity dam, the climate environment is so severe that a single temperature control measure can’t meet the requirements of temperature control and crack prevention. In this paper, 3D FEM simulation analysis is used to calculate temperature field and thermal creep stress field during the whole construction process. According to the simulation results, the temperature control measures design of the dam has been comprehensively evaluated and the temperature control measures of this project have been put forward.

scholarly journals Study on Optimization of Temperature Control Measures for Structure Concrete of Arc Dam

2021 ◽  
Author(s):  
Lei Zhang ◽  
Xiaofang Ma ◽  
Heng Zhao ◽  
Lei Zheng ◽  
Shouxun Ma
Keyword(s):  
Phase I ◽  
Temperature Stress ◽  
Temperature Control ◽  
Simulation Analysis ◽  
Complex Structure ◽  
Arch Dam ◽  
Control Measures ◽  
3D Fem ◽  
Water Pipes ◽  
Cooling Temperature

As the gate pier bracket of an arch dam are of complex structure which is characterized by use of high-grade concrete and more cement, higher adiabatic temperature rise, it is rather difficult to control temperature and vulnerable for cracking, and the cracks would absolutely affect the integrity, endurance and safety of pier gate bracket. It is necessary to take reasonable temperature control measures to reduce temperature stress during the construction and prevent cracking. This paper takes the gate pier bracket at the middle-hole dam section to perform simulation analysis of temperature field and stress field under different temperature control measures by 3D FEM. It proves that such measures as densifying water pipes, improving Phase I target cooling temperature appropriately, reducing Phase I cooling temperature falling variation and keeping insulation in low-temperature season can help reduce temperature stress and prevent cracking with good results.

Temperature Cracks Controlling Technology for the Mass Concrete in Solid Sections of Lower Pylon Column

2013 ◽  
Vol 467 ◽  
pp. 262-269
Author(s):  
Fu Liang Gao ◽  
Yan Wei Fang
Keyword(s):  
Temperature Control ◽  
Thermal Stresses ◽  
Cooling Water ◽  
Control Measures ◽  
Mass Concrete ◽  
Removal Time ◽  
Control Scheme ◽  
Section Size ◽  
Circulating Cooling Water ◽  
Binder Ratio

According to the case that mass concrete in solid sections of lower pylon column of Jiashao Bridge was easy to crack in construction because of the bigger section size, larger content of cementitious material and lower water binder ratio, the temperature and thermal stresses distribution of mass concrete was simulated and temperature control scheme was adjusted constantly based on the results of field temperature monitoring. Through taking some temperature control measures such as applying circulating cooling water and prolonging the time appropriately, thermal insulation and moisture retention curing, extending the form removal time and controlling the quality of concrete, harmful cracks did not appear in solid sections of lower pylon column of Jiashao Bridge and anticipated temperature control requirements were achieved.

Cracking Risk Analysis of Concrete Dam at Early Age under Concrete Fast Pouring Method

2014 ◽  
Vol 638-640 ◽  
pp. 735-739
Author(s):  
Hai Bo Wang
Keyword(s):  
Temperature Control ◽  
Point Of View ◽  
Control Measures ◽  
Early Age ◽  
Concrete Gravity Dam ◽  
Time Intervals ◽  
Concrete Dam ◽  
Control Criteria ◽  
Short Time ◽  
Cracking Risk

In order to speed up the progress of the concrete dam construction, the concrete thick layers and short time intervals fast pouring method is proposed. The temperature cracking and stress safety of the dam under concrete fast pouring method is a big trouble. From the concrete cracking safety point of view, a concrete gravity dam is introduced as a case study, the influence of different thickness of layers, different time intervals and different pouring temperature on the temperature and thermal stress characteristics of the concrete dam at the early age as well as the cracking risk of the concrete are deeply studied. According to the analysis, the corresponding cracking prevention technology is put forward. The research provides a technical support for establishing the concrete temperature control criteria and the relevant temperature control measures for the concrete fast pouring method.

Temperature Control Measures' Intelligent Optimization for Quasi-Mass Concrete Structure

2013 ◽  
Vol 357-360 ◽  
pp. 884-887
Author(s):  
Yao Ying Huang ◽  
Yue Mei Ding ◽  
Xiao Man Lv ◽  
Teng Fei Tang
Keyword(s):  
Neural Network ◽  
Temperature Control ◽  
Growth Curve ◽  
Control Measures ◽  
Tension Stress ◽  
Mass Concrete ◽  
Water Cooling ◽  
Optimal Temperature ◽  
Tension Strength ◽  
Temperature Water

Related to temperature control measures and material parameters, crack prevention by temperature control in quasi-mass concrete is an optimization problem including multiple complicated factors. This study tries to do some optimization of temperature control measures in the given concrete thermodynamics parameters circumstance. The quasi-mass concrete structure’s minimum value of the relationship between principal tensile stress duration curves of internal and surface and the tensile strength growth curve are taken as the input, and the gate pier surface heat preservation effect, pouring temperature, water cooling temperature, water cooling time are taken as the output, we establish the optimal temperature control measures by the neural network model. Applying the uniform design principle to combine the temperature control parameters, and using the finite element method to analyze the temperature field and creep stress field in the quasi-mass concrete structure containing cooling water pipes, we obtain the samples, for training the network, to describe the nonlinear relationship between the principal tension stress duration curve and the tension strength growth curve and the different temperature control measures. After inputting the fitting minimum value of relationship between the principal tension stress duration curve and the tension strength growth curve to the trained network, the system is able to automatically select the optimal temperature control measures for crack prevention. The example shows that the proposed optimal neural network model for temperature control measures is feasible.

Influence of Water Pipe Cooling on Thermal Stresses in Mass Concrete

2011 ◽  
Vol 137 ◽  
pp. 12-15
Author(s):  
Xin Li Bai ◽  
Ze Yu Wu ◽  
Wen Liang Ma ◽  
Dan Fei Wang
Keyword(s):  
Temperature Control ◽  
Thermal Stresses ◽  
Early Period ◽  
Control Measures ◽  
Mass Concrete ◽  
Late Period ◽  
Water Pipe ◽  
Effective Measure ◽  
Influence Of Water ◽  
Water Pipe Cooling

Temperature field and stress field of a concrete slab in a ship lock chamber are calculated, considering the influence of layered casting. And the influence of water pipe cooling at the early period of constructing, and at the period after constructing, sunshade, pre-cooled concrete etc are taken into account. The expression of finite difference method considering the effect of water pipe cooling is deducted for temperature analysis. Thermal stress calculation results show that the water pipe cooling at the mid-late period is a comparatively effective measure to reduce tensile stress of chamber mass concrete. And an effective temperature control measure is recommended in summer casting, which is that: sunshade + pre-cooled concrete + water pipe cooling (both at early period and at mid-late period). Mid-late period water pipe cooling must last for three months. Combined with other temperature control measures such as summer cover maintenance, winter cover preservation etc, the concrete cracks can be reduced, and the occurrence of large area run through cracks can be avoided.

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