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.

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.

Study on Thermal Stress and Temperature Cracks Control of Longlin Roller Compacted Concrete Gravity Dam

2012 ◽  
Vol 212-213 ◽  
pp. 912-916 ◽  
Author(s):  
Wen Yi Zheng ◽  
Peng Pan ◽  
Lie Ping Ye
Keyword(s):  
Temperature Control ◽  
Simulation Analysis ◽  
Control Function ◽  
Heat Of Hydration ◽  
Control Measures ◽  
Gravity Dam ◽  
Concrete Gravity Dam ◽  
Progress Control ◽  
Roller Compacted Concrete ◽  
Rational Construction

In order to guide temperature control design and construction and to guarantee the construction quality of roller compacted concrete (RCC) gravity dams in severe cold area, it is of great significance to carry out the simulation analysis of temperature and stress. The whole progress of construction and operation of Longlin RCC gravity dam in harsh climate region were simulated by using the heat of hydration analysis control function, construction stag analysis control function and the time-dependent material link of MIDAS.civil.2006. According to the construction process, the curves of temperature and the curves of stress were obtained. The locations where the crack ratio may exceed 20 were also obtained and the correct temperature control measures and the rational construction progress control system were pointed out.

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.

Simulation Analysis of Plain Sluice Concrete Temperature and Stress

2013 ◽  
Vol 438-439 ◽  
pp. 583-587
Author(s):  
Kai Yun Yang ◽  
Fei Guo ◽  
Lin Hao Li
Keyword(s):  
Temperature Control ◽  
Concrete Structure ◽  
Simulation Analysis ◽  
Model Simulation ◽  
Element Model ◽  
Control Measures ◽  
Construction Period ◽  
Windy Weather ◽  
Cracking Risk ◽  
The Finite Element Model

For sluice concrete structure is more complex due to constrained by the base effect and upper structures, with the purpose of temperature control, we carry out the simulation analysis of temperature and stress during the construction of pier concrete structure. Taking a sluice project as an example, use the method developed by Thermo finite subspace model simulation procedures, the finite element model of pier structure is built with high precision. The results show that the cracking risk is relatively small and prone to surface cracks for baseplate; during construction period, much more attention should be payed to the high temperature difference between day and night, and to the insulation work at cold and windy weather; the key problem is that the middle pier which faces relatively great cracking risk, and necessary temperature control measures should be adopted.

Proposal of PV Output Estimate Method in Short Time Intervals

2016 ◽  
Vol 136 (12) ◽  
pp. 891-897 ◽  
Author(s):  
Katsuhiro Matsuda ◽  
Kazuhiro Misawa ◽  
Hirotaka Takahashi ◽  
Kenta Furukawa ◽  
Satoshi Uemura
Keyword(s):  
Time Intervals ◽  
Estimate Method ◽  
Short Time

EVALUATION OF SHORT TIME INTERVALS IN NORMAL AGING AND LATE-LIFE DEPRESSIONS

2020 ◽  
pp. 54-69
Author(s):  
Elena Yu. Balashova ◽  
◽  
Lika I. Mikeladze ◽  
Elena K. Kozlova ◽  
◽  
...  
Keyword(s):  
Late Life ◽  
Normal Aging ◽  
Time Intervals ◽  
Short Time

Radar-aided CSO-control-criteria for an ecological approach

1997 ◽  
Vol 36 (8-9) ◽  
pp. 223-228
Author(s):  
A. Petruck ◽  
F. Sperling
Keyword(s):  
Critical Time ◽  
Integrated Approach ◽  
Control Measures ◽  
Real Time Control ◽  
Sewer System ◽  
Time Control ◽  
Physical Measurements ◽  
Combined Sewer ◽  
Receiving Stream ◽  
Control Criteria

The control strategy of a combined sewer system incorporating three stormwater storage tanks with overflows presented here attempts to consider all aspects of acute CSO effects. These are the hydraulic and the composition components as well as the time factor. The result is an integrated approach, which is not based on the classic emission view (i.e. reduction of volume), but on pollution criteria (i.e. possible harm to the biotic community). The aim is to reduce the exceeding of critical peak values of the CSO components at critical time intervals. Control decisions will be based on continuous measurements in the sewer system and in the receiving stream. Furthermore the measurements are carried out to determine the effects (both hydraulic and chemical) of particular CSO discharges in order to evolve the critical values for the project area. The chemical and physical measurements are accompanied by a biological monitoring programme. Macroinvertebrates are sampled upstream and downstream of outfalls and at a reference site. This allows the evaluation of the control measures on an ecological basis, and thus an assessment of the ecological potential of radar-aided real-time control of the combined sewer systems.

scholarly journals Neural Network Approach for Global Solar Irradiance Prediction at Extremely Short-Time-Intervals Using Particle Swarm Optimization Algorithm

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1213
Author(s):  
Ahmed Aljanad ◽  
Nadia M. L. Tan ◽  
Vassilios G. Agelidis ◽  
Hussain Shareef
Keyword(s):  
Neural Networks ◽  
Particle Swarm Optimization ◽  
Solar Irradiance ◽  
Particle Swarm ◽  
Time Interval ◽  
Time Intervals ◽  
Swarm Optimization ◽  
Backpropagation Neural Networks ◽  
Proposed Model ◽  
Short Time

Hourly global solar irradiance (GSR) data are required for sizing, planning, and modeling of solar photovoltaic farms. However, operating and controlling such farms exposed to varying environmental conditions, such as fast passing clouds, necessitates GSR data to be available for very short time intervals. Classical backpropagation neural networks do not perform satisfactorily when predicting parameters within short intervals. This paper proposes a hybrid backpropagation neural networks based on particle swarm optimization. The particle swarm algorithm is used as an optimization algorithm within the backpropagation neural networks to optimize the number of hidden layers and neurons used and its learning rate. The proposed model can be used as a reliable model in predicting changes in the solar irradiance during short time interval in tropical regions such as Malaysia and other regions. Actual global solar irradiance data of 5-s and 1-min intervals, recorded by weather stations, are applied to train and test the proposed algorithm. Moreover, to ensure the adaptability and robustness of the proposed technique, two different cases are evaluated using 1-day and 3-days profiles, for two different time intervals of 1-min and 5-s each. A set of statistical error indices have been introduced to evaluate the performance of the proposed algorithm. From the results obtained, the 3-days profile’s performance evaluation of the BPNN-PSO are 1.7078 of RMSE, 0.7537 of MAE, 0.0292 of MSE, and 31.4348 of MAPE (%), at 5-s time interval, where the obtained results of 1-min interval are 0.6566 of RMSE, 0.2754 of MAE, 0.0043 of MSE, and 1.4732 of MAPE (%). The results revealed that proposed model outperformed the standalone backpropagation neural networks method in predicting global solar irradiance values for extremely short-time intervals. In addition to that, the proposed model exhibited high level of predictability compared to other existing models.

Simulation of thermal stress and control measures for rock-filled concrete dam in high-altitude and cold regions

2021 ◽  
Vol 230 ◽  
pp. 111721
Author(s):  
Yuxiang Zhang ◽  
Jianwen Pan ◽  
Xinjian Sun ◽  
Jijun Feng ◽  
Dengqiang Sheng ◽  
...  
Keyword(s):  
Thermal Stress ◽  
High Altitude ◽  
Control Measures ◽  
Concrete Dam ◽  
Cold Regions ◽  
And Control
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