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.

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 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.

Key Technical Issues and Optimization Analysis on Temperature Control and Crack Prevention Measures for Xiluodu Super-High Arch Dam during the Construction Period

2014 ◽  
Vol 584-586 ◽  
pp. 2043-2051
Author(s):  
You Zhi Liu ◽  
Guo Xin Zhang ◽  
Ping Yang ◽  
Shao Wu Zhou
Keyword(s):  
Simulation Analysis ◽  
Arch Dam ◽  
Control Measures ◽  
Effective Control ◽  
Engineering Practice ◽  
Prevention Measures ◽  
High Arch Dam ◽  
Safety Control ◽  
Construction Period ◽  
Transverse Joint

By utilizing the transverse joint opening and closing iteration technique and the finite element method based on the discontinuous deformation theory for manifolds, and with the help of measured data in situ of temperature, stress and displacement and so on during the construction period, the dynamic tracing feedback simulation/analysis was carried out to the temperature field and the stress field. On this basis, a series of effective safety control measures and methods were systematically put forward, which are beneficial to safety construction in the high temperature season and winter, improvement of the safety coefficient for restrained zones, lowering the cracking risk of low gradation concrete in portholes, ensuring the transverse joints aperture and groutability as well as effective control of the cantilever height and so on; and good effects have been obtained in the engineering practice and the important guarantee may be provided for the overall safety of Xiluodu Super-high arch dam.

Study on Concrete's Temperature Control Measures for Inverted-Siphons during Construction Period

2012 ◽  
Vol 443-444 ◽  
pp. 792-795
Author(s):  
Xiao Mei Dong ◽  
Yi He ◽  
Jing Chao Sun
Keyword(s):  
Temperature Control ◽  
Concrete Surface ◽  
Control Measures ◽  
Good Effect ◽  
Construction Period ◽  
Inverted Siphon ◽  
Time Space ◽  
North Water ◽  
Water Pipe Cooling

In view of the problem of concrete cracks during construction, the good effect of cracks prevention can be achieved if the timely and reasonable scheme of temperature control is selected. Under the 3-D FEM including water-pipe cooling is adopted to simulate the stresses field of Inverted siphon during construction. Through analyzing the time-space variation law, it is fund that cracks easily appear. In the part of the middle line of the South-North Water Transfer Project£¬the quality of concrete surface of III section in Jiaozuo has been improved obviously through the method of external insulation board.

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.

scholarly journals Universal Masking to Control Healthcare-Associated Transmission of SARS-CoV-2

2021 ◽  
pp. 1-24
Author(s):  
Eliza R. Thompson ◽  
Faith S. Williams ◽  
Pat A. Giacin ◽  
Shay Drummond ◽  
Eric Brown ◽  
...  
Keyword(s):  
Large Scale ◽  
Infection Prevention ◽  
Index Patient ◽  
Field Investigation ◽  
Point Prevalence ◽  
Control Measures ◽  
Prevention Measures ◽  
Infection Control Measures ◽  
Va Health Care System ◽  
Healthcare Associated

Abstract Objective: To assess extent of a healthcare-associated outbreak of SARS-CoV-2 and evaluate effectiveness of infection control measures, including universal masking Design: Outbreak investigation including 4 large-scale point-prevalence surveys Setting: Integrated VA Health Care System with 2 facilities and 330 beds Participants: Index patient and 250 exposed patients and staff Methods: We identified exposed patients and staff and classified them as probable and confirmed cases based on symptoms and testing. We performed a field investigation and assessment of patient and staff interactions to develop probable transmission routes. Infection prevention interventions implemented included droplet and contact precautions, employee quarantine, and universal masking with medical and cloth facemasks. Four point-prevalence surveys of patient and staff subsets were conducted using real-time reverse-transcriptase polymerase chain reaction for SARS-CoV-2. Results: Among 250 potentially exposed patients and staff, 14 confirmed cases of Covid-19 were identified. Patient roommates and staff with prolonged patient contact were most likely to be infected. The last potential date of transmission from staff to patient was day 22, the day universal masking was implemented. Subsequent point-prevalence surveys in 126 patients and 234 staff identified 0 patient cases and 5 staff cases of Covid-19, without evidence of healthcare-associated transmission. Conclusions: Universal masking with medical facemasks was effective in preventing further spread of SARS-CoV-2 in our facility in conjunction with other traditional infection prevention measures.

scholarly journals Research on concrete temperature control measures in deep hole area of super high arch dam

2021 ◽  
Vol 826 (1) ◽  
pp. 012035
Author(s):  
Yuchen Fu ◽  
Yaosheng Tan ◽  
Chunfeng Liu ◽  
Lei Pei ◽  
Yajun Wang ◽  
...  
Keyword(s):  
Temperature Control ◽  
Arch Dam ◽  
Control Measures ◽  
Deep Hole ◽  
High Arch Dam ◽  
Hole Area ◽  
Concrete Temperature

scholarly journals The Impact of COVID-19 on Pedestrian Flow Patterns in Urban POIs—An Example from Beijing

2021 ◽  
Vol 10 (7) ◽  
pp. 479
Author(s):  
Yihang Li ◽  
Liyan Xu
Keyword(s):  
Prevention And Control ◽  
Control Period ◽  
Flow Patterns ◽  
Control Measures ◽  
Pedestrian Flow ◽  
Prevention Measures ◽  
Government Control ◽  
Functional Categories ◽  
And Control ◽  
The Impact

The COVID-19 pandemic is a major challenge for society as a whole, and analyzing the impact of the spread of the epidemic and government control measures on the travel patterns of urban residents can provide powerful help for city managers to designate top-level epidemic prevention policies and specific epidemic prevention measures. This study investigates whether it is more appropriate to use groups of POIs with similar pedestrian flow patterns as the unit of study rather than functional categories of POIs. In this study, we analyzed the hour-by-hour pedestrian flow data of key locations in Beijing before, during, and after the strict epidemic prevention and control period, and we found that the pedestrian flow patterns differed greatly in different periods by using a composite clustering index; we interpreted the clustering results from two perspectives: groups of pedestrian flow patterns and functional categories. The results show that depending on the specific stage of epidemic prevention and control, the number of unique pedestrian flow patterns decreased from four before the epidemic to two during the strict control stage and then increased to six during the initial resumption of work. The restrictions on movement are correlated with most of the visitations, and the release of restrictions led to an increase in the variety of unique pedestrian flow patterns compared to that in the pre-restriction period, even though the overall number of visitations decreased, indicating that social restrictions led to differences in the flow patterns of POIs and increased social distance.

Hospital-acquired infection awareness and control practices among healthcare staff: an evaluation

2021 ◽  
Vol 27 (11) ◽  
pp. 296-302
Author(s):  
Pallavi Saraswat ◽  
Rajnarayan R Tiwari ◽  
Muralidhar Varma ◽  
Sameer Phadnis ◽  
Monica Sindhu
Keyword(s):  
Infection Control ◽  
Healthcare Facility ◽  
Hospital Staff ◽  
Control Measures ◽  
Prevention Measures ◽  
Cross Sectional ◽  
Control Policies ◽  
Hospital Acquired Infection ◽  
Hospital Acquired Infections ◽  
Hospital Acquired

Background/Aims Hospital-acquired infections pose a risk to the wellbeing of both patients and staff. They are largely preventable, particularly if hospital staff have adequate knowledge of and adherence to infection control policies. This study aimed to assess the knowledge, awareness and practice of hospital-acquired infection control measures among hospital staff. Methods A cross-sectional study was conducted among 71 staff members in a tertiary healthcare facility in Karnataka, India. The researchers distributed a questionnaire containing 33 questions regarding knowledge of hospital-acquired infections, awareness of infection control policies and adherence to control practices. The results were analysed using the Statistical Package for the Social Sciences, version 16.0 and a Kruskal–Wallis test. Results Respondents' mean percentage score on the knowledge of hospital-acquired infections section was 72%. Their mean percentage scores on the awareness and practice of infection prevention measures sections were 82% and 77% respectively. Doctors and those with more years of experience typically scored higher. Conclusion The respondents had an acceptable level of knowledge, awareness and adherence to infection control practices. However, continued training is essential in the prevention of hospital-acquired infections. The majority of the respondents stated that they were willing to undertake training in this area, and this opportunity should be provided in order to improve infection control quality.

scholarly journals The hygiene hypothesis, the COVID pandemic, and consequences for the human microbiome

2021 ◽  
Vol 118 (6) ◽  
pp. e2010217118
Author(s):  
B. Brett Finlay ◽  
Katherine R. Amato ◽  
Meghan Azad ◽  
Martin J. Blaser ◽  
Thomas C. G. Bosch ◽  
...  
Keyword(s):  
Human Health ◽  
Human Microbiome ◽  
Risk Groups ◽  
Hygiene Hypothesis ◽  
Control Measures ◽  
Prevention Measures ◽  
Long Term Effects ◽  
Substantial Impact ◽  
Future Challenges

The COVID-19 pandemic has the potential to affect the human microbiome in infected and uninfected individuals, having a substantial impact on human health over the long term. This pandemic intersects with a decades-long decline in microbial diversity and ancestral microbes due to hygiene, antibiotics, and urban living (the hygiene hypothesis). High-risk groups succumbing to COVID-19 include those with preexisting conditions, such as diabetes and obesity, which are also associated with microbiome abnormalities. Current pandemic control measures and practices will have broad, uneven, and potentially long-term effects for the human microbiome across the planet, given the implementation of physical separation, extensive hygiene, travel barriers, and other measures that influence overall microbial loss and inability for reinoculation. Although much remains uncertain or unknown about the virus and its consequences, implementing pandemic control practices could significantly affect the microbiome. In this Perspective, we explore many facets of COVID-19−induced societal changes and their possible effects on the microbiome, and discuss current and future challenges regarding the interplay between this pandemic and the microbiome. Recent recognition of the microbiome’s influence on human health makes it critical to consider both how the microbiome, shaped by biosocial processes, affects susceptibility to the coronavirus and, conversely, how COVID-19 disease and prevention measures may affect the microbiome. This knowledge may prove key in prevention and treatment, and long-term biological and social outcomes of this pandemic.

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