| With the rapid development of China's economy and science and technology,it is constantly catching up with the technological level of developed countries,and concrete has been widely used and invested.In the past two hundred years,the use of concrete in engineering has added a large number of reliable buildings to this world.While using concrete,it also has a lot of technical difficulties.The research on the temperature control and crack prevention of concrete has always been a problem for researchers in various countries.Through continuous exploration,great progress and development have been made.However,in China's water conservancy projects,the phenomenon of concrete cracking in major dams and other infrastructure projects has become the most important issue in current construction and scientific research.Whether the concrete itself can be reliably operated in its entire life cycle,to ensure that it meets the design requirements and use requirements,and to ensure that the main body of the structure will not crack is still the main problem when using concrete.Therefore,the research on concrete cracking and various aspects has become the most important development direction in China in the field of concrete.Among the causes of cracks,the temperature-controlled stress effect of concrete is the main reason for the early cracking of concrete.Concrete has a reaction of hydration heat inside the initial setting stage.As the level of concrete is higher,the hydration heat phenomenon is more serious,generally After pouring the concrete in the mold,measures such as regular watering and curing should be taken.Otherwise,the large temperature difference between inside and outside will cause uneven shrinkage of the inside and outside concrete and cracks.Paihekou Pumping Station is located at the beginning of the Jianghuai-Huaihua section and is an important hub connecting the Yangtze River and the Huaihe River,especially when it is poured in the hot summer,so temperature control construction is required.This article comprehensively introduces the concrete temperature control scheme which is mainly based on water cooling and reducing concrete pouring temperature,transportation and insulation,strict control of material selection,and surface maintenance of concrete.The finite element analysis software Midas / civil was used to numerically simulate the different cooling water pipe layout interval parameters of theconcrete body poured by the Paihekou pumping station.The distribution law and change of internal and external temperature field of volume concrete,in order to predict the problems in concrete construction in advance,can effectively control the occurrence of harmful cracks.By comparing and analyzing the simulation results with the actual monitoring data of the project,the conclusion is as follows:(1)Using MIDAS-CIVIL software to simulate the temperature field of the same condensate pipe arrangement as the actual project,it can be found that the change trend of the obtained temperature curve is in good agreement with the actual engineering monitoring data.In line with engineering simulation requirements,you can refer to finite element model analysis data to guide engineering practice.(2)Laterally compare the on-site temperature monitoring data of the flow channel and combine with the actual working conditions,pointing out that the reason why the short edge of the structure is inconsistent with the numerical simulation results is that the water inlet and the water outlet are set at the same end of the structure,even if the water flow direction is changed every 24 hours,Can not produce a cooling effect on the remote structural parts.Therefore,when the cooling water pipes are arranged in the structure,it is necessary to ensure that the water outlet and the water inlet are not at the same end of the structure.(3)Comparing the core temperature measured at the long edge of the structure and the short edge of the structure,the highest temperature value reached is different,and the temperature value of the short edge of the structure is significantly higher than the long edge.According to simulation analysis and calculation,the closer the cooling water pipes are arranged,the greater the difference.Therefore,the temperature control scheme for water cooling in concrete structures with a large aspect ratio should be strictly controlled according to the characteristics of the project,and the horizontal spacing of the cooling water pipes should be strictly controlled.(4)The on-site temperature monitoring data shows that after the pouring of the flow channel concrete,the temperature of the concrete core is ?65 ?,and after the initial setting of the concrete,the maximum internal and external temperature difference is ?20 ?,which meets the temperature control requirements.(5)After the completion of the flow channel concrete of the Paihekou Pumping Station,no temperature cracks were found on the surface of the flow channel structure,indicating that the temperature control of the flow channel was successful,and it can provide reference value for other subsequent large-volume concrete projects.Figure [32] table [17] reference [56]... |
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