Study On Influence Of Environmental Temperature On Thermal Stress Of Super Long Concrete Floor

With the continuous development of construction technology,the application of super long concrete floor in engineering is more and more widely.How to prevent the floor from temperature cracks caused by temperature stress exceeding the tensile strength of concrete has become an urgent problem.The temperature stress is related to the temperature difference of the structure.Only when the temperature difference of the structure is determined,the temperature stress of the structure can be calculated accurately.Structure temperature difference is composed of hydration heat temperature difference,shrinkage equivalent temperature difference and environment temperature difference.The former two kinds of temperature difference have more mature calculation methods,but the research on environment temperature difference,that is,structure affected by environment temperature change,is very scarce.However,in practical engineering,it is found that temperature cracks may appear in the construction stage of super long concrete floor,which indicates that the change of environmental temperature has an important influence on the temperature stress of floor.In this paper,the influence of ambient temperature on the thermal stress of super long concrete floor is studied by experiment and numerical simulation.(1)In the past,when calculating the temperature stress,engineers usually calculate the temperature stress by taking the outdoor environment temperature change as the structure temperature difference,which inevitably overestimates the temperature stress of the structure.Because it is the basement indoor temperature that directly affects the temperature change of the floor,and the basement indoor temperature is affected by the outdoor temperature.It is found that the influence of outdoor temperature on indoor temperature is related to the construction conditions of basement.For example,when the basement roof is poured,the influence of outdoor temperature on indoor temperature becomes smaller.Therefore,based on the investigation and statistics of the basement working time of 32 projects,the corresponding working time values are obtained,including the basement closure time of different areas and the backfill time of basement exterior wall.Combined with the test temperature data,the relationship between the indoor temperature and the outdoor temperature of the basement under different working conditions is obtained,which lays the foundation for using the numerical simulation software to analyze and predict the floor temperature change.Based on the temperature measurement experiments of 8 different thickness floors,the relationship among floor structure temperature,underground indoor temperature and outdoor environment temperature is studied,and the corresponding temperature difference ratio value table is put forward.Based on the study of the variation law of the floor structure temperature,the influence of different conditions(component size,construction method,working condition,pouring season)on the floor temperature variation is obtained.(2)This paper summarizes the mix proportion of several engineering concrete floors,puts forward the reference mix proportion through comparative analysis,and uses the finite element software ANSYS to simulate and analyze the floor temperature,and obtains the temperature change curve of different thickness floor under the condition of test temperature.Because the outdoor environment temperature is constantly changing,it is difficult to predict the floor temperature change in the actual construction process.According to the relationship between indoor temperature and outdoor temperature under different working conditions,and combined with the time value of underground structure working conditions,this paper puts forward the temperature simulation method of super long concrete floor based on Meteorological temperature and working conditions,and verifies the positive effect of this method through an example This method can be used to accurately predict the temperature change of the floor in the construction stage.(3)According to the experimental and numerical simulation data,the composition of temperature difference of super long concrete floor is summarized,and the temperature stress curve of the floor is calculated,and the influence law of environmental temperature on the temperature stress of the floor is obtained.According to the temperature stress in the most unfavorable pouring season,the reasonable partition length of super long concrete floor under different constraint conditions is proposed.In this paper,the variation law of temperature stress of super long concrete floor affected by environmental temperature is analyzed and studied,and the relevant technical measures to reduce the temperature difference of floor structure and control the temperature stress are put forward,which has important guiding significance for the construction of super long concrete floor.