Study On Temperature Effect And Temperature Control Measures Of Prestressed Concrete Groove Beam

In recent years,prestressed concrete groove beam has been widely used due to its advantages such as thin and light bottom plate,beautiful appearance and low building height.The groove beam is a thin-walled concrete structure.Because of its small cross-sectional dimension and low peak temperature of hydration heat,people often ignore the influence of temperature effect during design and construction,and believe that it does not cause cracks.In fact,there have been many cases showing that thin-walled concrete structures also produce temperature cracks,so it is necessary to explore the influence of temperature effect on the groove beams.This paper takes a Ningbo expressway project as the background,chooses the representative 35 m concrete groove beam as the research object,based on the measured data,analyzes its temperature effect by using ANSYS.The main contents of this paper are as follows:(1)Tracking and monitoring the hydration heat and sunshine temperature field of the groove beam.Through the analysis of the measured temperature data,the development law of the hydration heat and sunshine temperature field of the groove beam is summarized.(2)This paper simulates the hydration heat reaction of the groove beam,and analyzes the hydration heat temperature field and stress field of the groove beam during construction.The results show that the calculated values of the temperature field agree well with the measured values,which proves the reliability of the finite element model;there are large temperature stresses at the groove beam end and flange positions,which should be closely monitored during the construction process;after the optimization of the construction scheme,the maximum temperature stress of the groove beam is reduced by 0.31 MPa,and the hydration heat effect is obviously alleviated.(3)The influence of ambient temperature,wind speed,pouring temperature and cement dosage on the hydration heat of the groove beam is analyzed by the controlvariable method,and the corresponding temperature control measures are discussed.The results show that too low ambient temperature,too high wind speed,too much mold temperature,and excessive amount of cement in unit concrete will make the hydration heat effect of the groove beam develop in an unfavorable direction.Therefore,in the actual project,measures such as covering insulation layer,mixing concrete with cold water,pouring concrete at night,and adding fly ash should be adopted to reduce the temperature difference between the inside and outside of the concrete to prevent the occurrence of temperature cracks.(4)A more reasonable three-dimensional sunshine model of groove beam is established by ANSYS,and the temperature field and stress field of the groove beam under the action of sunlight are simulated and analyzed.The results show that the groove beam end has a large temperature gradient due to the long exposure time and small angle of sunlight,which produces a large temperature stress.The maximum temperature stress of the groove beam under high temperature conditions in summer reaches 3.08 MPa,which may lead to the occurrence of temperature cracks,which should be paid enough attention.