Temperature Effect Analysis And Crack Control Of Super Long Concrete Shear Wall During Construction Period

With the rapid development of China's economy and the continuous progress of Engineering technology,a large number of super-long concrete structures have been widely used in engineering construction.In order to meet the requirements of structural bearing capacity,stiffness,stability,etc.,the wall structure tends to have a long and large size.During the construction process,the concrete hydration produces a large amount of hydration heat,and the concrete structure will generate uneven temperature inside.In the field,when the temperature is contracted,the concrete body is subjected to tensile stress.Temperature cracks occur when the tensile stress exceeds the allowable tensile strength of the concrete age.In the stage of building use,the super-long concrete structure is affected by seasonal temperature and changes in ambient temperature,and it also produces hazard cracks.The anti-seepage and anti-corrosion performance of waste storage pits in waste-to-energy plants is high.Once the wall is cracked,the durability,applicability and even safety of the concrete structure will be seriously affected.Therefore,the temperature effect of the super-long concrete wall structure and its temperature are studied.Crack control measures are very important.Based on the project of Chongqing No.3 Waste Incineration Power Plant,this paper selects the super-long concrete shear wall structure of waste incineration power plant as the research object,and considers the temperature effect analysis based on the structural elastic constraints of the foundation.The main research contents and the conclusion is as follows:?1?Combined with the engineering example of waste incineration power plant,the thermal parameters and boundary conditions of concrete wall were determined.The three-dimensional solid model of super-long concrete shear wall was established by MIDAS/FEA finite element software.The numerical simulation was carried out to find the early stage of concrete shear wall pouring.Distribution of temperature field and temperature stress:The results show that the concrete temperature of the super-long concrete shear wall is about 30h,the internal temperature of the concrete reaches the peak value,and the temperature of the central pointreaches 60.9°C,which is much larger than the traditionally recognized temperature value.During the cooling stage,the cooling rate of the wall reaches 4.8°C/d,far exceeding the specified value in the specification.Due to the high temperature of the wall itself and the large exposed area,it will accelerate the development of concrete drying shrinkage and easily cause cracking of the wall.The corresponding temperature control measures should be taken.?2?After the concrete is poured,the internal temperature of the concrete is high,the inside of the wall is pressed,and the surface is pulled.During the cooling phase,the interior of the wall becomes tensile stress and increases rapidly.When the second layer is poured,the upper end of the first layer forms a constraint,which increases the temperature stress of the first layer by 10.6%and the maximum stress.Exceeding the allowable tensile strength of the concrete age,causing cracking of the wall.When the third layer wall was poured,the temperature stress of the first layer wall increased again,the increase reached9.6%,and the temperature stress at the center point of the second layer wall also increased,with an increase of 15.6%.The results show that the greater the constraint on the wall,the greater the temperature stress caused by the late temperature shrinkage and the influence of the adjacent upper layer on the lower layer.?3?Comparing the measured values of concrete on-site with theoretical calculations,it is found that the two are basically consistent,and the accuracy of numerical simulation is verified.By analyzing the influencing factors of the temperature effect of the super-long concrete shear wall,the different cement types,fly ash content,pouring temperature,restraint mode,curing conditions,wall size and layering time interval are considered.The effects of the effects and the corresponding temperature control measures are proposed.?5?It is proposed to control the temperature peak of the concrete and the temperature difference between the inside and the outside,and appropriately strengthen the concrete surface insulation and maintenance measures to reduce the shrinkage.Based on the advantages of large-volume concrete water pipe cooling technology,high temperature control speed and flexible construction,a new type of cooling water stop screw integrating the advantages of cooling water pipe and water stop screw has been developed.The numerical analysis of the three cooling effects of no cooling measures,water pipe cooling and new cooling water stop screw is carried out.At the same time,the temperature effect analysis is carried out for the wall with different thicknesses using a new cooling water stop screw,which verifies the effectiveness of the method.On the basis of this,through the numerical analysis of the cooling effect of the new cooling water stop screw pipe diameter,water flow rate,inlet water temperature and the distribution distance of the screw in the concrete wall,the different parameters are studied for the construction period.The influence effect of hydration heat on long concrete wall is described.The influence mechanism of different parameters on the hydration heat of super-long concrete wall during construction period is expounded,and the optimal cooling scheme is given.