| The V-shaped pier rigid frame bridge has good mechanical performance.While improving the stiffness of the bridge structure,it effectively reduces the size of the components,thereby reducing the project cost and the height of the bridge building,making the bridge more light and beautiful;however,due to its unique structural form,the stress in the V-shaped pier and No.0 block triangular rigid frame area is extremely complex,and the hydration heat reaction of concrete is subjected to thermal expansion.The good stability of the triangular rigid frame area limits the free deformation of the structure to offset the strain generated by the hydration heat temperature,resulting in a large temperature secondary stress in the triangular rigid frame area,resulting in structural surface cracking,which seriously affects the safety and durability of the structure.Mass concrete caps,piers,zero blocks and other components appear more and more in bridge construction.During the construction process,a large amount of hydration heat is produced by the hydration heat reaction.Due to the poor thermal conductivity of concrete,the hydration heat is continuously accumulated inside the concrete,resulting in a large temperature difference between the inner surface and the surface.A large tensile stress is generated on the surface of the structure.When the tensile stress is too large,cracks appear on the outer surface,which affects the structural performance.Therefore,based on the Xingunlong Bridge in northern Myanmar,combined with the characteristics of small temperature difference and high temperature,this paper studies the hydration heat effect and temperature control measures for the cap and triangular rigid frame area of V-shaped pier rigid frame bridge.The main work and conclusions are as follows :(1)This paper introduces the theory of hydration heat effect of mass concrete.Based on this,the finite element model of V-shaped pier rigid frame bridge cap is established,and the variation law of temperature field and temperature stress is calculated.By comparing three different pile cap construction schemes,it is concluded that the cooling measures of cold water pipe can greatly reduce the internal temperature of concrete,increase the cooling rate and reduce the temperature stress.Good insulation measures can reduce the temperature difference between the inner surface of the cap and reduce the possibility of cracks.Layered pouring effectively reduces the internal temperature of each layer of concrete,but there is a narrow tensile stress band at the junction of new and old concrete.The changing ambient temperature has little effect on the inside of the cap,resulting in a sinusoidal change in the temperature difference between the inner surface,which cannot be ignored in the actual construction.The comparison between the simulated cap temperature and the actual cap temperature monitoring proves that the finite element simulation has certain reliability and provides a theoretical reference for construction.(2)The finite element software is used to establish the pile cap model,and the key factors affecting the temperature field of the pile cap are analyzed.The main conclusions are as follows : the internal temperature,surface temperature and inner surface temperature difference of the pile cap concrete are linearly related to the molding temperature,and increase with the increase of the molding temperature.For every 5 °C increase in the molding temperature,the maximum temperature inside and on the surface of the pile cap and the maximum temperature difference between the inner surface and the surface increase by about 5.15 °C,0.958 °C,4.53 °C;the greater the surface convection coefficient,the worse the insulation effect,and the greater the influence of ambient temperature on the surface of the pile cap;when the surface convection coefficient is constant,the greater the ambient temperature,the smaller the temperature difference between the inner surface of the cap;the larger the cold water pipe flow is,the lower the cooling water temperature is,the better the cooling effect is.For every 1 °C decrease in the cooling water temperature,the maximum temperature inside the cap decreases by 0.57 °C on average,but the temperature difference of the concrete around the cold water pipe increases,which is prone to cracks.Based on the above conclusions,simple temperature control measures are proposed to provide theoretical reference for engineering practice.(3)The finite element modeling analysis of the triangular rigid frame area of the V-shaped pier rigid frame bridge is carried out to study the influence of hydration heat reaction on the temperature field and temperature stress of the triangular rigid frame area after each layer of concrete pouring.The results show that there will be a tensile stress zone at the junction of new and old concrete.Before pouring into the triangular rigid frame area,each layer of V-shaped pier concrete is poured,which has a certain reduction effect on the tensile stress of the concrete junction area poured in the first two stages.After pouring the first layer of concrete of Block 0 to form a triangular rigid frame area,with the completion of the second layer of concrete pouring of Block 0 and the occurrence of hydration heat reaction,the whole triangular rigid frame area is expanded and deformed by thermal expansion.The two V legs of the V-shaped pier expand in the direction of a larger angle,and a large tensile stress of 5.11 MPa appears below the chamfer of the upper root of the V-shaped pier.At the same time,the tensile stress at the inner side of the second layer of concrete of the V-shaped pier and the junction between the outer side of the first layer of concrete and the pedestal increases,which adversely affects the entire triangular rigid frame area.Therefore,necessary measures should be taken at these positions in the design and construction of the V-shaped pier rigid frame bridge to reduce the possibility of structural cracking. |
PDF Full Text Request