Analysis And Control Practice On Mass Concrete Temperature And Stress Field Of (72+128+72)m Continuous Beam

Mass concrete generally refers to concrete with a solid structure geometry of not less than 1 m,or concrete resulting from harmful cracks due to shrinkage and temperature changes caused by hydration of the cementitious material.Mass concrete is not completely determined by the size of its absolute cross-section.It is also necessary to consider whether it will produce temperature shrinkage stress caused by hydration heat.During the hardening of mass concrete,the cement releases a large amount of heat after hydration,which causes the temperature in the central area of the concrete to rise,while the surface and boundary of the concrete are lower in temperature due to the influence of temperature,thus forming a large temperature difference on the same section.Compressive stress is generated inside the concrete,and tensile stress is generated on the surface,which causes the concrete to form cracks.In this paper,the finite element analysis software Midas Civil 2015 is used to analyze the continuous beam bridge and the bulk concrete of a new intercity railway.According to the actual situation of the project,the large-volume concrete structure model of the cap and the pier body was established,and the temperature and stress were considered according to factors such as heat source function,convection coefficient,ambient temperature,pouring temperature,concrete volume per unit volume and arrangement of cooling pipes.analysis.In the construction process of mass concrete,the temperature distribution and temperature of the inlet water are controlled to control the temperature field distribution,and the optimal water supply scheme is obtained.The temperature stress sensor is embedded in the cap and the pier body,and the temperature field and the stress field are measured.Compared with the simulation analysis results of the finite element model,the conclusions are as follows:(1)In the mass concrete,the low heat cement and the blend are used.Measures such as fly ash can effectively reduce hydration heat,but only measures to control the heat source do not allow the temperature to be controlled within the limits allowed by the specification.Therefore,it is necessary to arrange cooling water pipes in large-volume concrete to transfer the heat generated by cement hydration to the outside world in time;(2)The temperature of the mass concrete of the cap,pier and A0 block has experienced a rise and then decrease.process.The temperature and flow rate of the cooling water pipe are controlled to reduce the internal temperature of the mass concrete to below 65 °C,and the internal temperature difference is controlled within 20 °C.It is feasible to meet the specification requirements;(3)The heat source function and other parameters used in the theoretical analysis The actual concrete situation and environment have certain differences.The changes of the external environment such as temperature with time will cause the stress curve and the temperature curve to deviate from the measured values.