单室箱梁电热器养护温度场及温度应力分析

Study on temperature field and temperature stress of single-cell box girder cured with electric heater

考虑工期及场地原因,为提高重型箱梁的现场预制效率,采用箱梁孔内布置电热器对梁体加热,外部覆盖保温层的养护方法;基于热量传导理论使用有限元软件Abaqus,模拟现场工况,建立有限元分析模型对箱梁温度场和应力场进行数值分析,并与实测数据进行对比。表明箱梁水化热反应剧烈,经历了较短的升温阶段达到峰值后缓慢降温,所采用的数值分析方法可以真实反应该养护下的箱梁混凝土水化热温度场;温度应力发展达到峰值后减小,其温度应力峰值未超过混凝土抗拉强度。混凝土试块试验结果表明箱梁的抗压强度和弹性模量达到施加预应力的要求。该养护方法确保了现场预制箱梁的安全、高效。

Considering the factors of construction period and site, in order to improve the precast efficiency of box girders with heavy weight, the electric heater was installed in the cell of the box girders to heat, and at the same time the surface of single-cell box girder was covered with insulating layer to cure the concrete. Based on the theory of heat transfer, a finite element analysis model was built with Abaqus to simulate the working conditions of construction site. The temperature field and the temperature stress field were numerically analyzed and compared with the actual measurement datum. The results showed that the hydration process developed fast. The temperatures of the box girders experienced a phase of rapid rise and then the temperatures of the single-cell box girder reached the peak. Finally, a slow cooling phase was observed in the temperature field. It was proved that the numerical analysis can describe the actual concrete hydration heat temperature field of the box girders under the curing accurately by comparing with the measurement datum. Temperature stress of single-cell box girders decreased after the peak value, which was less than the tensile strength of concrete. The results of concrete specimens test show that the requirements of prestressing on compressive strength and elastic modulus of single-cell box girders can be met by the proposed curing method. It can be concluded that security and efficiency of precasting single-cell box girder can be guaranteed by this curing method.