预防连续箱梁施工裂缝的温度监测与有限元分析

研究混凝土浇筑初期内部温度应力不均匀分布特征和预防温度裂缝的有效措施,以西安至铜川高速公路渭河特大桥某0＃箱梁为研究对象,以MIDAS／FEA(multitier distributed applications services／finite element analysis)有限元分析软件为计算平台,采用有限单元法对施工期混凝土水化热温度场进行了数值模拟计算,分析了3种不同防裂工程措施的理论效果,并结合温度监测进行了工程措施的优化。结果表明:混凝土浇筑52h左右内部温升达到高峰,有无冷却水管的箱梁内部最高温度温差在10℃左右,在内外温差20℃左右时拆除模板时机较为恰当;箱梁腹板与横隔板交界处温度应力集中,设置冷却水管改善温度应力分布效果明显。与其他研究结果相比,采取温度监测与有限元计算全过程动态分析方法优化防裂工程措施效果较好。

Temperature monitoring and finite element analysis of preventing construction cracks in a continuous box girder

The features of uneven distribution temperature stress in recently poured concrete and the effective measures to prevent temperature cracks were studied. The 0＃ box girder in the Weihe Specially Long Bridge located in the highway from Xi’an to Tongchuan was taken as a research project, which was computed on MIDAS／FEA(multitier distributed applications services／finite element analysis)finite analysis element software. The temperature field of hydration heat of the concrete in the construction period was numerically calculated by the finite element method. The effects of three different mechanical control measures of crack control were analyzed. Combined with the results of temperature detection, the mechanical control measure was optimized.The results showed that the temperature inside the concrete rose to a peak about 52 hours after the concrete was poured, with or without cooling water pipes in the box temperature difference of the maximum temperature about 10℃.When the temperature difference between inside and outside of the concrete at 20℃ was a good time to remove the template.Temperature stress was concentrated in the junction web plate and diaphragm of the box girder, thus setting the cooling water pipes could improve the uneven distribution of temperature stress. Compared with other results, the whole process temperature monitoring and the finite element dynamic analysis by this method was better at optimizing the engineering measures of crack prevention.