单箱三室混凝土箱梁水化热试验及分析

Test and analysis on hydration of concrete three-cell box girder

为了研究单箱三室箱梁浇筑96 h内的混凝土水化热分布,浇筑了混凝土箱梁缩尺模型,在混凝土内埋置258个温度传感器,布置光电辐射传感器和风速传感器,建立了考虑太阳辐射的温度场试验模型.结果表明,单箱三室箱梁的最高温度和最大竖向温差均出现在梗腋位置处,最高温度达71.2℃,全截面最大温差达25.6℃.基于响应面分析和数值模拟,揭示了顶部土工布厚度是2个腹板竖向温差的重要影响因素,提出了不同腹板的最大竖向温差预测公式.与混凝土初始温度35℃且没有土工布覆盖的工况相比,混凝土初始温度为15℃且使用8 mm土工布覆盖,可使边腹板和中腹板的竖向温差分别降低至原工况的22.1%和24.7%.

To study the hydration heat distribution of concrete within 96 h of the casting of a three-cell box girder, a concrete box girder scale down model was cast. 258 temperature sensors were embedded in the concrete. Photoelectric radiation sensors and wind speed sensors were arranged. A temperature field test model considering solar radiation was established. The results show that the maximum temperature and the maximum vertical temperature difference of the three-cell box girder both occur at the haunch with the maximum temperature of 71.2 ℃ and the maximum temperature difference of the whole section reaching 25.6 ℃. Based on response surface analysis and numerical simulation, the thickness of the top geotextile is an important influencing factor for the vertical temperature difference of the two webs, and a prediction equation for the maximum vertical temperature difference of different webs is proposed. Compared with the working condition with an initial concrete temperature of 35 ℃ and without geotextile cover, an initial concrete temperature of 15 ℃ and an 8 mm geotextile cover can reduce the vertical temperature difference between the side webs and the middle webs to 22.1% and 24.7% under the original working condition, respectively.