哇加滩黄河特大桥承台大体积混凝土施工温度控制

Temperature Control for Pile Cap Large Volume Concrete Construction of Wajiatan Huanghe River Bridge

青海省哇加滩黄河特大桥主桥为(104+116+560+116+104)m钢-混叠合梁斜拉桥,承台长42m、宽25.5m、高6m,为大体积混凝土结构;桥址区气温垂直分布,日夜温差较大。为避免该桥承台表面出现大面积的温度裂缝,对承台大体积混凝土施工进行温度控制。针对桥址气候特点、承台的特殊位置等因素,从原材料、混凝土配合比等方面控制混凝土入模温度和水化热总量;采用有限元软件建立承台1/4模型,根据计算结果合理布置冷却水管、制定保温方案等;通过在混凝土内布设温度传感器,对施工过程进行温度监控,并根据温度数据及时调整保温和水化热排出措施、调整混凝土内外温差。采取以上措施,承台施工完成时,未发现大面积的温度裂缝,且混凝土的温度峰值和内外温差均在规范允许值之内。

The main bridge of Wajiatan Huanghe River Bridge in Qinghai province is a steelconcrete composite girder cable-stayed bridge with span arrangement of（104＋116＋560＋116＋104）m.The pile caps are large volume concrete structures with dimension of 42m×22.5m,6m in height.The ambient temperature at the bridge site is vertically distributed with great difference during day and night.To avoid the presence of considerable temperature cracking on the pile cap surface,temperature control was carried out for the large volume concrete construction of the pile caps.In light of the climate characteristics at the bridge site and the location of the pile caps,the mould-entering temperature and total amount of hydration heat were controlled from aspects of raw materials and concrete mixing proportion.The finite element software was used to establish the1∶4scale model of the pile cape for the simulation analysis.According to the calculation results,the cooling water pipes were rationally arranged and thermal isolation scheme were determined.By setting temperature gauges in the concrete,the temperature monitoring and control for the construction was done.And according to the temperature data,the thermal isolation and hydration heat dissipating measures were revised,and the inner and outer temperature difference of the concrete was adjusted.The results of the temperature control indicate that no large area of temperature cracking was found after the completion of pile cap construction,and the temperature crest value and the inner and outer temperature difference of the concrete were all within the allowed range prescribed in the code.