平塘特大桥为(249.5+2×550+249.5)m三塔双索面叠合梁斜拉桥,中塔承台于冬季施工,环境温度较低且天气变化剧烈、冷击效应明显.为避免在施工期间出现危害性裂缝,对承台大体积混凝土进行了温度控制.中塔承台分3次浇筑,施工过程中,采用了合理的混凝土配合比;对入模温度进行严格控制;在混凝土外部搭设保温棚,采用蒸汽养生等保温措施;内部设置了冷却水系统进行降温;表面、底面配制了防裂钢筋网.采用有限元软件M IDAS计算承台混凝土温度场和应力场,并在承台内部布置温度测点,对混凝土温度进行全程监测.结果表明:实测温度场的变化趋势与计算结果吻合较好,主要温度场和应力场指标均符合规范要求,大体积混凝土表面在整个浇筑养护期间均未出现明显有害裂缝.%The Pingtang Bridge is a three-tower composite girder cable-stayed bridge with double cable planes.The bridge has spans of 249.5 m,2×500 m and 249.5 m.The pile cap of the intermediate tower was constructed in winter,when the ambient temperature was low,the weath-er condition was volatile and the cold shock action was distinct.To avoid the occurrence of hazard-ous cracks during the construction period,temperature controlling measures were taken to the massive concrete of the pile cap.The pile cap of the intermediate pylon was cast by three times, and rational concrete mixing proportion was proposed.The temperature at the time the concrete was being poured into the mould was controlled.The thermal insulation shed was pitched and the thermal insulation measures like steam curing were used.Water cooling system was buried to cool down the inner temperature.And the cracking-resistant reinforcing meshes were installed on the surfaces and bases.The finite element software MIDAS was used to calculate the temperature and stress fields of the pile cap concrete,and temperature testing points were set inside the pile cap to monitor the concrete temperature during the full process.The results show that the measured vari-ation of the temperature fields matches well with the calculated results,and the indexes of the main temperature and stress fields all meet the code requirements.No obvious hazardous cracks have been observed on the surfaces of the massive concrete during the w hole casting and curing process.
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