郑州黄河公铁两用桥大体积承台裂纹控制技术

郑州黄河公铁两用桥主桥第一联为(121+5×168+121)m单索面连续钢桁结合梁斜拉桥,第二联为(121+3×120+121)m连续钢桁结合梁桥。该桥承台为大体积混凝土结构,为避免大体积混凝土出现裂纹,以主桥6号墩承台为研究对象,分析裂纹产生的主要原因,提出施工中控制裂纹产生的相应措施:首先通过试验选择混凝土的最优配合比;通过对承台有限元模型进行热工计算分析,得出合理的冷却水管布设方案及温度测点布设方式;严格控制混凝土浇筑时的分层厚度;采用"外部保温、内部降温"的冬季养护原则进行养护,并实时测量各测点温度。结果表明:该承台养护完成后,表面未出现任何裂纹,实现了大体积混凝土裂纹的有效控制。

Technique of Crack Control for Large Volume Pile Cap of Zhengzhou Huanghe River Rail-cum-Road Bridge

The first continuous unit of the main bridge of Zhengzhou Huanghe River Rail-cum-Road Bridge is a(121+5×168+121) m single cable plane continuous steel truss composite girder cable-stayed bridge.The second continuous unit is a(121+3×120+121) m continuous steel truss composite girder bridge.The pile cap of the bridge is of large volume concrete structure.To prevent cracks in the large volume concrete,the pile cap of No.6 pier is taken as study object.Through the analysis of the main causes of cracks,the corresponding crack control measures in construction are proposed: that is,First,to select optimum mixing proportion of concrete through test;to get the reasonable layout scheme of cooling water pipes and the distribution of the temperature testing points through the thermal calculation analysis on the finite element model of the pile cap;to strictly control the thickness of stratification during the casting of concrete;to carry out maintenance based on the winter maintenance principle of "keeping warm outside,decrease temperature inside",and to measure the real time temperature of the testing points.The results indicate that no cracks occur on the surface of the pile cap after maintenance and the effective control of cracks on large volume concrete is realized.