连续刚构桥高墩实心段混凝土裂缝成因分析及处理措施.pdf

连续刚构桥高墩实心段混凝土裂缝成因分析及处理措施 杜杰贵 云南大山包一级公路建设指挥部 云南 昭通 摘 要 m m C m d C C P C d d C P C P 关键词 桥墩 大体积混凝土结构 裂缝 开裂原因 膨胀剂 温度 应力 有限元法 处理措施 中图分类号 U n U 文献标志码 A文章编号 收稿日期 作者简介 E mail qq com 1 概 述 m m m m m C d m m 图 1 首节实心墩裂缝示意 d C C P C C P 2 混凝土原材料 配合比及试验 2 1 C P O HCSA C C P HCSA mm 表 1 混凝土配合比 kg m C M a m c C P M a m c 表 2 膨胀剂物理性能指标 g cm mm min min MPa d d d d HCSA 6 F O x 2 2 LVDT h C C P 图 2 C50 混凝土在恒温绝湿条件下的变形 d d C C P 3 有限元模型 D 图 3 C50 P混凝土在恒温绝湿条件下的变形 图 4 标准养护 7 d后混凝土试件干缩试验结果 表 3 标准养护条件下 C50 混凝土的力学性能试验结果 d MPa GPa MPa GPa 世界桥梁 表 4 标准养护条件下 C50 P混凝土的力学性能试验结果 d MPa GPa MPa GPa n n n cm d d cm 图 5 实心墩柱模型及温度场云图 4 裂缝成因及处理 4 1 C C cm 图 6 C50 混凝土表层 10 cm拉应力与抗拉强度计算值 C h MPa MPa C cm 图 7 C50 混凝土表层 10 cm拉应力与温度计算值 h h MPa 图 8 C50 混凝土应力发展 7 个阶段 MPa GPa C cm 图 9 C50 混凝土实心墩中心与表层 10 cm的温度及温差计算值 4 2 C P HCSA C P C P cm C P cm C P h MPa 图 10 C50 P混凝土表层 10 cm拉应力与抗拉强度计算值 图 11 C50 P混凝土表层 10 cm拉应力与温度计算值 MPa h h MPa MPa h GPa MPa HCSA C P 5 结 论 d C C P 世界桥梁 C h d d d HCSA HCSA C P 参 考 文 献 J J J J J J UEA C J C Cracking Causes Analysis and Treatments for Concrete Solid Section of High rise Pier of Continuous Rigid Frame Bridge DU Jie gui Construction Headquarters of Dashanbao Arterial Road in Yunnan Province Zhaotong China Abstract The dimension of the single column of high rise piers of a continuous rigid frame bridge measures m m each casting layer of the C concrete in the first solid section meas ures m and takes seven days of curing with mould After the mould was dismantled regular cracks were observed on the pier shaft To study the cracking causes of the high rise concrete pier and the feasibility of the treatment of adding expansion agent into the concrete standard sam ples were prepared in the laboratory to test the deformation drying shrinkage and indexes of load bearing behavior of the C concrete and the C P concrete with expansion agent under the condi tion of constant temperature and moisture insulating environment The finite element software was used to establish the model of the solid pier column to analyze the temperature history and stress development of the concrete The results demonstrate that the cracks were found on the surface of the C concrete about one day after the seven days of curing and the mould was dismantled In the restrained condition the temperature in the center of the concrete column fell down rapidly and the column experienced autogenous volume deformation shrinkage as a result the tensioning stress surpassed the tensile strength which became the main cause of concrete cracking The relative big pre compressive stress generated in the temperature rising stage of the C P concrete counteract the tensioning stress caused by temperature falling and volume shrinkage and the tensioning stress occurred after the concrete had experienced a long time of temperature falling and shrinkage and the cracking resistance of the concrete got notable increase The subsequent construction of the pier shaft of the bridge adopted the C P concrete and no cracks were found on the piers Key words pier massive concrete structure crack cracking cause expansion age