PC连续刚构桥运营阶段箱梁开裂机理及预防措施

Mechanism and Precautionary Measures for Cracking of Pre-Stressed Concrete Continuous Box Girder of Continuous and Rigid Frame Bridges in Service Phase

从温度应力、车辆荷载、砼容许主拉应力、砼疲劳、预应力损失等方面,对PC连续刚构桥在运营阶段出现的腹板斜裂缝进行了具体分析,结论是:容许主拉应力偏大、温度梯度选择不当、温度荷载及车辆荷载共同作用下的砼疲劳效应是箱梁腹板斜裂缝产生的主要原因;提出了预防开裂的措施:设计时选择适当的温度梯度;用防锈涂料对钢绞线进行防锈处理以防止因孔洞渗水对钢绞线产生的锈蚀;在各跨箱梁腹板的1/4L^3/4L之间的砼用钢纤维砼浇筑.

Based on the cracking investigation, some inclined cracks in webs apprearing in the continuous prestressed concrete box girder bridge in service phase are analyzed. Main factors inducing cracks are considered, such as temperature graclient, vehicular load, principal tensile stress of concrete, fatigue under temperature load and vehicular load. Proper temperature gradient should be selected in design phase to avoid crack. Some anti-rust coatings can be daubed on the surface of the steel strands to protect them from corrosion by cavity seepage. Webs of box girder from one quarter to three quarters of each span may be poured with steel fiber reinforced concrete to avoid fatigue effect.