PC连续箱梁桥裂缝影响因素分析

Influencing Factors Analysis on Cracking of PC Continuous Box-Girder Bridges

结合工程实桥的裂缝观测、有限元分析结果,系统研究了预应力混凝土连续箱梁桥的裂缝型式与成因、修复与加固措施,提出了防裂设计建议。首先,对连续箱梁桥典型裂缝分布现状进行了分类归纳,系统分析了裂缝产生的主要原因,对引起箱梁开裂的主要因素如纵向预应力束布置方式、竖向预应力大小、温度梯度模式等进行了敏感性分析,表明纵向预应力束布置方式和竖向预应力大小对箱梁腹板斜裂缝的开展起着主要的作用。从预应力筋布置、温度梯度模式的选取、非预应力筋的设置等几方面提出了防裂设计改进建议。

Based on cracks observation and finite element analysis of real engineering projects as well as bridge load test after reinforcement,causes and types of cracks in prestressed concrete box girder bridges and treating measurements are systematically studied.The results obtained from the calculation are presented to demonstrate the effect of sensitive factors,such as arrangement of longitudinal prestressed tendons,the magnitude of vertical prestressed force,temperature gradient,etc.The results show that the arrangement of longitudinal prestressed tendons and the magnitude of vertical prestressed force play key roles in cracks control of box girder webs.Lots of treating measurements are presented in accordance with different types of cracks;some of them are applied to a reinforcement engineering of a long span pretressed concrete continuous box girder bridge with cracks.Load test after reinforcement of the bridge demonstrates the reasonability of the treating measurements.Several design recommendations and construction measures about reinforcements and some sensitive factors mentioned above are proposed to control cracks.In accordance with the analysis of structural cracks,some conclusions are deduced： prevailing temperature stress calculation has less safety,inclined and hoop reinforcements are effective in cracking control of box girder webs.