Analysis And Control Of Non-loaded Cracks On The Top Of Pier For PC Continuous Rigid Frame Bridge

Bridge is the important component element of communications and transport, is the major matter foundation of human society's progress. With the booming development of prestressed concrete continuous rigid frame bridge, cracks of box girder are paid more and more attention. Especially, structure cracks by non-loaded facts have come into research man's high degree notice, because of the complicated causes and serious harm to the bridge structure's durability.Because of the bad heat conduction of the concrete material, prestressed concrete bridges are subject to varied temperature actions, which can make notable influence on the transformation and stress of bridge structures. With the span of continuous rigid frame bridge gradually increase, grade of box girder structures'concrete become higher and higher to meet the need of high strength, and the concretes'volume and dosage became more and more huge, especially for top of main pier NO.0 block. No.0 box girder is the bearing structure of continuous rigid frame bridge, has not only huge volume, but also very complex composition and stress state. It usually appear craze phenomenon when afford varied non-loader facts. Mass concretes of NO.0 box girder release hydration heat in the hardening process, which will cause non-homogeneous distribution of temperature fields, and comparatively large temperature discrepancy in different position of box girder. Meanwhile, when poured in different layers, under layer concretes will restrict upper layers. In base of these, temperature and constrains stress appear which is the main reason of concrete cracks. Such non-loaded cracks influence the integrity and durability of the bridge badly, must be controlled.After consulting lots of professional theories and academic articles, this paper analyze on theory to the feature of PC continuous rigid frame bridge, classification and work principle of box girder cracks, sensibility facts cause box girder craze. While, all the following analysis is on the basis of a continuous rigid frame bridge in Guangxi Wuzhou whose main span is 145 meters. We collect and research box girder's observation temperature fields and stress distribution accompany the construction process of NO.0 block poured by different layers. According to the thermodynamics theory and finite element method, use MIDAS Civil to build the finite element entity model of NO.0 block and first-block which poured by different layers, imitation analyze hydration heat temperature fields and stress distribution. To combine the observation data analysis, the paper puts forward to find the cause of NO.0 box girder non-loaded cracks and control, and provides reference information to similar bridges' cracks cure.