The Bottom Slab Cracking Research Based On The Reinforcement Corrosion Of The PC Box Girder Bridge With Equal Section

The corrosive cracking of concrete caused by reinforcement corrosion is an important reason to cause failure of durability of reinforced concrete bridge structures. Especially PC box girder with equal section under the marine environment is easy to cause the corrosive crack of slab,because of the chloride concentration is higher in the marine environment, dry-wet alternate environment is obvious and slab reinforcement is more. And the study of corrosive cracking of concrete at home and abroad mainly for ordinary reinforced concrete member, the research of corrosive cracking of bridges that considering the normal operating load is little. So the research of the bridge corrosive cracking that considering the operation has great significance. This paper take a PC box girder as the support project to research longitudinal cracks in the bottom plate caused by reinforcement corrosion that have been found the most in the site investigation.1. Ansys the theory of concrete cracking caused by reinforcement corrosion. Assume the PC box girder bridge’s floor reinforcement uniform corrosion and determine the relationship between the radial displacement of concrete and rebar corrosion rate.2. Building the finite element model of PC box girder bridge with same section in normal condition by Midas Civil to analysis the maximum stress state of box girder’s normal section under normal construction and different load combinations in operation. And on the basis of the whole finite element model, an Ansys model that normal section bearing is the most unfavorable and longitudinal cracks occur most is established to ansys the transverse stress and principal tensile stress state of the beam bottom. Finally learned that the bottom structure cracks can’t produce in the normal construction and operation process. And verify the correctness that this paper mainly studies reinforcement corrosion.3. On the basis of finite element analysis in normal condition, analyse the floor stress distribution of the floor concrete, the cracking process, radial displacement and corrosion rate for different stages of cracking.(1) After reinforcement corrosion, the stress of floor concrete will increase, and the first cause the initial cracking of concrete around reinforced. Steel continue to rust and the visible cracks occur on the outer edge of the bottom plate. Then internal cracks extend outward, external cracks extend inward and finally the concrete cover was perforated vertical or diagonal by cracks.(2) When the angle area and single reinforcement corrosion happen, the radial displacement and corrosion rate that needed to cause bottom visible cracks is smaller. And it is easy to cause longitudinal visible crack.(3) When angle area reinforcement corrosion and many reinforced corrosion at the same time, the structural damage is more serious and may lead to concrete cover whole loss.4. Under the same external conditions the visible longitudinal cracks tend to produce more easily and more disadvantage for the floor crack of PC box girder with equal section when the force in the operating process is considered. So suggest to take relevant measures to control from four aspects, including material, design, construction and custody.