Mechanism Analysis On Typical Diseases Of Prestressed Concrete Hollow-core Slab Bridges

Prestressed concrete hollow-core slab bridges are one of the preferred types in small and medium span bridges for their characteristics of simple form structure, convenient installation, economical construction and good applicability. However, there are some imperfections in design process, which affect the safety and durability of such bridges.In this paper, three typical diseases of the hollow-core slab bridges, the hinge joint cracking, the longitudinal cracks on the slab baseplate and the continuous slab-deck (CSD) broken diseases, are considered as the research objects. A numerical model with the so-called film structure is put forward to simulate the force transmission mechanism of the hinged joints. A calculation method which considering the vertical displacement between adjacent slabs on either side of the hinged joint to calculate the load transverse distribution coefficients is proposed correspondingly. Based on numerical simulation analysis and field test, this paper Longitudinal cracking mechanisms of the hollow-core slab is analyzed and the improved measures for design and construction are also proposed. Through fine finite element analysis on deformation and distribution characteristics of stress of CSD, a new CSD structure named the new CSD, named the arch-type CSD, is brought forward to improve its anti-breakage performance. The effectiveness of the arch-type CSD is verified through full scale test and real bridge application. Research achievements of this paper may offer theoretical reference and engineering application to bridge design and maintain management.The main works of the paper are as follows:1. A new structure form named film structure in three-dimensional finite element calculation model is developed to simulate the force transmission performance of the hinge joint by analyzing the characteristics of transverse bending deformation of the bridge and the bonding performance between hinged joints and slabs. A modified calculation method which considering vertical displacement between adjacent slabs on either side of the hinge joint to calculate the load transverse distribution coefficient is also given. Accuracy of the calculation method is thus verified.2. The transverse bending deformation of the bridge and the mechanical characteristics of the hinge joint are researched using the modified calculation method for calculating the load transverse distribution coefficient and the calculation model with film structure. Diseases formation mechanisms of the hinge joint are analyzed and the bonding failure between hinged joints and slabs is the main reason of the hinge joint cracking. On this basis, design suggestion is proposed that a square-shaped hinge joint should substitute for the traditional big-size hinge joint.3. The fine spatial finite element calculation model of the hollow-core slab bridge is also established. Studies on the structural responses under static loads and moving vehicle loadsare are launched.4. Based on numerical simulation analysis and field test, the cracking mechanisms of the longitudinal cracks are studied. The distribution law of spatial stress of the hollow-core slab is found. Thus improved measures for design and construction are put forward accordingly.5. Failure mechanism of the traditional rod-type CSD is discussed using the fine spatial finite element model. It is verified that the relative displacements of the slabs between two spans is the critical factor which leads to the CSD concrete cracks. Thereupon the arch-type CSD is brought forward. Mechanical properties comparison between the traditional CSD and the arch-type CSD is given and thus the anti-breakage effect of the arch-type CSD is confirmed.6. Based on full scale test and real bridge test, the comparison on the actual mechanical performance of the traditional CSD and the arch-type CSD is brought out. The e effectiveness of the arch-type structure is proved.