Test & Study On Strengthening Method For The Deck Of Steel Box Girder Bridge

Since the reform and opening up,China has built more than twenty seats long-span cable-stayed bridge or the suspension bridge with steel box girder. Along with the growth of bridge duty time, the steel deck pavement and steel deck itself all appeared fatigue damaged and crack disease,because of the volume of traffic growth quickly and the increase in heavy-load or overload vehicles and other factors.Because the deck of steel box girder is special, so at present, we can do only a few welding work for those expansion crack that have detected, or to replace some local component. but cannot solve diseases about the deck of steel box girder fundamentally, And until now, we haven't better measures to stop the tiny cracks and micro traumatic disease haven't found temporarily to further expand.Considered mainly steel box girder cracks produced in weld, So in order to reduce steel box girder crack, improving the capability of anti-fatigue about weld and the total stiffness of steel box girder is the key.In this paper, we focused on reinforcement works about the North River Bridge in Guangdong Mafang. By improving the structure of the deck or pavement of bridge, thereby enhancing the stiffness of the bridge panel, reducing the stress and deformation come from various parts of the deck of orthotropic steel box bridge in order to improve its anti-fatigue strength. two kinds of reinforcement methods were studied and compared, one is polymer modified cement concrete pavement method, the other is Sandwich Plate System with Steel Plate (SPS). The following conclusions can be obtained through material testing, visual inspection, bridge line tracking test , bridge static load test, finite element analysis and so on.(1) Inspection about the appearance of the bridge can found that the most fatigue damage of steel box bridge cracks is weldcrack, we can see that the weld is the weakest part to resist fatigue.(2) Sandwich Plate System with Steel Plate (SPS) testing result show that this material properties of the indicators is good. Thus, this material can be applied to reinforced the deck of steel bridge.(3) Through the bridge static load test ,we can found that the local stress of steel orthotropic deck have dropped significantly after it is reinforced. In contrast, polymer concrete paving program to improve the results slightly better.(4) Through finite element analysis about the deck of bridge system, the fatigue cracks where the longitudinal ribs and transverse ribs connected because of stress concentration that caused by the automobile wheel load. Using reasonable deck pavement can reduce the local stress.In conclusion,both methods described in this paper can effectively reduce the stress and deformation of the deck . According to load test and finite element analysis, we find the method about polymer modified cement concrete pavement program is better. However, the durability of both reinforcement and practical effects still need long-term&follow-up observations& further study.