The Experiment And Application Of Reinforced Concrete Beam Using Double Prestressed Carbon Fiber Plate

With the constant improvement of China's transportation infrastructure,infrastructure slows the pace of building and road bridges in our country gradually entered the stage of maintenance.Due to the Natural aging and rapid increase of traffic volume,some bridges engender overload phenomenon and it needs reliable strengthening technology for the problematic bridge reinforcement.Compared with passive reinforcement technology such as stuck steel,strengthening technology with prestressed carbon fiber plate because its construction technology is simple and reinforcement effect is good,it will be the future developing direction of the bridge reinforcement.In the practice of bridge reinforcement,the more hollow slabs(including precast slab and the overall site casting)exist some birth defects such as insufficient bottom thickness and too much cavity.Due to various reasons,it needs to be strengthened with prestressed carbon fiber plate.Therefore we must set anchorage block on the bottom slab,and set the pressure plate(press carbon fiber plate tightly and keep good bonding with concrete surface).However in the hole or insufficient thickness of base plate is unable to meet this requirement.High prestressed carbon fiber plate bridges' reinforcement can improve the bridge stiffness efficiently,improve the bending load capacity of the bridge and reduce the development of cracks.But the anchoring ability of the high prestressed carbon fiber is the difficult point in this technology.In this paper,the waveform of tooth fixture can anchor with the condition of the high prestressed carbon fiber board,and can clamp double-layer or multi-layer carbon fiber.Because of its simple construction technology,and it can be applied within a small space at the bottom of the beam,it has a great advantage in the bridge reinforcement.So in the actual hollow slab reinforcement,the position that can for the anchorage and fixing of prestressed carbon fiber plate is not bounteous.So our research team developed a kind of waveform that can clamp 2 layers of carbon fiber board,developed strengthening process for two-layer prestressed carbon fiber board,specially designed T-beam reinforcement test using two-layer prestressed carbon fiber plate and verify the feasibility of this double prestressed carbon fiber plate reinforcementtechnology.Experimental study shows that the strengthening technology with double prestressed carbon fiber board is reliable and reinforcement effect is obvious.On the basis of the test study that use double prestressed carbon fiber board to reinforce T beams,our team successfully applied this technological achievement to the cast-in-place of the whole plate-girder reinforcement in Chong Qing YunYang TangXi river and the reinforcement is the first example of double prestressed carbon fiber plate reinforcement application in the world.Bridge in Chong Qing YunYang TangXi river is an ordinary concrete cast-in-place whole plate-girder.Due to the poor quality of construction,there are a large number of empty,a serious shortage of plate thickness,rebar corrosion that in the bottom plate is serious and identified fourth type of bridge.And strengthen treatment must be carried out.Although the bridge is a whole plate,bottom plate is wide,and it could theoretically decorate with a article number of the prestressed carbon fiber plate to reinforce.But because of the existence of holes and the insufficient thickness of the bottom plate,in the position of the cavity can't set the anchor bolt,so the actual location of the prestressed carbon fiber board is very limited,only in the web(or floor)corresponding to the bottom position can set prestressed carbon fiber plate.In order to improve the bearing capacity of the bridge more effectively,double prestressed carbon fiber plate reinforcement scheme is designed.Each prestressed carbon fiber plate is made of two layers of(50x2)mm carbon fiber plate and use the tailor-made waveform anchor for anchoring at the end.The tension control stress of each prestressed carbon fiber plate is 1000 MPa,pretension is 200 kN,whole bridge were decorated with 10 double prestressed carbon fiber sheets,and a total of pretension is 2000 kN.Reinforcement calculation shows that after using this design scheme,substantially increase the ultimate bearing capacity of the original bridge,but also improve the cracking with prestressed.Load test also indicated that after strengthening reinforcement with double prestressed carbon fiber plate,the stiffness and strength of the bridge are greatly increased,meet the standard of load,and achieve the anticipated reinforcement.Adopt double prestressed carbon fiber for the reinforcement of Chong Qing YunYang TangXi river bridge is successful,and it provided a new efficient prestressed reinforcement method on the insufficient thickness hollow plate-girder that on the base,also created the double prestressed carbon fiber plate reinforcement project,is worth promoting.