Design method of unbonded prestress and steel plate-concrete composite reinforcement of box girder

Abstract

The invention discloses a box girder unbonded prestressing and steel plate-concrete combination reinforcing design method. The method comprises the following steps that firstly, a combination reinforcing structure is determined, specifically, the reinforced box girder unbonded prestressing and steel plate-concrete combination reinforcing structure is determined, the combination reinforcing structure comprises a steel jacket case composed of a bottom steel plate, two longitudinal side steel plates and two end blocking steel plates, and a plurality of unbonded prestressed rebars are arranged in the steel jacket case; secondly, box girder structural parameters are determined before reinforcement; and thirdly, structural parameters of the combination reinforcing structure are determined, specifically, the parameters are initialized, the theoretical maximum thickness of the reinforcing steel plates is calculated, the thickness of the reinforcing steel plates and the thickness of concrete are determined, and the height of the longitudinal side steel plates and the width of the bottom steel plate are determined. The method is simple in step, reasonable in design, convenient to implement and good in application effect, the structural parameters of the bridge combination reinforcing structure can be determined easily, conveniently and rapidly, and the designed bridge combination reinforcing structure is economical, practical and good in reinforcing effect.

Description

technical field [0001] The invention belongs to the technical field of bridge reinforcement, and in particular relates to a design method for combining unbonded prestress and steel plate-concrete reinforcement of a box girder. Background technique [0002] According to the survey in 2007, there are more than 570,000 bridges in my country, of which there are more than 98,600 dangerous bridges, accounting for about 17%. Affected by various diseases and disaster damage, resulting in a decline in carrying capacity, unable to meet the needs of transportation. It is imminent to repair and strengthen these bridge structures. Therefore, the research on bridge repair, reinforcement and transformation technology has become an important direction of bridge science and technology development. At present, the reinforcement of the upper structure of the bridge mainly adopts the methods of pasting steel plates and pasting carbon fiber cloth. During the reinforcement application process, th...

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Problems solved by technology

Although the above-mentioned external prestressed concrete reinforcement method can play the role of prestressed reinforcement to a certain extent, it has the following disadvantages: First, it is necessary to add a layer of concrete with a thickness of about 20cm to 50cm on the side or bottom of the beam. , the self-weight of the bridge increases greatly, and the appearance is irregular, which affects the appearance; second, the prestressed tendons are exposed in the air, and measures need to be taken regularly to prevent the prestressed tendons from rusting, maintenance is difficult, and the maintenance cost is high; third, the newly added The dynamic performance of prestressed tendons is poor, and shock absorbers need to be installed to reduce the resonance effect of prestressed tendons and structures; The steering block is used to realize the stress concentration at the steering block and the anchor block; once the steering block is loosened or slipped, it will cause a huge loss of prestress or even failure of the prestress; fifth, the contribution to the stiffness of the original structure is very limited

However, when using prestressed reinforcement and steel plate-concrete composite reinforcement methods to strengthen bridges, the structural design of the composite reinforcement structure is very important. Whether the reinforcement structure design is reasonable or not directly affects the reinforcement cost and reinforcement effect of the bridge. Not only the input cost is high, but the economy is poor. And it leads to unreasonable stress and poor mechanical properties of the reinforced bridge

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