Design method for unbonded prestress and steel-concrete combined reinforcement of concrete box girder

Abstract

The invention discloses a design method for unbonded prestress and steel-concrete combined reinforcement of a concrete box girder. The design method comprises the following steps of I, determining a combined reinforcing structure: determining the unbonded prestress and steel plate-concrete combined structure of the box girder to be reinforced wherein the combined reinforcing structure comprises a steel jacket box formed by a base steel pate, two longitudinal side steel plates and two end part plugging steel plates, and a plurality of unbonded prestressed reinforcing bars are arranged in the steel jacket box; II, determining structural parameters for reinforcing the front box girder; and III, determining structural parameters of the combined reinforcing structure in the process comprising the following steps of initializing the parameters, calculating theoretical maximum thickness of the reinforcing steel plates, determining the thickness of the reinforcing steel plates and the thickness of concrete, and determining the height of the longitudinal side steel plates and the width of the base steel plate. The method disclosed by the invention is simple in steps, reasonable in design, convenient to realize, and good in using effect, the structural parameters of the combined reinforcing structure of a bridge can be simply, conveniently and quickly determined, and the designed combined reinforcing structure of the bridge is economical and 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 the unbonded prestress and steel-concrete composite reinforcement of a concrete 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 proc...

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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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