Method for actively reinforcing wide-span concrete case beam bridge web

Abstract

The invention relates to a reinforcing and repairing measure for existing concrete box girder bridges, and discloses a method for actively reinforcing a large-span concrete box girder bridge web plate, comprising the following steps: (1) according to the structural parameters of the concrete box girder bridge and by adopting a structural analysis method and corresponding general or special analysis software, a finite element model of a simulated reinforced plate shell concrete box girder bridge is established, thus obtaining the magnitude of the main pulling stress, the vertical stress, the longitudinal stress and the shearing stress of the box girder web plate before reinforcement and the distribution rule thereof; (2) the difference between the main pulling stress and the limited value allowed by the 'Standard' is compared to obtain the target increment value of the vertical stress of the bridge girder, and the actual reinforcement parameters are determined according to the target value; (3) drilling is carried out on the upper margin and the lower margin of the concrete box girder web plate, steel strands are installed and transversally stretched; (4) a wedge block A is used for jacking up the steel strands, then a jack is used for jacking up and pulling the steel strands to the allowed tensioning force, and the steel strands are tensioned one by one; and (5) crack is mended.

Description

Technical field: [0001] The invention relates to repair measures for existing concrete bridges, in particular to an external prestressed reinforcement repair method for the web plate of a concrete box girder bridge. Background technique: [0002] Web cracking of long-span concrete box girder bridges (continuous box girder, continuous rigid frame) is one of the problems that have been widely concerned in bridge engineering circles in recent years, and it is also a bridge disease that cannot be completely cured. The web cracking of concrete box girders generally manifests as web shear cracks, which are relatively harmful. The reasons are mostly related to the vertical prestress σ due to improper tensioning of the vertical prestressed tendons and improper anchoring structure. y The loss is too large, resulting in the main tensile stress σ tp related to overruns. Since the concrete box girder bridge has a large proportion of dead load and cannot be unloaded, it is also difficu...

AI Technical Summary

Problems solved by technology

Among them, the reinforcement method of enlarging the section, the reinforcement method of outsourcing steel plate, and the reinforcement method of sticking carbon fiber cloth (plate) all belong to the category of passive reinforcement. This method can effectively improve the ultimate strength of the structure, but it cannot improve its service stress condition. Therefore, There are many examples of cases where the concrete box girder web cracked again after the above passive reinforcement method was used.

Restricted by factors such as the structure type, it is often difficult to apply the reinforcement method of changing the structural force transmission path or the force system to the reinforcement of the web plate of the concrete box girder bridge

The prestressed reinforcement method is an active reinforcement method. This method can not only significantly improve the ultimate strength of the structure, but also effectively change the stress state of the structure and prevent the expansion of structural cracks. However, for the web of the concrete box girder , the prestressed reinforcement method has technical difficulties such as prestressed bundles (or fine-rolled threaded steel bars) have no place to anchor, tensioning equipment is difficult to lay out, and tensioning methods are not applicable, resulting in long-span concrete box girder webs due to vertical prestress After cracking, the engineering community is often at a loss; on the other hand, due to the incompleteness of the original design code ("Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts" (JTJ023-85)), construction quality, vehicle overload and other factors, Web cracking has become one of the common diseases of long-span concrete box girder bridges in my country, and it is urgent to propose and improve the method of vertical prestress reinforcement of box girder web

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