Method of Strengthening Beams with Prestressed Carbon Fiber Plates

Abstract

The invention relates to a method for reinforcing a beam by using a prestressed carbon fiber board. The method comprises the following steps: fixing a tensioning end anchor base plate, a fixed end anchor base plate, a middle anchor base plate I and a middle anchor base plate II at a design position of the side surface of a to-be-reinforced beam; anchoring one end of the carbon fiber board on a carbon fiber board anchor I with a clamping bolt; clamping the carbon fiber board with a carbon fiber board anchor II, and connecting the carbon fiber board with the fixed end anchor based plate; clamping the carbon fiber board with a carbon fiber board anchor III and a carbon fiber board anchor IV, maintaining a loose state, and connecting the carbon fiber board with the middle anchor base plate I and the middle anchor base plate Il; symmetrically tensioning a steel rod with a jack, sequentially clamping and fixing the carbon fiber board anchor III and the carbon fiber board anchor IV sequentially in the tensioning process, and finally fixing the carbon fiber board anchor I; and if the jack reaches to the stroke limit, adjusting the jack to ensure the initial stroke to be zero and tensioningagain. The method can be applied to the reinforcement of a long-span bridge, and the reliable anchoring measure enables the prestressing force to be long-term effective.

Description

technical field [0001] The invention belongs to the technical field of civil engineering, and in particular relates to a method for strengthening a beam with a prestressed carbon fiber board. Background technique [0002] A large part of reinforced concrete bridges in active service have approached or exceeded their design service life. There are cracks at the bottom of the beams, corrosion of steel bars, and a tendency to accelerate the rusting, which greatly reduces the bearing capacity of the original structure and even becomes a dangerous bridge. If all these old bridges and dangerous bridges are to be demolished and rebuilt, it will inevitably bring a huge economic burden, and traffic will be interrupted during the period, affecting normal traffic operations. Prestressed carbon fiber plate reinforced bridge technology is an emerging reinforcement technology in recent years. By applying prestress to carbon fiber plate, its high tensile strength can be fully utilized and ...

AI Technical Summary

Problems solved by technology

The existing carbon fiber plate prestressed reinforced bridge technology, when the bolts are pre-embedded, the drilling position conflicts with the densely distributed stress ribs at the bottom of the beam, making it difficult to drill holes; when the span of the beam is large, the required pre-stressing force is large, The prestressed anchor points are only at both ends of the beam, which will inevitably cause excessive tension at the anchor points, resulting in failure of the connection

[0003] At present, commonly used carbon fiber plate anchors have clip-type anchors and splint-type anchors. These two types of anchors have the following defects: (1) The height of the through hole formed by the splint remains unchanged along the longitudinal direction, although the anchorage area The extrusion force is relatively large, but the extrusion force at the load-bearing end suddenly becomes zero, which makes the transverse shear stress of the load-bearing end section very large, resulting in stress concentration, and the carbon fiber plate is easily damaged by shearing or even disconnected; ( 2) Although the existing splint anchor can adjust the extrusion force distribution in the anchorage area by adjusting the bolt force to make the carbon fiber plate bear a reasonable force, it is difficult to control the change of the bolt force in actual operation; (3) the anchor The stress relaxation problem is difficult to solve. Although the splint anchor has an inner tapered hole, in theory, the clip can slide in the inner tapered hole to realize self-locking. However, a large number of experiments have proved that after the stress is relaxed, it is often The carbon fiber plate and the clip slip directly, but the clip and the inner tapered hole do not slip, so self-locking cannot actually be realized; (4) When the carbon fiber plate anchorage system is used to strengthen the beam, if the beam is under a relatively high load If the span of the beam is large or the span of the beam is large, the tensile force on the carbon fiber plate is also large. It is difficult to bear the load only by fixing the anchors at both ends of the beam. At this time, it is necessary to arrange multiple anchors at the bottom of the beam. It is used in series to share the tension, and the existing anchors can rarely achieve the function of series connection, even if some can be realized, but because the existing anchor structure itself has the problem of excessive shear force, no matter how many anchors in series tools, it is easy to cause the carbon fiber plate to be cut

The above unfavorable factors lead to poor anchoring performance of some existing anchors, and some anchorages have good anchoring performance, but their structures are complex, which brings a lot of inconvenience to production and assembly.

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